Senior EMC engineer wanted.
Posted on behalf of a non-subscriber. Richard Nute . There has never been a better time to join Apple Computer. Apple is working to create new solutions and technologies that could equal or exceed the impact of the Macintosh. Fact is, the company that started the personal computer revolution is once again on the threshold of redefining an entire industry. Come and join us in the following position: SENIOR EMC ENGINEER Responsibilities include electrical and mechanical design evaluations, circuit design, and test to FCC part 15, CISPR 22, EN Immunity requirements. Must understand good EMC design practices, and be familiar with global EMC requirements. 5+ years of EMC experience, and a BSEE or equivalent education is needed. We offer a great compensation package. Relocation may be provided. For immediate consideration, please send your resume (e-mail or fax preferred) to: Apple Computer 1 Infinite Loop Cupertino, CA 95014 Attention: Brenda Barnes techj...@apple.com fax 408-862-8192 voice 408-974-7807 . - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: NRTL Listing
Hi Joe: > liability and such. Can anyone share some more info as to their reasons for > listing or not listing such a product which is well below hazardous limits. There are two schools of thought: 1. Because of its low-voltage supply, the unit is exempt from most safety certifications throughout the world. Therefore, there is no need to obtain any safety certifications. 2. Regardless of being exempt, customers expect most electrical products to bear safety certification marks. Indeed, OSHA and NEC electrical inspectors (and customs inspectors) cannot make field judgements as to whether an electrical product is exempt from safety certification. The presence of the marks assure acceptance without your intervention. I suggest that the decision should be based on your customer base, where the product is used, your company, the product, and the possible difficulties you might encounter without the marks. Any difficulties will have a cost in (1) delaying the product to the customer, and (2) your time to resolve, for the various inspectors, the fact that the product does not require the safety certification. For example, low-voltage products going into the home are not likely to be subject to discrimination due to safety certification marks. On the other hand, products going into the workplace, being part of an electrical installation, or going across borders may very well be subject to inspection for certification marks. Have fun! Rich - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: voltage on Neutral line
Hi Moshe: The voltage of the neutral with respect to the ground wire is a function of its resistance and its current: E = I * R Maximum normal current is the rating of the fuse or circuit- breaker protecting that particular circuit. For a 120-volt circuit in the USA and Canada, the current would be either 15 or 20 amperes. The resistance is a function of the wire cross-sectional area and its length. According to a licensed electrical engineer colleague, circuits in the USA are designed for a maximum 6% voltage drop, preferably 3% voltage drop at the load. This means that the voltage drop across the neutral from the load to the distribution transformer is 3% maximum, 1.5% preferable. So, the resistance is selected according to maximum voltage drop at the circuit rating. The answer to your question is that the neutral voltage varies from zero to 1.5% nominal, 3% maximum, of the supply voltage depending on load. It further varies with the distance of the point of interest from the point where the neutral is grounded. If the point of interest is within a few feet of the point where the neutral is grounded, then the neutral voltage will be a fraction of a percent. If the point of interest is near the maximum distance from the grounding point, and if the load is also at that point, then the neutral voltage will approach 1.5% nominal to 3% maximum. Fault current is a function of time. Overcurrent devices will operate according to their time-current curves. So, if you know the fault current, then you can calculate the voltage at any point along the neutral according to where the fault current is introduced and where the neutral is grounded. Fault current exists only for the period of time it takes to operate the overcurrent device (I-T curve). For a 120-volt system, you can expect about 1.8 volts drop nominal, 3.6 volts maximum, assuming a single, maximum load furthest from the point of grounding, and your measurement is also at that point. Best regards, Rich - Richard Nute Product Safety Engineer Hewlett-Packard Company Product Regulations Group AiO Division Tel : +1 858 655 3329 16399 West Bernardo Drive FAX : +1 858 655 4979 San Diego, California 92127 e-mail: ri...@sdd.hp.com - - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Safety Incident Reporting
Hi Richard: At one time, The Conference Board put out some very good material about handling safety incidents. I'm not sure it is still available, and I am not sure how to contact them. (They were in the news recently -- they do a lot of stuff!) Best regards from San Diego, Rich - Richard Nute Product Safety Engineer Hewlett-Packard Company Product Regulations Group AiO Division Tel : +1 858 655 3329 16399 West Bernardo Drive FAX : +1 858 655 4979 San Diego, California 92127 e-mail: ri...@sdd.hp.com - - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Follow Up Services/Factory Inspections
Hi Tania: I, too, have had the same inspection experiences (saw a transformer and prove solder time-temperature). In the case of the transformer, I offered to take the inspector to the transformer manufacturing plant to make the measurments during the manufacturing process. The particular transformer was not in production that day. So, I set up a day when the transformer would be in production. The inspector didn't show up, and never asked the question again. By the way, the unwritten rule is that a product or component is not required to be destroyed as a part of the inspection. Many inspectors are not aware of this rule. I had a construction where a component was installed in such a way that to remove it would cause damage to several other parts, rendering the product unsalable. The inspector insisted upon seeing the actual part; I refused. I did show the uninstalled part to the inspector. Nevertheless, it was an impasse, but we did not get a VN. Best regards, Rich - Richard Nute Product Safety Engineer Hewlett-Packard Company Product Regulations Group AiO Division Tel : +1 858 655 3329 16399 West Bernardo Drive FAX : +1 858 655 4979 San Diego, California 92127 e-mail: ri...@sdd.hp.com - - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Sr. Compliance/Reliability Engineer - PMCG
Posted on behalf of Gary Jong: -- I'm the Staffing Manager for the Philips Mobile Computing Group (PMCG) PMCG designs and develops new generations of the award winning Velo and other mobile computing and communications platforms based on the Windows CE operating system. We have a current opening for a Senior Compliance and Reliability Engineer who will work closely with Electrical, Mechanical, and Manufacturing Engineering teams to help design and develop new generations of our products. The individual in this role will also interface with the Marketing and Operations groups to ensure regional requirements are met and manufacturing needs are fulfilled. We're looking for someone who is degreed in a relevant technical area with a thorough understanding of UL 1950, EN 60950, the CB Process, MBTF, ALT and MIL-STD-810. Responsibilities will include, but are not limited to: - Design recommendations, material and component selection, test plan development, testing, troubleshooting, report generation, and coordination of agency submittals for Worldwide Product Safety and Product Reliability Plan fulfillment. - Conduct testing at our in-house facilities as well as coordinating and attending testing at local and international test facilities, prepare test plans, record results, and relay applicable information back to the design, marketing, and operations teams. - Oversee Accelerated Life testing and evaluation of the reliability program implementation for several product lines. - Be responsible for developing in house and third party reliability specifications, supervising the testing, and compiling the test data, and report generation. - Develop a working relationship with local and international Product Safety test facilities and track Worldwide Product Safety Standards and Country specific requirements. - Interface with the product manufacturers to ensure inspections are concluded without issue. - Coordinate with Philips internal documentation for production materials, critical components, product labels, and manual statements. If you are interested in and qualified for such an opportunity, I'd be happy to follow up promptly with you and provide additional information. I look forward to your reponse! Regards, Gary Jong Staffing Manager Philips Silicon Valley Center ga...@pmc.philips.com - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Video protocols..
Hi George: > Pal is primarily used throughout Europe and NTSC is used in USA, Canada, > Mexico and Japan. > > Does anyone know of any other countries that may use NTSC ? Check out the following web sites: http://www.bbc.co.uk/aberdeen/eng_info/world_tv_standards.shtml http://www.ee.surrey.ac.uk/Contrib/WorldTV/ http://kropla.com/tv.htm Best regards, Rich - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Inherently Limited power source..
Hi George: > Could someone give me an explanation of what makes a power source > "Inherently Limited".. Others have provided excellent responses to your question. Perhaps I can embellish their answers. A doorbell transformer is the prime example of an inherently limited power source. The requirements originally were published in the National Electrical Code, Article 725. They were picked up by UL in many of their standards. Now, the NEC makes reference to one of those UL standards, UL 1950, as the authoritative source for Limited Power, both inherently limited and not inherently limited. The simple answer to your question is: Any source that meets the requirements and does not use a fuse. So, electronic circuits that limit the power (under both normal and single-fault conditions) without reliance on a fuse are deemed "inherently limited." Inherently limited circuits need not be limited by an impedance, although that has been the tradition. Best regards, Rich - Richard Nute Product Safety Engineer Hewlett-Packard Company Product Regulations Group AiO Division Tel : +1 858 655 3329 16399 West Bernardo Drive FAX : +1 858 655 4979 San Diego, California 92127 e-mail: ri...@sdd.hp.com - - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: IEC 364 - Definition of SELV
Hi Kevin: > Is IEC 536 the base document for the definition of SELV? > (where it says that "SELV" means "Safety Extra-Low Voltage")? Yes. IEC 536, Definitions, Sub-clause 2.6: "Safety extra-low voltage (SELV)" HISTORY LESSON == Prior to IEC 536, I believe SELV was not defined as such, but the concept of SELV, i.e., low voltage protected from higher voltages did indeed exist. CEE Publication 10, Electric Motor-Operated Appliances, October, 1964, has the following definition: "Extra-low voltage denotes a nominal voltage not exceeding 42 V between conductors and between conductors and earth, the no-load voltage not exceeding 50 V. "When extra-low voltage is obtained from the supply mains, it must be through a safety isolating transformer or a converter with separate windings." Due to its similarity with the definition from IEC 536, it appears this CEE 10 ELV definition evolved to SELV. CEE: International Commission on Rules for the Approval of Electrical Equipment. (I believe the CEE was absorbed by CEN and CENELEC.) CEE Members: Austria, Belgium, Czechoslovakia, Denmark, Germany (FR), Finalnd, France, Greece, Hungary, Italy, Netherlands, Norway, Poland, Spain, Sweden, Switzerland, United Kingdom, Yugoslavia. Best regards, Rich > From owner-emc-p...@majordomo.ieee.org Tue Oct 26 23:44:11 PDT 1999 > Received: from hpsdlo.sdd.hp.com (hpsdlo-sw.sdd.hp.com [15.80.36.40]) by > hpsdlfsg.sdd.hp.com with ESMTP (8.7.6/8.7.3 TIS 5.0/sdd epg) id XAA23435 for > ; Tue, 26 Oct 1999 23:44:11 -0700 (PDT) > Received: from ruebert.ieee.org (ruebert.ieee.org [199.172.136.3]) > by hpsdlo.sdd.hp.com (8.8.6 (PHNE_14041)/8.8.5btis+epg) with ESMTP id > XAA04752 > for ; Tue, 26 Oct 1999 23:44:09 -0700 (PDT) > Received: by ruebert.ieee.org (8.8.8+Sun/8.8.8) > id CAA20446; Wed, 27 Oct 1999 02:19:26 -0400 (EDT) > Date: Wed, 27 Oct 1999 02:18:15 -0400 > From: Kevin Richardson > Subject: Re: IEC 364 - Definition of SELV > To: Rich Nute > Cc: "[unknown]" > Message-ID: <199910270218_mc2-8a97-1...@compuserve.com> > MIME-Version: 1.0 > Content-Type: text/plain; >charset=ISO-8859-1 > Content-Disposition: inline > Content-Transfer-Encoding: 8bit > X-MIME-Autoconverted: from quoted-printable to 8bit by ruebert.ieee.org id > CAA20443 > Sender: owner-emc-p...@majordomo.ieee.org > Precedence: bulk > Reply-To: Kevin Richardson > X-Resent-To: Multiple Recipients > X-Listname: emc-pstc > X-Info: Help requests to emc-pstc-requ...@majordomo.ieee.org > X-Info: [Un]Subscribe requests to majord...@majordomo.ieee.org > X-Moderator-Address: emc-pstc-appro...@majordomo.ieee.org > > > Hi Rich, > > Thank you for devoting so much time to reply. This is just what I needed. > I am familiar with IEC 60950 and I wanted to be able to compare the > definitions. Thank you. > > One other question to Rich or anyone else that can help. > > Is IEC 536 the base document for the definition of SELV? In addition to > how SELV is expressed in IEC 364 I am also trying to confirm the base > standard in the IEC responsible for the SELV definition. Is it IEC 536 or > some other document? In which standard or guide is the term SELV spelt out > (where it says that "SELV" means "Safety Extra-Low Voltage")? There must > be a base IEC document somewhere that defines the term. > > Best regards, > Kevin > > > > > Hi Kevin: > > > > > > > Can anyone please provide the SELV definition from IEC 364? > > > > I'm working from some old documents, but... > > > > SELV is not expressly defined in IEC 364-4-41. Instead, > > it specifies "Protection by safety extra-low voltage." > > > > It says: > > > > "Protection against electric shock in normal service > > and in case of a fault is deemed to be ensured when: > > > > - the nominal voltage cannot exceed the upper limit > > of Voltage Band I*, > > > > - the supply is from one of the safety sources listed > > in Sub-clause 411.1.2, and > > > > - the conditions of Sub-clause 411.1.3 are fulfilled." > > > > "*See IEC Publication 449: Voltage Bands for Electrical > > Installations of Buildings." > > > > The safety sources are: > > > > - a safety isolating transformer, > > > > - a source of current providing a degree o
Re: IEC 364 - Definition of SELV
Hi Kevin: > Can anyone please provide the SELV definition from IEC 364? I'm working from some old documents, but... SELV is not expressly defined in IEC 364-4-41. Instead, it specifies "Protection by safety extra-low voltage." It says: "Protection against electric shock in normal service and in case of a fault is deemed to be ensured when: - the nominal voltage cannot exceed the upper limit of Voltage Band I*, - the supply is from one of the safety sources listed in Sub-clause 411.1.2, and - the conditions of Sub-clause 411.1.3 are fulfilled." "*See IEC Publication 449: Voltage Bands for Electrical Installations of Buildings." The safety sources are: - a safety isolating transformer, - a source of current providing a degree of safety equivalent to that of the safety isolating transformer (e.g., motor generators with windings providing equivalent isolation), - an electrochemical source (e.g., a battery) or another source independent of a higher-voltage circuit (e.g., a diesel-driven generator, - certain electronic devices complying with appropriate standards where measure have been taken to ensure that, even in the case of aninternal fault, the voltage at the outgoing termainals cannot exceed the values specified in Sub-clause 411.1.1. The definition of SELV appears in IEC 536: "A voltage which does not exceed 50 V ac rms between conductors, or between any conductor and earth, in a circuit which is isolated from the supply mains by means such as a safety isolating transformer or converter with separate windings." IEC 950 defines SELV CIRCUIT: "A secondary circuit which is so designed and protected that under normal and single fault conditions, its voltages do not exceed a safe value." SELV is a special case of ELV, Extra Low Voltage. ELV is defined (or implied) as a maximum voltage value deemed not to cause an electric shock. SELV applies to an ELV where, in the absence of specific protective mechanisms, the ELV would exceed ELV under fault conditions. So, SELV implies ELV with some means to prevent the voltage from exceeding ELV limits in the event of a fault. A single-insulated transformer ELV secondary is ELV. A double-insulated transformer ELV secondary is SELV. An ELV battery is ELV. It may or may not be SELV, depending on your point of view. 1: Since the battery itself cannot exceed ELV under single- fault conditions, then it cannot be SELV. Or, 2: Since the battery itself cannot exceed ELV cannot exceed ELV under single-fault conditions, then it must be SELV. However, as defined, SELV implies an included protective mechanism to limit the voltage in the event of a fault. SELV also implies that the ELV is derived from a higher, non-ELV source. If you accept that a battery is ELV, then the safety standards require that the battery voltages cannot be touched! Best regards, Rich - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: internet information
Hi Laura: > Could someone please tell me where previous EMC and safety discussions are > posted on the internet. emc-pstc messages are archived at: http://www.rcic.com/ Click on "Virual Conference Hall." The archives can be searched by topic. > Also I am interested to know if a detachable UK power Cord is required to be > fused. Products using this line cord have integral fuses in both AC lines. Yes. The UK uses a "ring" wiring scheme such that the installation overcurrent protection cannot protect the power cord wires as is done in the North America branch wiring scheme. Therefore, to protect the power cord from overcurrent, the plug must include a fuse. (The plug fuse does NOT protect the load from overcurrent; this is a function of the product fuse.) Best regards, Rich - Richard Nute Product Safety Engineer Hewlett-Packard Company Product Regulations Group AiO Division Tel : +1 858 655 3329 16399 West Bernardo Drive FAX : +1 858 655 4979 San Diego, California 92127 e-mail: ri...@sdd.hp.com - > From owner-emc-p...@ieee.org Tue Nov 16 16:57:16 PST 1999 > Received: from hpsdlo.sdd.hp.com (hpsdlo-sw.sdd.hp.com [15.80.36.40]) by > hpsdlfsg.sdd.hp.com with ESMTP (8.7.6/8.7.3 TIS 5.0/sdd epg) id QAA06833 for > ; Tue, 16 Nov 1999 16:57:15 -0800 (PST) > Received: from ruebert.ieee.org (ruebert.ieee.org [199.172.136.3]) > by hpsdlo.sdd.hp.com (8.8.6 (PHNE_14041)/8.8.5btis+epg) with ESMTP id > QAA21254 > for ; Tue, 16 Nov 1999 16:57:12 -0800 (PST) > Received: by ruebert.ieee.org (8.9.3/8.9.3)id TAA00362; Tue, 16 > Nov 1999 19:39:36 -0500 (EST) > Message-ID: <7798e57399e3d211b116009027626952400...@lvexch1.lvl.hach.com> > From: Laura Leyba-Newton > To: "'emc-p...@ieee.org'" > Subject: internet information > Date: Tue, 16 Nov 1999 11:36:06 -0700 > MIME-Version: 1.0 > X-Mailer: Internet Mail Service (5.5.2448.0) > Content-Type: text/plain; > charset="iso-8859-1" > Sender: owner-emc-p...@ieee.org > Precedence: bulk > Reply-To: Laura Leyba-Newton > X-Resent-To: Multiple Recipients > X-Listname: emc-pstc > X-Info: Help requests to emc-pstc-requ...@majordomo.ieee.org > X-Info: [Un]Subscribe requests to majord...@majordomo.ieee.org > X-Moderator-Address: emc-pstc-appro...@majordomo.ieee.org > > > Could someone please tell me where previous EMC and safety discussions are > posted on the internet. > Also I am interested to know if a detachable UK power Cord is required to be > fused. Products using this line cord have integral fuses in both AC lines. > You help would be greatly appreciated. > -Laura > > > - > This message is coming from the emc-pstc discussion list. > To cancel your subscription, send mail to majord...@ieee.org > with the single line: "unsubscribe emc-pstc" (without the > quotes). For help, send mail to ed.pr...@cubic.com, > jim_bac...@monarch.com, ri...@sdd.hp.com, or > roger.volgst...@compaq.com (the list administrators). > > > - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: impact /probes
> BTW, you may find a 50mm diameter ball bearing, but will it weigh 500g > +/-25g? And then you'l have to drill and tap it for an eyelet for the > string. The impact ball spec was written around a 2-inch diameter ball bearing. Drilling and tapping the ball bearing requires some sort of arc-drilling equipment (because of the hardness of the ball bearing). Best regards, Rich - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Warnings (humor)
These are actual warnings on products... On a large folding cardboard sunshade for car windscreens: "Do not attempt to operate vehicle with sunshade in place." In a VCR manual section about time recording programs: "Only events in the future can be recorded on this machine, not in the past. Resetting the clock to an earlier time will not accurately record past events." On a car lock which loops around both the clutch pedal and the steering wheel: "Warning -- Remove lock before driving." On a packet of juggling balls: "This product contains small granules under 3 millimeters. Not suitable for children under the age of 14 years in Europe or 8 years in the USA." On a packet of Nytol sleeping tablets: "Warning: may cause drowsiness." On a packet of peanuts served on an internal flight in China (written in both English and Chinese): "Open packet and eat contents." On 500g packets of Sainsbury's peanuts: "Contains nuts." Seen on a camera: "This camera only works when there is a film inside." On a bottle of flavored milk drink: "After opening, keep upright." On a can of windscreen de-icing spray: "Spray works in sub-zero temperatures." On a can of insect spray: "Kills all kinds of insects! Warning: This spray is harmful to bees." A different brand of insect spray: "Kills flies, wasps, mosquitoes, midges, and other flying insects. Not tested on animals." On an ocean buoy for determining the position of submarines: "Protect from seawater." On a Halloween Batman costume: "This cape does not give the wearer the ability to fly. On a Rowenta iron: "Warning! Never iron clothes on the body!" In the instructions for a Korean kitchen knife: "Keep out of children." On the "CycleAware" helmet-mounted mirror: "Remember: Objects in the mirror are actually behind you." Best wishes for the New Year, Rich ps: For colleagues in the USA... Nominated for quote of the year is the statement made by Representative Dick Armey who, when asked if he were in the President's place would he resign, responded: "If I were in the President's place I would not get a chance to resign. I would be lying in a pool of my own blood hearing Mrs. Armey standing over me saying, 'How do I reload this damned thing?'" - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: UL1950 Overvoltage Tests
Hi Doug: > Isn't this a variation of using the traces as a fusing element > instead of using a real fuse? Not necessarily. In Peter's situation, the test was that of the integrity of the insulation between the TNV circuit and the other circuits. So, if the "fused" trace did not bridge the insulation, then there should be no consideration that the trace was being used as a fuse. It is simply a failure, and a particular kind of failure -- open-circuit. Many, many fault-condition (abnormal) tests end up with an open circuit. We don't treat all component open-circuits as fuses. So, why should we treat an open trace as a fuse? It is unlikely that fusing of a trace will bridge a safety insulation. On the other hand, fusing of a transformer winding wire may be associated with enough heat to damage the solid safety insulation within the transformer! On the other hand, if the fusing of the trace should prevent an overheating situation (fire?), then the trace probably should be evaluated for its fusing action. So, one needs to understand the nature of the test in order to evaluate the results of the test to determine whether the opening of a trace is a fusing action as opposed to simply the end of a fault-condition test. Best wishes for the New Year, Rich - Richard Nute Product Safety Engineer Hewlett-Packard Company Product Regulations Group AiO Division Tel : +1 619 655 3329 16399 West Bernardo Drive FAX : +1 619 655 4979 San Diego, California 92127 e-mail: ri...@sdd.hp.com - - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: UL1950 Overvoltage Tests
Hi Peter: I hope you have simplified the certification house response... "However, opening of a trace during component abnormals would be considered an unacceptable result." Such a blanket judgement denies an engineering evaluation of both the purpose of the test and the results of the test. I said: "Many, many fault-condition (abnormal) tests end up with an open circuit. We don't treat all component open-circuits as fuses. So, why should we treat an open trace as a fuse?" When a semiconductor fails open as a result of an abnorml test, the "open" is usually due to the fusing of an internal bond wire. (Other semiconductor faults may precede the fusing of a bond wire.) Such a result is commonly considered acceptable. Yet, how does it differ from the opening of a board trace? Let's consider first the purpose of the test. Most "abnormal" tests are intended to ascertain whether a fire will result. Other abnormal tests are intended to ascertain the failure of insulation, usually be means of overheating. Typical failure criteria for an abnormal test for fire is whether or not ignition occurs. The opening of a trace is undoubtably due to heating (due to excessive current, I*I*R). If no fire results, then the constuction is accepatable. Except, the termination of the overheating event was by opening of the trace. We all know that there is a lot of variability as to the time-current fusing characteristics of a trace. So, we would need to conduct some further tests to ascertain that a fire will not occur with the worst-case trace (i.e., larger cross-sectional area). Consider replacing the trace with a wire of relatively large cross-section and repeating the test. Now, something else fails and the test is terminated. There is either a fire, or there is not. If there is no fire, then the fusing of the trace SHOULD be acceptable. The two tests have proved that no fire is possible. So, one needs to know the purpose of the test, and one needs to evaluate the test results in terms of the purpose of the test. It is irresponsible for a certification house to make such a categorical statement as to whether or not a particular failure (i.e., opening of a trace) is an unacceptable result. Best regards, Rich - Richard Nute Product Safety Engineer Hewlett-Packard Company Product Regulations Group AiO Division Tel : +1 619 655 3329 16399 West Bernardo Drive FAX : +1 619 655 4979 San Diego, California 92127 e-mail: ri...@sdd.hp.com - > From owner-emc-p...@majordomo.ieee.org Thu Jan 7 14:15:19 PST 1999 > Received: from hpsdlo.sdd.hp.com (hpsdlo-sw.sdd.hp.com [15.26.112.11]) by > hpsdlfsg.sdd.hp.com with ESMTP (8.7.6/8.7.3 TIS 5.0/sdd epg) id OAA08737 for > ; Thu, 7 Jan 1999 14:15:18 -0800 (PST) > Received: from ruebert.ieee.org (ruebert.ieee.org [199.172.136.3]) > by hpsdlo.sdd.hp.com (8.8.6 (PHNE_14041)/8.8.5tis+epg) with ESMTP id > OAA08054 > for ; Thu, 7 Jan 1999 14:15:14 -0800 (PST) > Received: by ruebert.ieee.org (8.8.8/8.8.8) > id QAA09924; Thu, 7 Jan 1999 16:18:12 -0500 (EST) > From: pe...@itl.co.il (Peter Merguerian) > To: dmck...@corp.auspex.com, Rich Nute > Date: Thu, 7 Jan 1999 23:12:35 +0200 > MIME-Version: 1.0 > Content-type: text/plain; charset=US-ASCII > Content-transfer-encoding: 7BIT > Subject: Re: UL1950 Overvoltage Tests > CC: t...@world.std.com, n...@world.std.com, > Priority: normal > In-reply-to: <199901060008.qaa04...@epgc478.sdd.hp.com> > References: <3.0.1.32.19990105141949.00946...@mailhost.auspex.com> from > "Douglas McKean" at Jan 5, 99 02:19:49 pm > X-mailer: Pegasus Mail for Win32 (v3.01b) > Message-ID: <19990107212451692.AAA313@peter> > Sender: owner-emc-p...@majordomo.ieee.org > Precedence: bulk > Reply-To: pe...@itl.co.il (Peter Merguerian) > X-Resent-To: Multiple Recipients > X-Listname: emc-pstc > X-Info: Help requests to emc-pstc-requ...@majordomo.ieee.org > X-Info: [Un]Subscribe requests to majord...@majordomo.ieee.org > X-Moderator-Address: emc-pstc-appro...@majordomo.ieee.org > > To Rich, Doug and All Members, > > I just got clarification from UL that opening of a trace during > Overvoltage Tests is OK as long as unit passes either the Leakage > and Dielectric Tests. However, opening of a trace during > component abnormals would be considered an unacceptable result. > > Thank you everyone for all the input. > > > Date sent: Tue, 5 Jan 1999 16:08:51 -0800 (PST) > From: Rich
RE: Re: Electric Strength After Abnormals
Posted on behalf of a colleague: The Electric Strength test conducted after abnormal testing in accordance with IEC 60950 may be performed at room temperature, after the EUT has cooled down. 5.3.8.2 says the test is to be conducted in accordance with 5.2.2. 5.2.2 does not say anything about temperature, so the default is to allow testing at room ambient. For those cases in which the electric strength test is to be conducted in a well-heated condition, 5.2.1 is referenced, which indeed states this. The choice of reference to 5.2.1 or 5.2.2 was the subject of much debate in TC74. I can assure they were not arbitrary. The logic? Failure of insulation after an abnormal test is more akin to failure of insulation on the production line. That is, some influence (energy force) caused catastrophic failure of insulation. Temperature is likely to play only a small role in determining the long term integrity of the insulation under these circumstances. >From a practical point of view, it would be very time consuming and costly to always perform the Electric Strength test immediately upon termination of a simulated fault test, especially when the test is terminated by the opening of a component. To test while still in a heated condition would require constant monitoring of testing during working hours and would not allow testing to be conducted unattended. As a result, TC74 felt the value of conducting the Electric Strength test with the equipment in a well-heated condition after a fault test does not justify the cost. Regards, The Unknown Standards Guy - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Magnetic field monitors
Hmmm. Let's see: Magnetic field strength is measured in: amperes/meter oerstads Magnetic flux density is measured in: tesla gauss As near as I can tell, there is no conversion from one to the other. This would imply they are separate phenomenon. I'm not in the EMC field, but I'm curious as to regulatory requirements and what "interferences" such emissions would cause. (I'm presuming both are regulated.) Best regards, Rich - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Electric Strength After Abnormals
Hi Peter: > After an Abnormal Test for UL1950/EN60950, should the Electric Strength be > done a) immediately after the Abnormal Test or b) after Abnormal Tesrt when > unit has cooled down to room temperature c) after Abnormal Test when unit > has cooled down to Normal Heating Temperature Levels. As I recall, the electric strength is performed immediately after the abnormal test. However, the time from the end of the abnormal test to the initiation of the electric strength test should not be critical to the results. If time is critical to the results, then the implication is that the electric strength of the insulation is somehow a function of temperature. I would not expect this to be the case for conventional organic insulating materials. Organic insulating materials decompose with heat. The long-chain carbon molecules are broken into shorter chain molecules and the carbon begins to predominate. They do not reconstitute as they cool. Hence, the change of color towards brown and black. Carbon, of course, is a conductor, and will cause a failure of the electric strength test. The failure voltage may be higher when the insulator is cold, but it should nevertheless fail the electric strength test. I believe there are some inorganic insulators used in sheathed heating elements whose electric strength may be a normal function of temperature. If this is the case, then damage to the insulator can only be assessed at room temperature. Best regards, Rich - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Copy of: GROUND COLOR CODE FOR CE MARK (EN60204-1)
Hi Chris: There are two kinds of circuits that may be connected to the equipment protective earth terminal: 1) Protective earthing circuits. 2) Functional earthing circuits. Protective earthing wiring must be colored green/yellow. Functional earthing wiring can be colored any other color. In some electronic products, functional earthing wiring is colored black (by convention). Protective earthing wire size must be at least equal to the power cord wire size (because it must carry the fault current provided by the power cord). In some cases, on the load side of an internal fuse, the wire size may be smaller. Functional earthing wire size may be any size. Both sets of circuits can be connected to the same terminal. However, if this is the case, then the protective earthing wiring must not be disturbed while servicing the funtional earthing wiring. Usually, this means double-nutting of the protective earthing connections, and then placing the functional earthing on top of the double-nuts, with its own nut. Best regards, Rich - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Cell Phone Hazards?
Hi Barry: Thanks for the URL. An even better paper at the FCC web site is: http://www.fcc.gov/oet/info/documents/bulletins/#56 OET Bulletin Number 56 (Fourth Edition August 1999) Questions and Answers about Biological Effects and Potential Hazards of Radiofrequency Electromagnetic Fields This is an informative bulletin written as a result of increasing interest and concern of the public with respect to this issue. The expanding use of radiofrequency technology has resulted in speculation concerning the alleged "electromagnetic pollution" of the environment and the potential dangers of exposure to non-ionizing radiation. This publication is designed to provide factual information to the public by answering some of the most commonly asked questions. It includes the latest information on FCC guidelines for human exposure to RF energy. This document includes a very good and comprehensive description, annotated, of the various health effects of RF energy, including the non-heating effects. It includes information on power output of cell phones and possible health effects. It appears to answer all of the questions brought up here in this discussion. Best regards, Rich - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: warning label overkill?
Hi Ralph: > In the interest of safety, why place the onus on the consumer when he/she > had nothing to do with the design? There are two possible reasons: 1. The manufacturer either doesn't want to fix the problem or he doesn't know how to fix the problem. 2. The manufacturer is covering himself against liability. Warnings may allow the manufacturer to avoid liability following an injury. Attached to this message is a response from a colleague who gives some background for the soft drink warning label. He says that both of these factors (reasons) were involved in the soft drink episode. Best regards, Rich - Richard Nute Product Safety Engineer Hewlett-Packard Company Product Regulations Group AiO Division Tel : +1 858 655 3329 16399 West Bernardo Drive FAX : +1 858 655 4979 San Diego, California 92127 e-mail: ri...@sdd.hp.com - ... Hi Rich, Do you not remember the lawsuit a few years ago (maybe you were in Spain)? A stocker managed to damage a bottle of soda and the cap flew off and hit him in the eye. I don't know whether it caused any serious injury or not, but it did engender a lawsuit. Two things happened as a result: (1) the warning quoted in this message became commonplace, and (2) the screw design on the top of the bottle was modified - there are now slots cut through the threads to relieve pressure as the cap loosens, so that it cannot become such a high-speed missile. I can imagine that different bottlers have taken different time scales to introduce the new bottle design, and to phase out the temporary warning. Regards, Ray Corson - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: AC Mains Color Coding
Hi Robert: > But what about permanently connected products? For the purposes of Article 400-22(c), the NEC does not distinguish between permanently-connected and plug-and-socket-connected appliances. The rule is: > Specifically, 400-22(c): > > "For jacketed cords furnished with > appliances, one conductor having its > insulation colored light blue..." So, if the cord is furnished with the appliance, then the neutral may employ a light blue insulation. Many industrial appliances are permanently connected by means of a jacketed cord that is permanently connected at the appliance end. My interpretation is that such a cord could have its neutral colored light blue. Best regards, Rich - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: AC Mains Color Coding
Hi Robert: > Yes certain UL standards have accepted the Lt Blue for the neutral. But > therein lies the conflict. The NEC states that the neutral (grounded > conductor) must be white or nat. Gray. Has there been an acceptance by the > NEC for the blue neutral?? Yes, the NEC does indeed accept blue for the neutral color for cords, but not for building wiring. See: Cords: NEC Articles 200(c), 400-22(c), 400-23. Buildings: NEC Articles 200-7, 210-5. Specifically, 400-22(c): "For jacketed cords furnished with appliances, one conductor having its insulation colored light blue..." (UL would not accept blue unless the NEC first accepted blue.) Best regards, Rich - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: AC Mains Color Coding
Hi Robert: Here's a table that should explain the use of single- phase mains wiring colors: ---+--CONDUCTOR---+ |-Europe---|---North America---| | L N PE | L N PE | ---|--|---| | | | Within a product | n/a n/aY-G | n/a n/a G-Y | | n/a n/aG-Y | n/a n/a Y-G | ---|--|---| | | | Cordage| Bro Blu Y | n/aW G | (connecting the| Bro BluY-G | n/aWG-Y | product to the | Bro BluG-Y | n/a BluG | building) | | n/a Blu G-Y | | | ((Blk) W G) | | | ((Bro) Blu G-Y)| ---|--|---| | | | Within a building | Bro Blu Y | (Blk) W G | | | (Blk) WG-Y | ---+--+ where: n/a = not applicable (no rule) Y = Yellow G = Green Y-G = Yellow with green stripe G-Y = Green with yellow stripe Bro = Brown Blu = Blue Blk = Black W = White ( ) = by convention, not by rule L = Live or Line N = Neutral PE= Protective Earth (grounding) References: Cords: NEC Articles 200(c), 400-22(c), 400-23. Buildings: NEC Articles 200-7, 210-5. Products: IEC 950, Sub-clause 2.5.5. Best regards, Rich - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: safety ground wire
Hi Darrell: > I have in the past worked on a UPS project where we provided double > insulation from all hazardous voltages to the operator interface, and a > three pronged line cord with the green wire ground bonded to the chassis. > In essence we had both types of protection which we thought was good. > However, we received some confilcting views on this, especially concerning > Europe. Some people said we could not have both. I do not remember the > reasoning why. Is there anything prohibiting simultaneous protection > schemes? We routinely use double-insulation in our grounded products. We do this because we KNOW that some of our products will be used without a ground. (Our ground wire is for EMC purposes, not for safety purposes.) It is almost impossible to build a grounded product (with an accessible secondary circuit) without using double- or reinforced insulation at a number of points within the product. If you use a detachable power cord and an IEC 320 appliance coupler, then you have reinforced insulation in the coupler. If you use an operator-accessible fuseholder, then you have reinforced insulation. If you use a plastic power switch, then you have reinforced insulation. Socket-outlets and wall switches are reinforced insulation. Within the product, primary and secondary wires are separated by supplemental air or solid insulation: the primary wire has the basic insulation and the secondary wire (if rated the same as the primary wire) has the supplmental insulation. (If not rated the same, then you are using air insulation for the supplmental insulation.) Between bare parts of primary circuits and bare parts of secondary circuits, you are using reinforced air insulation (a nonsense concept). The primary-secondary coils of switching-mode transformers are almost always separated by double or reinforced insulation. (A grounded barrier in a switching mode transformer reduces its performance.) The power supply printed wiring board necessarily uses air and solid reinforced insulation between primary and secondary. A true grounded product would have a solid metal grounded barrier between all of the primary and all of the secondary. This is hard to imagine. Examples of products that are grounded and do not use double or re-inforced insulation are a breaker panel, a metal conduit, a washing machine, a refrigerator, and similar construction that has a continuous grounded metal enclosure for ALL circuits. So, a combination of grounded and double-insulated construction is common, although often not recognized. The IEC forces the product into either the Class I (grounded) camp or the Class II (double-insulated) camp without recognizing or evaluating the Class II construction within the Class I product! The two schemes can and should be recognized as co-existing in the same product. Indeed, a Class I construction can be employed within a Class II product -- without grounding the product. (If you are interested, ask me how.) Neither is better than the other; they each provide equal protection against electric shock. Best regards, Rich - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: safety ground wire
Hi Ken: > Thank you for your comprehensive answer. I am a little surprised that after > all the discussion in this forum on specs relative to the width of the > yellow stripe on the green wire that there is no rule on how or if things > get a green wire in the first place! The choice of whether to design any particular product as double-insulated or grounded is the manufacturer's choice. The rules are: If your product is grounded, it shall meet these requirements... If your product is double-insulated, it shall meet these requirements... We, HP, make both double-insulated and grounded computer peripheral products. We waffle back and forth between the two constructions, and are not consistent in our choice. Our primary motivation is cost. Two-wire seems to be lower cost (one less wire, etc.). But, the EMC filter seems more difficult to design. Then, we are concerned with worldwide distribution. The same two-wire plug can be used in many more countries than the grounded plug (i.e., Denmark, Switzerland, Italy). So, there are fewer power cords to stock. But, we already stock all of the grounded power cords. Finally, there is customer convenience. Two-wire works everywhere, grounded only works in a grounded environment. Japan residences are 2-wire. Many European residences have both grounded and 2-wire outlets in various parts of the home. Many homes in North America still have 2-wire outlets. So, there seems to be some advantages to 2-wire. On the other hand, grounded is a very familiar construction, and is easy and straight-forward for both design and manufacturing. No rule. Manufacturer's choice, but biased by competition and "inertia" of the product line. Vacuum cleaners are 2-wire; washers are grounded. Best regards, Rich ps: Yes, we do get hung up on issues such as the width of the stripe on the grounding conductor because this is a RULE. The choice of using a grounding conductor is NOT a rule. The only rule is that the product must be either grounded or double-insulated. - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: safety ground wire
Hi Ken: > What determines whether equipment gets a green wire or not? TVs, toasters, > handheld hair dryers and just about anything for home use get two wire power > cords. Computers and other ITE get three wire cords. Is the distinction > commercial vs. residential (class A vs. Class B)? It doesn't seem purely > safety related, since a metal toaster would appear to be more prone to > dangerous electrical faults than a doubly-isolated all plastic handheld hair > dryer. What is the rule here? There is no rule. Two-wire (double-insulated) products are equally safe as three-wire (grounded) products. Regardless whether metal-enclosed or plastic-enclosed. The safety difference is that a double-insulated product is independent of the building installation, while the grounded product is dependent on the building installation (i.e, the building wiring must have grounded outlets throughout). In modern buildings, all outlets are grounded, so the safety difference is moot. Whether the product is double-insulated or grounded is a matter of the "inertia" of the industry or of the manufacturer. Home appliances, including TVs, existed before the advent of grounding. Hence they were 2-wire, and they remain 2-wire. Inertia. Based on a straw poll of my fellow employees, about one-third live in houses with 2-wire outlets. So, it is prudent to build double-insulated products for residential use. On the other hand, PCs were derived from large, commercial computers that had 3-wire cords. So, the inertia was grounded products. Most PCs and computer peripherals are grounded. Portable electric tools originally were 2-wire, metal encased. Then, with the advent of grounding, they became 3-wire, metal encased. But, grounding was not reliable in construction sites, and many were injured by electric shock. So, the portable tools industry changed to 2-wire, plastic-encased tools. Another factor is EMC compliance. For higher current products with input rectifiers and energy storage capacitors, EMC filtering is easier with a ground wire. Toasters, hair dryers and similar heating appliances need no EMC filtering. >From my point of view, the choice of double-insulated versus grounding is one of customer convenience. A 2-wire product can be used anywhere; a grounded product can be used only with a grounded outlet. There is a minor safety issue with 2-wire electronic products with EMC filters. Under some circumstances, the leakage current, although well under the allowable limits, can be detected by the body, and can be rather annoying. (Under the correct circumstances, the body can detect leakage currents -- through the skin -- in the 40 microampere range; I've done it!) Best regards, Rich - Richard Nute Product Safety Engineer Hewlett-Packard Company Product Regulations Group AiO Division Tel : +1 858 655 3329 16399 West Bernardo Drive FAX : +1 858 655 4979 San Diego, California 92127 e-mail: ri...@sdd.hp.com - - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Cell Phone Hazards?
For another view of cell phones and cancer, see: http://www.mcw.edu/gcrc/cop/cell-phone-health-FAQ/toc.html Click on: Moulder et al: Cell Phones and Cancer: What Is the Evidence for a Connection? Radiation Research 151(5):513-531, May 1999. Best regards, Rich - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Article to UL
Hi Barry: > Chaz, Why do they call UL a non-profit organization? UL, as a corporation, is chartered as a "not-for-profit" organization. This means that it cannot distribute retained earnings to the owners. Instead, it uses retained earnings to add to endowment funds for financing future activities. Indeed, there is a limit as to the magnitude of retained earnings. One year, back in the '70's, UL rebated funds to all of its clients proportional to their UL expenditure because the UL retained earnings exceeded the legal amount! Apparently, UL has some sort of tax advantage as a result of its not-for-profit status. UL does not have a board of directors, but has a Board of Trustees. I like to draw an analogy with a church. The question is: Who are the "owners?" The answer is: The Board of Trustees. The Board decides the acquisition, use, and disposition of the assets of the Corporation. Insofar as its daily operations, UL is managed just as is a profit-making enterprise. Best regards, Rich - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: UL in Washington Post
Hello from San Diego: Many thanks to Sean for posting the URL for the Washington Post article on UL. While I am notorious as a "UL-basher," I think the focus of this article is misplaced. This article presumes that UL puts the safety into products. Unfortunately, many manufacturers also believe that UL puts the safety into their products. Manufacturers, not UL, are responsible for the safety of their products. UL is a certifier. UL certifies that the product complies with the requirements published in a standard. The requirements contained within the standard for the most part specify protections (i.e., safeguards) against specific (and known) hazardous conditions or situations. The criticisms leveled against UL represent short- comings in the standards. Specifically, the criticisms are that of hazardous conditions or situations NOT COVERED in the standards. The article implies that UL is expected to know, IN ADVANCE OF ANY SAFETY INCIDENT, of any and all hazardous conditions and situations AND specify safeguards against those hazardous conditions and situations. This is a very difficult and almost impossible task, especially for UL, since UL does not have good means of feedback on safety problems. One wag said, "Safety standards are the inversion of bad experiences." This implies that we can't know of safety problems until an injury or fire is incurred. For many safety issues, this is indeed the case. But, the manufacturer almost always gets feedback on safety problems with his products. So, the question is: Why don't manufacturers respond with fixes to their product and with input to the standards so as to prevent recurrence of the safety problem? (The article cites several instances of safety problems where inadequate, late, or no action was taken to address the safety problem.) I suggest that the are several answers. One is that managers do no like to admit that their product may have failed to provide the needed protection. The article describes how we tend to blame the environment or the failure to follow instructions, etc., etc. Another is that product change is expensive, especially when the competitor may not need to make the same change. Within a standards committee, a manufacturer does not like to admit that he has a safety problem that needs to be addressed by the standard. Yet another is that investigations into safety incidents are often insufficient or inadequate as to truly identify root cause. So, I think the focus on UL is misplaced. We, the manufacturers, should be the focus of the article. Consider the article as directed to your safety function! Best regards, and for my USA colleagues, west wishes for the Thanksgiving Holiday, Rich - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Floating Circuits - Protection Against Electric Shock
The original article was published in the Product Safety Newsletter, which is now web-based. See: http://www.ewh.ieee.org/soc/emcs/pstc/ http://www.ewh.ieee.org/soc/emcs/pstc/tech-spk.htm Now that the PSN is on the web, I find I can use more detailed and colored illustrations. All of my safety articles are originally published in the Product Safety Newsletter, not in commercial magazines. 'Conformity' magazine reproduced the article with my permission. I usually give permission to use my copyrighted material in other venues AFTER it is published in the PSN. This particular article is also published on at least one other web site. If the demand is not too great, I can provide .pdf copies via e-mail. Send me private e-mail if you are interested. My big concern is that, since I don't get any money for my articles (they're donated to the PSN), I don't want others to make money from my donation to the PSN. Occasionally, I do grant permission to commercial publication such as 'Conformity,' but I demand that credit and reference go to the PSN. My long-term objective is to develop product safety as an engineering discipline, and downgrade product safety as conformity and certification to a standard. I want product safety engineers to think about exactly how the various requirements provide protection, if any. Hence, it is important to show the current pathway for electric shock, and how insulation provides protection against electric shock. If you compare my article to the requirements in IEC 60950, you will find that the IEC 60950 requirements are excessive. Best regards, Rich - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Railway Crossing Gate
> Will a child hold on to the gate as it opens in order to= > "ride" it and if so what prevents injury. As I child, I was a paper boy. The papers were delivered to our town by train. We picked up our route package at the train station as it was thrown from the baggage car and then we delivered the papers. Normally, we were at the train station before the train arrived. I remember one occasion when the Greyhound bus that crosses the tracks at the station had stopped a foot or so beyond the crossing gate (but well away from the tracks). The gate came down and struck the bus on its roof, and then rested there. Small dent in the metal roof. This was exciting stuff for us paper boys! We found that one paper boy, approximate age 10, pushing down on the counterweights, could easily lift the gate above the roof of the bus. I'm not sure if one of us could ride the gate on its upswing. We'd never do it because we'd have to do it in front of 4 lanes of stopped traffic. I'm not at all sure that the gate would lift a 10-year-old. Anyway, it never crossed our minds. But, I do know that once the gate was up, a 10-year-old boy could not force the gate down by pushing on the counterweights. It was clearly locked in the upright position. Best regards, Rich - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: WEEE Directive
Hi Richard: >Are there currently any > alternative wire and cable constructions that comply with UL and NEC flame > requirements without the use of halogenated flame retardants? I believe PVCs are "naturally" flame-retardant materials i.e., have no flame retardants added to them. Many commonly-used wire and cable insulations are PVC. Best regards, Rich - Richard Nute Product Safety Engineer Hewlett-Packard Company Product Regulations Group AiO Division Tel : +1 858 655 3329 16399 West Bernardo Drive FAX : +1 858 655 4979 San Diego, California 92127 e-mail: ri...@sdd.hp.com - - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Hot Surface. Hot air.
Hi Peter:
> Why don't you discuss the BOGSAT with Richard Pescatore, the Chairman of
> the WG7 Technical Committee; I believe he represents your company Hewlett
> Packard and the US ITE industry in the IEC Technical Committe for 950.
Richard Pescatore and I keep in touch. He knows my views
on BOGGSAT. He is doing what he can to minimize BOGGSAT,
but he must balance all the various issues facing WG7. Due
to these other issues, many requirements are, out of
necessity of the moment, driven by BOGGSAT. Unfortunately.
> You and others should be more involved in these meetings to understand how
> the requirements evolve. There is a lot of research involved. So before you
> mention the word "BOGSAT", I suggest to talk to Rich and to check how the
> requirement came about. OK?
My company already sends several people to these meetings.
We don't want to abuse or take advantage of our presence.
So, I don't attend.
Rich does provide me with draft copies of many, if not all,
of the proposals. I do comment on many of them. Rich and
I discuss many of the proposals. Rich and the other HP
folks represent my views at the meetings.
Overturning long-standing BOGGSAT requirements, even with
data, usually is not successful. On the other hand, new,
or major revisions to requirements, often are receptive to
basing the requirements on data.
I disagree that "There is a lot of research involved." I
have rarely seen committee members accept research
assignments to understand the issue and propose requirements
based on the research. (The folks who've written IEC 990
are an exception.)
The issue that triggered my BOGGSAT remark was that of hot
parts and the empirical analysis presented to this group
that the allowed metal temperatures are too high. Clearly,
no committee member has researched these requirements, or
has applied his engineering training in thermodynamics to
recognize that temperature alone cannot result in an injury.
The requirement was generated by BOGGSAT.
I demand that product safety engineers (and safety standards
committee members) apply their engineering training to the
job of making products safe. For the most part, product
safety engineering is not a high-powered engineering
("rocket science") discipline, but it does require applying
engineering principles to the requirements. When
engineering principles are ignored, I lose my patience.
Best regards,
Rich
ps: Art Michael pointed out that the acronym BOGSAT should
be BOGGSAT.
(Bunch Of Guys and Gals Sitting Around Talking.)
> From pmerguer...@itl.co.il Fri Oct 8 01:39:46 PDT 1999
> Received: from hpsdlo.sdd.hp.com (hpsdlo-sw.sdd.hp.com [15.80.36.40]) by
> hpsdlfsg.sdd.hp.com with ESMTP (8.7.6/8.7.3 TIS 5.0/sdd epg) id BAA03026 for
> ; Fri, 8 Oct 1999 01:39:46 -0700 (PDT)
> Received: from nt-server.itl.co.il ([209.88.190.98] (may be forged))
> by hpsdlo.sdd.hp.com (8.8.6 (PHNE_14041)/8.8.5btis+epg) with ESMTP id
> BAA28458
> for ; Fri, 8 Oct 1999 01:39:39 -0700 (PDT)
> Received: from peter ([194.132.55.103]) by nt-server.itl.co.il
> (Netscape Mail Server v2.02) with SMTP id AAA88;
> Fri, 8 Oct 1999 10:48:58 +0200
> Message-Id: <3.0.5.32.19991008103813.00798590@194.132.55.100>
> X-Sender: pmerguerian@194.132.55.100
> X-Mailer: QUALCOMM Windows Eudora Light Version 3.0.5 (32)
> Date: Fri, 08 Oct 1999 10:38:13 +0200
> To: Rich Nute , israel_yeshu...@stcl.scitex.com
> From: pmerguer...@itl.co.il (Peter Merguerian)
> Subject: Re: Hot Surface. Hot air.
> Cc: emc-p...@ieee.org
> In-Reply-To: <199910080042.raa18...@epgc478.sdd.hp.com>
> References:
>
> Mime-Version: 1.0
> Content-Type: text/plain; charset="us-ascii"
>
> Rich,
>
>
> You state: "Unfortunately, the authors of our various safety standards
> chose the BOGSAT* method of determining safety rather than doing research."
>
> Why don't you discuss the BOGSAT with Richard Pescatore, the Chairman of
> the WG7 Technical Committee; I believe he represents your company Hewlett
> Packard and the US ITE industry in the IEC Technical Committe for 950.
>
> You and others should be more involved in these meetings to understand how
> the requirements evolve. There is a lot of research involved. So before you
> mention the word "BOGSAT", I suggest to talk to Rich and to check how the
> requirement came about. OK?
>
> Peter
>
>
>
>
>
>
>
>
>
>
>
>
>
> At 17:42 07/10/99 -0700, Rich Nute wrote:
> >
> >
> >
> >Hello Israel:
> >
> >
> >Unfortunately, safety standards o
Re: Hot Surface. Hot air.
Hello Israel: Unfortunately, safety standards only address one of the critical parameters, temperature, when specifying requirements for protection against a burn injury. You are absolutely correct that a metal surface with a temperature exceeding 50 C is capable of producing a burn injury. There are four parameters that must be taken into account: 1. temperature 2. thermal conductivity of the material 3. thermal capacity of the material 4 duration of contact One can easily touch aluminum foil at 100 C and higher for an indefinite duration because its thermal capacity is very low. One can easily touch plastic at 100 C for an indefinite duration because its thermal conductivity is very low. One cannot touch a 25 mm or larger cube of aluminum at 50 C for longer than 10 seconds without burning the skin because its thermal conductivity and thermal capacity are high. There is no regulatory source that addresses all four parameters. Instead, you must consider your training in the field of thermodynamics, and you must consider the literature where the burn parameters of human skin are published. If you look, you will find published data relating skin temperature and duration to pain and to skin burns.** Unfortunately, the authors of our various safety standards chose the BOGSAT* method of determining safety rather than doing research. The requirements you mentioned are indeed inadequate. But, you have already determined that. So, using your training as an engineer, you can make your product safe for both the hot surfaces and the hot air in spite of the standard. Best regards, Rich - Richard Nute Product Safety Engineer Hewlett-Packard Company Product Regulations Group AiO Division Tel : +1 858 655 3329 16399 West Bernardo Drive FAX : +1 858 655 4979 San Diego, California 92127 e-mail: ri...@sdd.hp.com - * BOGSAT = Bunch Of Guys Sitting Around Talking. ** Stoll, Alice M., "Thermal Properties of Human Skin related to Nondestructive Measurement of Epidermal Thickness," Journal of Investigative Dermatology, September, 1977, pp. 328-332. - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: EN60950 - conduit entry dimensions
Hi Jim: > Aren't there any permanently connected ITE equipment mfr's on this > forum?! What do you provide in the way of knockouts or ...??? I don't have any first-hand experience... but... On good authority, a major mainframe manufacturer uses cord-and-plug connection for EVERYTHING! The plug is one from the IEC 309 series of industrial plugs. No permanent connections. Why not use an IEC 309 plug and appropriate cord? (I believe these plugs and sockets are readily available from USA industrial plug manufacturers.) Best regards, Rich - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
EMC position at HP
Hewlett Packard's Network Server Division in Cupertino, CA is looking for a Senior EMC Engineer to work on EMC requirements for electrical and mechanical development. This position is an Architect position looking at future product designs. The person will establish processes to create product line consistency across all existing and future platforms. This position requires detailed knowledge of EMC design techniques and EMC testing procedures. Please contact Erin McLaughlin at 408-873-5974 or email at erin_mclaugh...@hp.com - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Screen Dimensions - Fire Enclosures
Hi John: > the largest size listed in the table is 1.00mm minimum metal thickness, > 2.00mm maxhole dia., and 3.00mm minimum center-center hole spacing. If my > metal thickness was greater (1.27mm), and my center-center hole spacing was > 4.75mm, could I not go to a larger hole (3.175 - .125")? The basic requirement is found in Annex A.5, Hot Flaming Oil Test. Table 15 lists a set of hole diameters and center-to-center distances between holes as a function of metal thickness. These combinations are such that hot flaming oil will extinguish when passing through the holes. The oil does not burn at room temperature. It must be heated before it will ignite. The burning oil is poured onto the perferated sheet metal. The combination of hole diameter, center-to-center spacing, and metal thickness combine to cool the oil and exclude oxygen when the oil passes through the oil such that the oil that passes through the holes ceases to flame. The extinguishing process is twofold: 1) The bottom surface of the oil film is cooled by the available metal surface. The top surface of the oil is heated by the flames and continues to burn. 2) As the oil passes through the hole, the hole actually fills with oil such that oxygen does not pass through the hole and thereby does not support combustion to the cooled oil that passes through holes. So, the thicker the metal, the more cooling. The larger the hole, the more likely the flame will follow the oil through the hole. 2 mm is about the largest diameter hole that will not allow the flame to pass through. So, you will need to rely on cooling alone. The hole-to-hole spacing and the metal thickness will have to cool the oil below ignition temperature as it falls through the hole. Not likely, in my opinion. The only way to know for sure is to perform the test. The test is easily performed in a fume hood with tools readily available from a grocery store or kitchen specialty shop. A metal ladle with a metal handle. For some ladles, you will need to bend the handle to make it do this job. I use the largest aluminum foil roasting pan to catch the oil. I use a small aluminum cake pan (inverted) or equivalent to place the cheesecloth on. The height of the ladle above the specimen is critical and must be maintained constant. I use a rest for the ladle handle positioned so that the ladle is at the correct height. The rate of pour is also critical. You will need to practice your timing of the pour to get the rate correct. You'll need someone to help by giving you a countdown as you pour (you can't watch a clock and pour at the same time!). I use putty to make a dam to prevent the oil from going over the edge of the specimen. Put the dam at the edge of the specimen so the oil spreads over the specimen, and does not concentrate at the holes. The oil is standard diesel or household heating oil. You may need a fire extinguisher to extinguish the fire in the roasting pan. The test is flaky, and not super-repeatable. The pass criterion is two passes in succession. (All non-passes are treated as practice tests.) It takes good technique (constant pour rate, and constant height) to get a pass. Best regards, Rich - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Fwd:Re: EN 60 950 and Denmark-> conv. class I into class (fwd)
Hi Peter: >Well, can you share how your compliant products (ie double insulated to earth >Class I products) comply at the transistor/earthed heat sink interface? Do you >have at least two layers of insulation where each layer meets the reinforced >insulation dielectric strength test requirements? I do not think so? In the power supplies I have been associated with, the heat sink is connected to the negative dc rail, not to ground. Consequently, there is no need for double insulation between the switching transistor and the heat sink. >How is the weather in San Diego? The past few days have been hot, with temperatures yesterday at the coast of 80 F, and in our back yard of 95 F. So, yesterday was the hottest day of the year in San Diego. Dry heat, so it was not too uncomfortable -- not as bad as a few weeks ago when we had 85 F and high humidity. Best regards, Rich - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: EN 60 950 and Denmark-> conv. class I into class II
Hello from San Diego: > One thing that might be a problem is if the heat sink of the primary > switching > transistor is grounded. > > Then it might be difficult to reinforced isolate the primary switching > transistor as changing the isolation material will also influence the heat > conducting properties and thus the life span of the transistor. Agreed. However, in the power supplies that I've worked with recently (50 W max input), the heat sink is either floating or connected to the negative DC rail. I believe the negative DC rail is better for EMC than floating, and may be better than ground. Perhaps our EMC colleagues could comment on the least EMC connection for switching transistor heat sinks? Best regards, Rich - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: IEC 127 fuse
Hi Rick: > Do any of you know where I can find a 1 1/4" fuse, that meets IEC 127 (EN > 60127)? As I recall, IEC 127 does not include the 1-1/4 inch dimensions, and therefore there are no IEC 127 fuses in the 1-1/4 inch dimensions. Indeed, this would be dangerous as the methods of rating fuses is different between IEC 127 and UL/CSA standards. Consequently, a 3-amp IEC 127 rated fuse cannot directly replace a 3-amp UL/CSA rated fuse. At one time, several fuseholder manufacturers made fuse- holders that would accept either the 5 x 20 mm fuse or the 1-1/4 inch fuse. This would be one way of solving your problem (although it does require changing the fuseholder). Best regards, Rich - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Re: EN 60 950 and Denmark
Hi Peter: > This is the exact deviation which I was referring to. One of my > clients states that a distributor wishes the product to be safe for > those establishments where earthing cannot be relied upon. Does > this mean to provide double or reinforced insulation from hazardous > live parts to earth? This may be a pain killer if the power supply is > Apporved for Class I. Not necessarily. Today's designs of SMPS are typically double or reinforced insulated. Even if certified as Class I, you have the option of evaluating it for double- or reinforced-insulation and declaring it as complying with double- or reinforced-insulation for use in Denmark (and other Nordic countries where grounded outlets may not be present in the electrical installation). There are two insulations that must be considered: primary-to-secondary primary-to-ground 1. Primary-to-secondary. In a typical SMPS, there are three such insulations that must be considered: transformer opto-isolator PWB spacings Typical SMPS transformers are double-insulated. It is very inefficient for a SMPS transformer to employ a grounded shield. If the certifier did a good job, he will have ascertained that the solid insulation, the through-air insulation, and the surface insulations meet the respective double-insulation requirements. In my experience, most SMPS transformers do meet these requirements. Opto-isolators are almost always rated as double- or reinforced-insulation. Most PWB spacings are those for double-insulation. If not, the secondary circuit and conductors must be grounded as if they were protective conductors. So, I believe you will find that most PWB spacings are sufficient for double-insulation. 2. Primary-to-ground. In a typical SMPS, there are two insulations that must be considered: PWB assembly and the metal chassis PWB spacings across Y capacitors and similar spacings Here is where you are likely to find spacings only sufficient for Class I. Most power supply vendors will likely balk if you should require Class II construction between the circuits and ground. But, you can easily get around MOST of the spacings by interposing a solid insulating sheet between the circuits and the grounded parts (e.g., chassis). You can get around the Y capacitor spacings by asking for double-insulated spacings on the PWB conductors. Its really not too difficult. Its really easy if you spec your power supply as double-insulated primary-to-ground and primary- to-secondary. Almost zero cost. By the way, we find that the weakest insulation in such designs is the Y-cap lead spacing on the PWB. We experience arcs in the range of 4-5 kV, well above the required 3 kV! We do this on all of our products. We KNOW our products will be used in situations without ground. So, we require our power supply vendors to provide double-insulation as well as grounding. Best regards, Rich - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: LCD Displays
Hi John: > Rich, you said below "Assuming you are using IEC 60950, a fire > enclosure is required for any circuit exceeding the limits of ELV, > independent of available current or power." > > Why did you mention "exceeding the limits of ELV" ?Surely specific > components require a fire enclosure, regardless of voltage ? ALL components require a fire enclosure. However, IEC 60950 has one alternative and one exception to "ALL." 1. Base requirement: Use of flame-retardant materials within a unit, AND Use of a fire enclosure. 2. Alternative base requirement: Use of extensive fault testing to prove a fire cannot escape from the unit. No need for a fire enclosure 3. Exception to fire enclosure (for components): Specified wire insulations; Motors that comply with Annex B; Components supplied by a Limited Power Source provided: -components are mounted on V-1 or better material; -specified wire insulations; Components in a 15 VA TNV circuit. No need for a fire enclosure for these components. A fire enclosure is required for all other components. (For example, a power supply would require a fire enclosure, but the low-voltage secondary circuits would not require a fire enclosure. This is a fairly common construction for low-power products, and for products where the power can be divided into low-power circuits.) There are THREE sets of criteria for a Limited Power Source: 1. Open-circuit voltage. 2. Short-circuit current. 3. Maximum VA. If a low-power inverter is supplied by a Limited Power Source, but the inverter increases the voltage to a value exceeding the open-circuit voltage criteria, then the inverter output, according to the Limited Power Source criteria, is not Limited Power and therefore requires a fire enclosure. By definition, any voltage exceeding the VOLTAGE LIMITS of a Limited Power Source (i.e., exceeding the limits of ELV) does not meet the criteria of a Limited Power Source and therefore requires a fire enclosure. Because this is contrary to the principle of the conservation of energy, and because power represents the heating energy of electric energy, some certification houses consider such circuits and the components in them to also be supplied from a Limited Power Source. Best regards, Rich - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: LCD Displays
Hi Duncan: > I have a product that has an LCD display with an Inverter that operates at > 100Khz 2KV and I believe is capable of supplying 6.5mA The question is does > it > require a fire enclosure? Assuming you are using IEC 60950, a fire enclosure is required for any circuit exceeding the limits of ELV, independent of available current or power. However, you MAY be able to invoke other requirements to avoid a fire enclosure. Here are some of the "outs:" Sub-clause 4.4.5.2, third dashed paragraph: Some interpretations of allow that once a limited power source has been achieved, ALL circuits down- stream from that limited power source are treated as limited power even if the voltage is stepped up above the limits of limited power. Sub-clause 4.4.1, method 2. This allows fault testing in lieu of a fire enclosure. Most low-power, high voltage inverters are rather simple circuits; extensive fault testing only involves a few components, so such testing is feasible and likely to result in acceptable results. > If it does what are the requirements for the flamability of the screen and > any > plastic protective covers fitted to it. A fire enclosure requires that the plastic materials be rated V-1 or better. Note that the fire enclosure need not be the overall product enclosure (e.g., screen), but can be an inner part designated as the fire enclosure for the inverter circuit. Best regards, Rich - Richard Nute Product Safety Engineer Hewlett-Packard Company Product Regulations Group AiO Division Tel : +1 858 655 3329 16399 West Bernardo Drive FAX : +1 858 655 4979 San Diego, California 92127 e-mail: ri...@sdd.hp.com - - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Bonding Meter
Hi Derek: > can anyone recommend a meter for making resistance measurements as low > as 1 milliohm? Check out the Hypatia Model 309 high-current-sourcing milliohmmeter. http://www.HypatiaInc.com Hypatia Inc. 15270 SW Holly Hill Road Hillsboro, OR 97123-9074 1-800-Hypatia (1-800-497-2842) Email:supp...@hypatiainc.com Note that Hypatia says that connections to the EUT will have 1-2 milliohms resistance in themselves. To measure 1 milliohm, you will need to use Kelvin probes. Best regards, Rich - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Y Capacitors on 480VAC input power suppply
Hi Dan: According to both IEC 384 and UL 1414, Y capacitors are rated up to 250 V rms, not higher. However, RIFA offers ac capacitors in their Y capacitor catalog pages rated up to 440 V and 500 V rms (without certifications). If you were to use one of these in a certified product, then you would have to engage the certifier to perform testing in place. I suppose you can put to Y caps in series. Note that the voltage divides inversely proportional to the capacitance. According to the RIFA catalog, Y caps are 20% devices. So, the voltage divider worst case would be 40% from the half- way point, where one capacitor would have 240 V + 40% of 480 across it, 432 V. Not good for reliability, especially for a safety component. I suggest you talk with the various Y cap manufacturers to find a suitable set of caps. Best regards, Rich - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Regulatory Opening at HP in Richardson, TX
Hewlett-Packard's High Performance Systems Lab has an opening for a regulatory engineer with experience in product safety. HPSL is located in Richardson, Texas (20 minutes north of Dallas). Our product line is high-end servers (V-Class, SuperDome). For more information contact: Dean Sablotny, HPSL staffing, +1 (972) 497-4894 Cecil Clayton, HPSL Product Regulations Manager, +1 (972) 497-4125 Posted by Richard Nute, HP San Diego. - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: help (plastics marking)
Hi Kyle: > I presently use a system of lot marking codes with a simple one-page > document that is shipped with each batch of parts from the vendor. The > document has the name of the vendor's QA person in signature and the > relevant lot numbers for each shipment from the factory and the exact > plastic material name and/or number with the UL 94xxx flame rating. All I This is also what you get if the fabricator subscribes to the UL fabricator's program and you request that your plastic parts be provided under the UL program! We let UL handle all of this for us through its fabricators program! > Many times a plastic part is used as a subassembly into a finished part. > The problem with this system is that tracing back a part number for a > finished part may not lead one into the subassembly part(s) so a disconnect > will occur making it difficult and time consuming to trace some parts to the > source unless you maintain a listing of parent part numbers and drawings for > inclusion to finished assemblies. This also means you must keep the list > current as engineering/manufacturing changes. UL has a new program, the Sub-assemblers program, which addresses this. No problem if the sub-assembler is a part of the UL program! > I have wanted to switch to a system similar to what Pryor uses, but with > dozens of individual parts, this will easily become an arduous task for me > and I'm not sure if it is acceptable anyway. If I'm gonna go to all that If you use the UL fabricators and sub-assembly programs, all of this is done for you by the fabricator and sub- assemblor. Marking of parts and sub-assemblies has many options under the UL programs: molded-in markings, separate certification sheets, box labels, individual part labels, almost anything you want. We leave it up to the fabricator/sub-assemblor by simply stating the certification is marked according to the UL standard (i.e., UL 746D). Best regards, Rich - Richard Nute Product Safety Engineer Hewlett-Packard Company Product Regulations Group AiO Division Tel : +1 858 655 3329 16399 West Bernardo Drive FAX : +1 858 655 4979 San Diego, California 92127 e-mail: ri...@sdd.hp.com - - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Plastics traceability...
Hi John: > My question: we have a UL mark on a box we build. One of the requirements > that the auditors check is flammability of materials. 2 parts give us > trouble - a molded bezel and a plex screen. Both are materials purchased > elsewhere by our fabricators. UL says either assemble a 'paper trail' that > shows continuous control of the materials, or use a 'recognized > fabricator' (read buck$) to make our parts. Neither fab. house is > recognized or wants to be. UL is VERY evasive about the required > documents for the 'trail'. Any one have this experience - and succeed? Ahh, yes. The famous UL "paper trail" syndrome. 1. The 'paper trail.' How do YOU know that the molded part is molded from the resin you specified for the part? Do YOU know how the fabricator tracks the resin from purchasing to the finished part? How are YOU satisfied that your fabricator is molding the part from the resin spec'd on your part drawing? Most of us (regardless of UL) require some sort of documentation accompanying the molded parts. At the very least, in order to accept the parts from the fabricator, the parts must have some sort of fabricator identification, order reference, and part identification (usually our part number). This is provided by the fabricator either pasted to the carton, or a shipping document, or a paper inside the shipping carton. Officially, the resin is a UL-Recognized Component. At your factory, the UL inspector must be able to identify the molded part as being molded from the UL- Recognized resin as specified in your end-product UL FUS Procedure. Your contract with UL obligates you to provide such identification. You're lucky. Your UL guy will allow almost any paper trail that includes the resin identification. So, all you need to do is to ask your fabricators to add the resin identification to the part identification document. We've done this, and it works. But, its iffy. The next UL inspector may be more strict and shut you down because you don't have official UL traceability. You COULD take the UL guy to the fabricator to verify that the fabricator is using the correct material when he molds your parts. Now THIS is spendy! 2. UL fabricators. There are lots of UL fabricators throughout the world. When I worked in Spain, we had no trouble finding and using Spanish UL fabricators. Once in a while, you will find a fabricator is not a UL fabricator. My policy has been that we need the fabricator to be a UL fabricator for traceability and control of the molding compound. We'll continue buying parts from him if he shows due diligence in obtaining qualification under the UL program. Never have we had a refusal. If the fabricator requires us to pay for the UL qualification, we say "yes," but also we say that we own the qualification, and he can't sell UL parts to anyone else. The fabricator doesn't take us up on our offer. Any fabricator who refuses to join the UL fabricators program won't enjoy good growth in his business. Too many of us require our fabricators to be UL. We won't do business with him since his competition offers UL. Being in the UL fabricators program levels the playing field for fabricators. Its a standard for being a fabricator. 3. Buck$. Not true. The person or organization who told you this was trying to get you off his case for applying for UL fabricator. A UL fabricator provides competitively priced products. Not an issue. As a general rule, UL simply documents the fabricator's process by which he tracks the resins from purchasing to the finished part. Then, the fabricator can use his UL code to identify that the parts have the traceability. If the fabricator's documentation is found by UL to be deficient, you should think twice about using that fabricator. It means he doesn't have adequate inventory control to guarantee that the part will be molded from the correct material. The cost of the UL investigation for a UL Fabricator is less than the cost of a full UL end-product investigation. FUS costs are the same as you experience for your products. No big deal. 4. Another way out. You can set up your FUS so that the plastic material is tested for the parameter required by the end-product standard during each FUS inspection. In most cases, the parameter is flame-rating. You can set up a lab to do the flame test each time the UL inspector shows up. You take a sample of each part from the production-line and perform the flame test. Easy. But UL will send an engineer to qualify your lab. Or, you can arrange for UL to perform the test at their labs. The UL guy selects a part from your production-
Re: UL legal requirement
Hi Jeff: > I am trying to find a basic document from UL and or CSA regarding the legal > requirement of > UL or CSA listing. I am thinking along the same lines as the European LVD. > Can anyone > offer insight as to whether this documentation exists? UL and CSA are private organizations. To my knowledge, neither has published any document describing how their respective certifications are required by Federal, State, County, and City laws. I believe that both feel that such a publication would be out of place and rather presumptive. How the various laws invoke third-party certification has been rather completely discussed in this forum from August 16 to August 19. See: http://www.rcic.com/ Click on: Virtual Conference Hall Click on: Browse Recent EMC-PSTC Threads Click on: Next 25 until you get to August 19. Then, click on: U.S. National Product Safety "Laws" (18) > The real question is: Is there a legal requirement to obtain UL or CSA > listing on a product > that operates at a low voltage (below 50VAC or 75VDC), does not have a > circuit that would > be classed as a TNV circuit, does not operate in hazardous explosive > environments, and > does not consume a high amount of power? The product is also not connected > to the mains > supply, it is specified to require power from a safety listed supply. The answer to this question must be determined from the NEC and from OSHA regulations. The NEC has regulations for low-voltage wiring installations (Article 625). So, if the product involves low-voltage building wiring, then it must be certified by UL or other acceptable certification. Since stand-alone (i.e., not a part of the building installation) low-voltage products are not addressed, then the NEC does not apply to such products. Consequently, under the NEC, flashlights and similar battery- operated products are not required to be certified. Furthermore, low-voltage products provided with an external power supply (adapter) need not be certified since the product is not part of the building installation. I was unable to find anything under OSHA rules that implies exemption of low-voltage products. Best regards, Rich - Richard Nute Product Safety Engineer Hewlett-Packard Company Product Regulations Group AiO Division Tel : +1 858 655 3329 16399 West Bernardo Drive FAX : +1 858 655 4979 San Diego, California 92127 e-mail: ri...@sdd.hp.com - - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: FW: Double pole fusing
Hi Alan: > We have recently had an EN60950 safety report from a local consultant on a > piece of IT equip we designed which commented that a fuse may be required > on both the live and neutral of the mains input for certain countries in > Europe. EN 60950, Sub-clause 2.7.1 states: "Protection in PRIMARY CIRCUITS against overcurrents, short circuits and earth faults shall be provided, either as an integral part of the equipment or as a part of the building installation, subject to the following, a), b), c), and d): . . . . "d) If reliance is placed on protection in the building installation, the installation instructions shall comply with 1.7.11, except that for PLUGGABLE EQUIPMENT TYPW A the building installation shall be regarded as providing protection in accordance with the rating of the wall socket outlet and 1.7.11 does not apply." Consequently, the product may rely on the building installation for earth faults and need not have double-pole fusing. This requirement applies to CENELEC countries. Other European countries MAY have different requirements. Hence, your local consultant was quite astute and responsible to point this out to you in his report. > Does everybody else fit a single pole fuse? I'd appreciate your comments. We use one fuse. We do not know of any European countries that double-pole fusing for single-phase equipment rated up to 16 A. Best regards, Rich - Richard Nute Product Safety Engineer Hewlett-Packard Company Product Regulations Group AiO Division Tel : +1 858 655 3329 16399 West Bernardo Drive FAX : +1 858 655 4979 San Diego, California 92127 e-mail: ri...@sdd.hp.com - - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Locate IEC 417 Markings
Hello from San Diego: > If you have the ability to print your own labels all of the IEC 417 symbols > are available on the web at > http://w3.hike.te.chiba-u.ac.jp/iec417/ver2.0/html/index.html. These are in > bitmap format. I have included the symbol for 5041 in this email in case you > can print your own. Note that this site bears a copyright. Further note that this site bears the following statement: "This document and following documents shall not be copied." Downloading and printing from this site may be contrary to the copyright. If you abuse the copyright, then the site may be shut down, and we may all lose the on-line reference. So, please abide by the copyright. (The site has been a valuable resource for us, but we don't download or copy the symbols.) Best regards, Rich - Richard Nute Product Safety Engineer Hewlett-Packard Company Product Regulations Group AiO Division Tel : +1 858 655 3329 16399 West Bernardo Drive FAX : +1 858 655 4979 San Diego, California 92127 e-mail: ri...@sdd.hp.com - - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Insulation between 12VDC and 230V - IEC65
Hi Pierre: Here is an ASCII block diagram of the construction the way I interpret your message: +---+ | | | dc-dc | 12 V dc --->| converter |---+ | | | | | | +---+ | +> 300 V dc +---+ | | | | | | | 230 V ac -->| rectifier |---+ | | | | +---+ (Note that this construction is the same as a UPS.) You mention that, when operating from 12 V dc, the only "insulation" between the 300 V dc and the 230 V ac mains plug is the diode rectifier. As a general rule, a semiconductor is not relied upon for insulation for the purposes of protection against electric shock (unless specifically rated as an insulator). When operating from 12 V dc, an electric shock hazard may exist BETWEEN THE POLES of the 230 V plug. When operating from 12 V dc, a leakage current shock hazard MAY exist from either pole of the 230 V plug to ground (DESPITE the isolation of the 300-V circuits from ground). The conventional safety approach to this construction is to use a transfer relay between the two 300-V sources: +---+ | | | dc-dc | 12 V dc --->| converter |---+ | | | | | | +---+ \ o--> 300 V dc +---+ / | | | | | | 230 V ac -->| rectifier |---+ | | | | +---+ This construction eliminates the need for safety isolation in the dc-dc converter. (Note that a similar problem, leakage current shock hazard, MAY exist from either pole of the 12 V dc plug to ground. In the absence of a transfer relay, a good safety approach would be to use a safety isolating transformer construction in the dc-dc converter as well as conventional pri-sec spacings and insulations.) Best regards from San Diego, Rich - Richard Nute Product Safety Engineer Hewlett-Packard Company Product Regulations Group AiO Division Tel : +1 858 655 3329 16399 West Bernardo Drive FAX : +1 858 655 4979 San Diego, California 92127 e-mail: ri...@sdd.hp.com - - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Suppression capacitors
Hi Nick: According to IEC 384-14 (1993): Class X and Y capacitors are ac capacitors. An ac capacitor is a capacitor "designed essentially for application with a power- frequency alternating voltage." Class X === A Class X capacitor is a capacitor where failure of the capacitor will not lead to electric shock. A Class X1 capacitor is rated up to 250 V rms and is suitable for Installation Category III (impulse-withstand is 4 kV) A Class X2 capacitor is rated up to 250 V rms and is suitable for Installation Category II (impulse-withstand is 2.5 kV). Class Y === A Class Y capacitor is a capacitor where failure of the capacitor could lead to conditions for electric shock. A Class Y1 capacitor is rated up to 250 V rms and is suitable for bridging double insulation or reinforced insulation (impulse- withstand is 8 kV). A Class Y2 capacitor is rated more than 150 V rms up to 250 V rms and is suitable for bridging basic insulation or supplementary insulation (impulse-withstand is 5 kV). I suggest you purchase a copy of IEC 384 as there are more details regarding application than can be posted here. Best regards, Rich - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
San Diego IEEE EMC/Safety September meeting.
IEEE Meeting Notice and News from The San Diego Chapter Wednesday, September 15, 1999. DESIGNING FOR SAFETY for the Year 2000 and Beyond. Charles M. Bayhi, P.E. About the Topic: The principles of product safety will be discussed as they relate specifically to EMC as outlined below: 1. Why Safety Certifications? 2. Worldwide Certification Marks 3. European Union and CE Marks 4. North American BiNational Standard for ITE Equipment - Another Y2K Problem 5. ITE, Telecom, Medical, Test and Measurement 6. Principals of Safety 7. Definitions 8. Markings and Instructions 9. Protection From Hazards 10. Wiring, Connection and Supply 11. Physical Requirements 12. Thermal and Electrical Connection to Telecom About the Speaker: Charlie Bayhi is a Product Safety Forensic and Consulting Engineer and has been involved in Product Safety on a worldwide basis for more than 30 years. He is President and Principal Consultant of CPSM Corporation, and provides product safety design guidance, development of Product Safety Programs, safety certification of products, forensic analysis of accidents and fires, and technical advisory for development of products and safety standards. Charlie is a Registered Professional Safety Engineer in the state of California, and a Subject Matter and a Technical Expert for the Board. He is a member of Underwriters Laboratories Industry Advisory Council, Vice President and Board Member of the Forensic Consultants Association Orange County, Vice President and Board Member of the Association of Professional Consultants, Member of the Institute of Electrical and Electronics Engineers (IEEE), Chairman of the Southern California Chapter, Technical Committee On Product Safety, of the IEEE, and a member of the IEEE Consultants Network. In addition to publishing numerous articles, Charlie has been a guest speaker at the Power Electronics Conference, and has made numerous Product Safety presentations, which include Fortune 500 companies such as AT&T Corporation, NCR Corporation, Canon Computers, Tektronix Corporation and Zero Corporation. Time/Place: TUV Product Service, 10040 Mesa Rim Road, San Diego, CA. (exit off I-15 West or 805 East at Mira Mesa Blvd., South on Flanders, right on Mesa Rim Road). Meal and Drinks available at 5:30 PM. (IEEE Members Free, Non-members $3.00) Please RSVP to Dave Bernardin at d.a.bernar...@ieee.org, or 619-546-3999. Reserve by Tuesday, 14 September 1999. The Business meeting will start at 6:00 PM. sharp, the Speaker will start at approximately 6:30 PM. - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Grounding Bond Test
Hi Kevin: > Interesting P.S. comment. Surely this can only be so if one is not dealing > with a CE country. I don't see how a test agency can waive the requirements > for meeting the LVD in Europe. If it is indeed as you say, then where does > it put those of us who have in house safety testing and self certify. I'm not sure that EN 50116 is a EU-adopted standard. If true, its use is at the discretion of the certification house. Or the manufacturer. The implication of your question is that ALL products bearing the CE (for safety) mark must be tested at 25 amps for 1 minute (or the lesser current). In either case, the 1-minute is onerous -- even prohibitive -- for high-volume production (i.e., where production approaches or exceeds 1/minute). We have a number of CB Certifications by non-Euro certification houses. None of these certification houses impose EN 50116. We DON'T perform a 1-minute test, nor do we perform a high-current test. Perhaps another of our subscribers can comment on the status of EN 50116 with respect to the EU. Best regards, Rich - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Grounding Bond Test
Hi Rick: > The obvious question I would have is... why couldn't you test at a higher > current for longer time meeting both requirements? For example 30A for two > minutes. I know the document indicates a maximum current, but does this make > sense? The original question appeared to me to ask why there are two different test currents. Of course, if you test at 30 amps for 2 minutes and pass, then you have also passed 25 amps for 1 minute. But, keep in mind that some certification houses MAY not agree with this premise. EN 50116 specifies a maximum current so that the test itself does not damage the circuit. If 25 amps is okay, and 30 amps is better, then why not 50 or 100 amps? If the current is high enough, then the circuit will indeed be damaged by the test. The requirement is that the grounding circuit, which handles the fault current return to the source, must be equally robust as the supply circuit which provides the current from the source (breaker) to the load. In practice, the supply circuit and the grounding circuit, both designed for 15 amps continuous, will easily handle twice that for a short period without overheating -- the wire may get warm, but it won't overheat! Hmm. Why don't we test the supply (primary) circuit for 30-amp fault current? It would be seem as bad for the supply circuit insulation to fail as it would for the grounding circuit to open! Well... answering my own question, the supply circuit would fail to the grounded metal, and the grounding circuit provides the protection. Best regards, Rich - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Grounding Bond Test
Hi Carmen: You ask how to resolve the difference between two, different production-line (routine) test standards. If your product is certified by CSA, then you test to the 30-ampere value. If your product is certified by a CB Certificate and Test Report, and the issuing body invokes EN 50116, then you test to the 25-ampere value. If your product is certified by UL, then you test to any current of your choosing. So, the answer to your question is: Whatever your certification house says. In essence, the requirement is proprietary to the certification house. The certification house can invoke any production-line test it feels is necessary. CSA uses 30 amps, 2 minutes. A certification house that invokes EN 50116 uses 25 amps, 1 minute as a maximum test. UL does not require a high-current test. The CSA 30-amp requirement derives from the fact that a CSA circuit-breaker rated 15 amperes (the most common 120-volt circuit in Canada) is not required to trip before 2 minutes at a current of twice rating, 30 amperes. So, the equipment grounding circuit must withstand 30-amperes for 2 minutes. The CENELEC 25-ampere requirement history is not at all clear. It has been in both European standards and UL standards as a type test for many, many years. It only appeared as a routine test when EN 50115 was published a few years ago. By the way, neither high-current test (as a production-line test) will identify continuity problems any better than a low-current test. The presumption is that the high-current test will identify a manufacturing defect in the grounding circuit, while a low-current test will not. In actuality, the grounding circuit, in order to pass the type test, had to be properly designed to handle the high current, no matter whether 25 amps or 30 amps. So, for the production-line, we need to be assured, by test, that the high-current circuit has been assembled correctly and with no defects. The high-current test WILL NOT identify loose screws if the conductors are making contact! The high- current test WILL NOT identify cut strands of wire if there are 3 or more strands in the circuit! (Feel free to duplicate these tests or any other grounding circuit defects you can imagine; the circuit will pass the high-current test!) The high-current test does not identify continuity problems any better than a low-current test. I did point this out to the EN 50116 committee when they asked for comments before it was published. Interesting that the committee ignored the data and required the test anyway! I guess the lesson is: don't confuse a technical committee with technical facts. Rich - Richard Nute Product Safety Engineer Hewlett-Packard Company Product Regulations Group AiO Division Tel : +1 858 655 3329 16399 West Bernardo Drive FAX : +1 858 655 4979 San Diego, California 92127 e-mail: ri...@sdd.hp.com - ps: In high-volume production, both the 1-minute and the 2-minute tests are unacceptable to the manufacturer. It seems that most certification houses will waive the long-term test in these cases! This seems to admit that the high-current test is not particularly valuable. - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Concrete as an insulator???
Hi Doug: Some years ago I did some tests on my concrete garage floor using aluminum foil laid down on the floor. I applied 120 volts through an ammeter to the foil, and then measured the current from the 120 volts to the foil. I wanted to learn how much current would be conducted by the concrete floor in the event someone was standing on the floor and touching a 120-volt live wire. As I recall, I put something on top of the foil to hold it in good contact with the concrete. With dry concrete, the current was tolerably low -- in the microamps. With wet concrete (I poured water onto the concrete, mopped up the puddle, and placed the foil on the concrete), the leakage current was in the low milliampere region. I would certainly caution about using as an insulator a material that is not rated as an insulator. Since the material is not evaluated as an insulator, there is no data on its performance. I would be hard pressed to use such a material as a reliable insulator. Good luck! Rich - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: FCC approved 3m chamber suitable for 10m qualification testing
Hello from San Diego: Please respond privately to Steve on this topic. We all need to protect both ourselves and the IEEE from possible libel or slander. If you want to discuss this request, please contact me privately. Thanks, and best regards, Richard Nute co-administrator, IEEE emc-pstc listserver. - Richard Nute Product Safety Engineer Hewlett-Packard Company Product Regulations Group AiO Division Tel : +1 858 655 3329 16399 West Bernardo Drive FAX : +1 858 655 4979 San Diego, California 92127 e-mail: ri...@sdd.hp.com - > Dear esteemed colleagues, > > Our small commercial laboratory lost a modest sized FCC verification test > and report to a competitor who DO NOT operate an OATS, but claim the > following.. > > "Our 3m semi-anechoic chamber measuring 18 ft. wide, X 28 ft. long and 28 > ft. high is FCC certified for testing Class A and Class B digital devices, > hence we are in compliance with ANSI C63.4/1992, CISPR 22 publication and > FCC Subpart B Class A regulations" > > If this is in flagrant violation with the FCC rules then I would like to > decide on a course of action suitable enough to grab the attention of those > who misrepresent our industry. Does anyone have experience with this same > problem or approached A2LA, NVLAP or FCC? > > Regards, > > Steve Reply-To: "Steve Kuiper" - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: U.S. National Product Safety "Laws"
Hi George: > I've read these sections of the CFR many times, and always interpreted them > to apply to end user equipment, as you imply. However, I am beginning to > see > that this may be somewhat like quoting the Bible out of context. The > context > in this section of the CFR (before and after) overwhelmingly refers to > "house" > wiring types of equipment. I don't agree that the text overwhelmingly refers to wiring (i.e., in OSHA words, "utilization system"). First, it would be derelict of OSHA to ignore the utilization equipment used by employees. One of the major construction site hazards was failure of insulation in portable electric tools. OSHA was the prime mover towards double-insulated electric tools! While our government often makes mistakes, they do NOT ignore "utilization equipment." Second, the text refers to "equipment" and to "utilization equiipment," both of which are defined terms. The definitions must be substituted EVERYWHERE the words appear in the text. When I apply the definitions, I cannot conclude as you do that the text refers "overwhelmingly" to wiring. > Is it only me, or do others have problems reading into this that it does > apply > to end user products such as ITE or blenders? With so many pages dedicated > to > describing the exact requirements for the construction of an "installation" > to > provide power to "equipment", why are there no pages dedicated to > describing the > requirements of the "equipment"? IEC 60950 contains 180 pages of such > requirements. The OSHA standard for electrical "equipment" is that it be "approved." "Approved" means "acceptable." "Acceptable" has three definitions, one of which is certified by an NRTL, one of which is testing to NEC provisions, and one of which is testing by the manufacturer. In this way, OSHA skirts having to publish individual product safety standards. As near as I can tell, OSHA did this overtly and after having thought it out rather extensively. OSHA realized that it could NEVER cover all electrical products with standards. > Note that covered equipment (whatever that may be) can be acceptable by > virtue > of the proper labelling/lisitng, or simply inspected and found to be safe by > one of the referenced authorities. Several have pointed out that such > authorities typically require a NRTL listing/marking. If your "proof" is > to be > interpreted as you (and I) have been interpreting it, then every single > electrical device sold in the U.S. would HAVE to have an NRTL marking. I > know > that a few years ago we were using internal PCs that bore no such markings. > I will not mention the brand name here. I suspect that one could find many > electrical products under $10 that do not display such markings either. Yes, ALL electrical equipment used by employees in the workplace must be "approved" (which means "acceptable" by one of the three definitions). (Obviously, OSHA ignores low-voltage and battery-operated equipment such as flashlights and calculators. I haven't located the "out" for these kinds of equipments.) If an OSHA inspector should find an electrical product that is not certified by an NRTL, I'm sure the employer will be notified! You can, of course, ask OSHA if the standards apply to ITE. I have no doubt of the answer. Best regards, Rich - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: U.S. National Product Safety "Laws"
Hi George: > So here is the challenge. Can anyone "prove" that 29 CFR 1900 > or the NEC specifically requires ITE to meet more than some > grounding/marking requirements, or be required to be approved by > an NRTL. Proof is citing clearly stated sections obviously > applicable to typical ITE products. Sorry, but vague references > to something "I once saw." are not allowed. Here is the proof you requested. Note that the wordings for "approval," "approved," and "equipment" of both OSHA and the NEC are identical! I wonder how that happened? :-) Best regards, Rich ... OSHA: = 1910.303 (a) Approval. The conductors and equipment required or permitted by this subpart shall be acceptable only if approved. 1910.399 (a) Definitions applicable to 1910.302 through 1910.330 - Acceptable. An installation or equipment is acceptable to the Assistant Secretary of Labor, and approved within the meaning of this Subpart S: (i) If it is accepted, or certified, or listed, or labeled, or otherwise determined to be safe by a nationally recognized testing laboratory; or (ii) With respect to an installation or equipment of a kind which no nationally recognized testing laboratory accepts, certifies, lists, labels, or determines to be safe, if it is inspected or tested by another Federal agency, or by a State, municipal, or other local authority responsible for enforcing occupational safety provisions of the National Electrical Code, and found in compliance with the provisions of the National Electrical Code as applied in this subpart; or (iii) With respect to custom-made equipment or related installations which are designed, fabricated for, and intended for use by a particular customer, if it is determined to be safe for its intended use by its manufacturer on the basis of test data which the employer keeps and makes available for inspection to the Assistant Secretary and his authorized representatives. Refer to 1910.7 for definition of nationally recognized testing laboratory. Approved. Acceptable to the authority enforcing this subpart. The authority enforcing this subpart is the Assistant Secretary of Labor for Occupational Safety and Health. The definition of "acceptable" indicates what is acceptable to the Assistant Secretary of Labor, and therefore approved within the meaning of this Subpart. Equipment. A general term including material, fittings, devices, appliances, fixtures, apparatus, and the like, used as a part of, or in connection with, an electrical installation. ... NEC: 110.Requirements for Electrical Installations. 110-2. Approval. The conductors and equipment required by this Code shall be acceptable only if approved. (FPN): See Examination of Equipment for Safety, Section 90-7, and Examination Identification, INstallation, and Use of Equipment, Section 110-3. See definitions of "Approved," "Identified," "Labeled," and "Listed." 100.Definitions. Approved: Acceptable to the authority having jurisdiction. Equipment: A general term including material, fittings, devices, appliances, fixtures, apparatus, and the like used as part of, or in connection with, an electrical installation. ... - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: U.S. National Product Safety "Laws"
Hi George: Just a clarification and amplification or your message... There are TWO laws that govern product safety: 1) OSHA. Your remarks thoroughly covered this law. 2) The National Electrical Code. This is a "model" building code intended for adoption by local building code jurisdictions. The NEC includes the requirement that all appliances must be "listed." It leaves to the jurisdiction to determine what constitutes "listed" and how to enforce it. All jurisdictions have an electrical code. Most adopt the NEC. A few write their own, e.g., Los Angeles, Chicago. Jurisdictions adopting electrical codes include the following governmental entities: - cities, e.g., Los Angeles, Chicago. - counties, e.g., San Mateo. - states, e.g., Washington, Oregon. These codes apply to new constructions and to alterations to exisiting constructions. Enforcement is by the electrical inspection of the installation. (Obviously, cord-connected appliances installed AFTER completion of the building electrical installation are not inspected for the "listed" mark.) At one time, the State of Oregon employed two inspectors who inspected electrical appliances and construction materials offered for sale in retail stores. If an appliance is found without a suitable mark, then the store is ordered by the State Electrical Board to remove the products from their shelves. The City of Los Angeles inspects appliances offered for sale at commercial shows. Any offered appliance without a NRTL mark is identified and a letter is sent to the manufacturer warning the manufacturer that any such product sold in Los Angeles must have a suitable certification mark. For all practical purposes, NRTL certification satisfies both the workplace law and the building code laws. Best regards, Rich - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: "National Safety Requirements"?????
Hi Kathy: > Someone who seemed to believe such a edict was sent > out resently asked me to check to I asked this group. > Maybe this is just a very bad joke from someone who > really doesn't know what he is asking. I wouldn't cross off the question this way. Be aware that there are a number of safety standards in the USA that COULD fit the definition of a "National Safety Requirement." Consider: 1. Any standard that is an American National Standard could fit the definition. Most UL standards are also American National Standards. 2. National Electrical Code, which is an American National Standard and is the basis for most U.S.A. product safety standards. Published by the NFPA, National Fire Protection Association. 3. National Electrical Safety Code, which is an American National Standard, published by the NFPA, National Fire Protection Association. This standard deals with protection of people in public and work places. Since each of these is an American National Standard, then it COULD be the one your colleague had in mind, but did not have the name correctly stated. Best regards, Rich - Richard Nute Product Safety Engineer Hewlett-Packard Company Product Regulations Group AiO Division Tel : +1 858 655 3329 16399 West Bernardo Drive FAX : +1 858 655 4979 San Diego, California 92127 e-mail: ri...@sdd.hp.com - - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Fault Testing Electrolytic Capacitors
Hi Bob: > A company I represent has a problem with their switching power supply. > A single point failure in the regulator can cause the output voltage to > rise higher than the voltage ratings of the electrolytic capacitors. As > a result, the capacitors are overstressed and fail in a variety of ways > depending upon the capacitor venting method. Sometimes the vent will > pop and thatÂ’s the end of it. Other times, the capacitor will overheat > and expel ethylene glycol in the form of vapor or liquid. In some > cases, the conductive fluid will bridge the primary circuits to earth > causing a failure of the hypot test. This is unacceptable for IEC950 > compliance. In my experience, the power supply is so designed that a failure does NOT cause the output voltage to exceed the voltage rating of the electrolytic capacitors. > I have spoken to several power supply designers and they inform me that > it is common practice not to provide overvoltage protection. Of course, > if that is true, then there appears to be a lot of power supplies in > the world, perhaps including the one in my pc, that may or may not pass > the fault testing of IEC950 depending on how the electrolytic > capacitors fail. Obviously, my client does not want the extra cost of > adding overvoltage protection when it appears that others donÂ’t do it. I've not seen power supplies with specific overvoltage protection for the electrolytic capacitors. We typically spec an output voltage range that includes maximum voltage under single-fault conditions. By so doing, the regulation scheme, including regulation under fault conditions, provides protection of the electrolytic caps. Your client will have to fix the power supply. (Others DO provide for protection against the effects of capacitor venting under fault conditions!) Best regards, Rich - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: CE enforcement
Hi Moshe:
> I need some "horror stories" on enforcement in Europe (to help convince
> some managers we
> really have to comply).
I look forward to reading the responses... BUT...
It is all too often that managers question the "regulatory"
laws of another country, but would not consider doing so for
the laws of the country in which they reside.
Anything that would cause us to change our "modus operandi"
is first rejected. The rejection is subject to change only
if supported by overwhelming evidence supporting the change.
The required evidence is comprised of:
If it is a law, then a copy of the law must be provided and
accompanied by a synopsis in terms understandable by
management. Even then, the synopsis will be questioned as to
accuracy. (The law will not be read by management.)
(We recently went through an exercise of determining whether
plug adaptors could be supplied with our products to adapt to
local country plugs. Then we could ship the USA plug every-
where in the world along with a package of adaptor plugs.
Plug adaptors are not specifically prohibited. But, plugs
must be certified to local requirements. If the USA plug
together with its adaptor does not meet local requirements,
then it cannot be certified and is therefore illegal. A
long way around, but that is the process by which adaptors
are not legal in most countries.)
Next, management will propose that the law be exorcised by
meeting with the officials and pointing out how ridiculus
the law is. (Management expects this process to work in
any other country except the country in which they reside.)
If this fails, then evidence ("horror stories") must be
provided to show that the law is actually enforced.
This process happens at our level, too. Consider your
reaction when a standard is revised such that you will need
to change something you are doing. Or, if you sit on a
standards committee, you will find that proposals to change
the standard are, at first, rejected. Then, upon persistance,
the change may eventually be processed.
Product safety engineers are timid, weak creatures. ;-) The
last thing we want to do is to tell an engineer (or management)
that a design does not meet the standard and that the product
will need to be changed. We will do (almost) anything to
avoid being the bearer of bad news. ;-) So, we fight every
change to the standard -- even if the change results in a more
safe product. After all, the current design has been good for
years, and we have no safety incidents that suggest a problem.
Rich
-
Richard Nute Product Safety Engineer
Hewlett-Packard Company Product Regulations Group
AiO Division Tel : +1 858 655 3329
16399 West Bernardo Drive FAX : +1 858 655 4979
San Diego, California 92127 e-mail: ri...@sdd.hp.com
-
-
This message is coming from the emc-pstc discussion list.
To cancel your subscription, send mail to majord...@ieee.org
with the single line: "unsubscribe emc-pstc" (without the
quotes). For help, send mail to ed.pr...@cubic.com,
jim_bac...@monarch.com, ri...@sdd.hp.com, or
roger.volgst...@compaq.com (the list administrators).
Joe Wujak
Posted on behalf of Bobbie Cronquist, John Wright, and Julie Gaevert. Some sad news about Joe Wujak, whom many of you may know and remember. Bobbie Cronquist - Forwarded message -- I have the very unfortunate task of telling everyone that Joe Wujek and his wife passed away recently in a car accident. Many of you on the S-PAC committee may not have had the chance to meet Joe, but he was one of the biggest "evangalizers" of S-PACs and S-PAVes as well as one of our most outstanding and most requested speakers. No matter where he went, on vacation or business, he would always take personal time to stop at the local school and talk to students about S-PAC. He served on the S-PAC committee and is the reason that I am involved today. Joe and his wife were on a wonderful vacation this summer on their way to see their son and daughter-in-law and 5 grand-children in Walla Walla, WA when the accident occured. I only met Joe's wife once, the day before the accident, because I had the pleasure of spending the day with them here in Seattle before they went on to Walla Walla. Those of you that knew Joe, know that when he believed in something, he was very passionate about it - he believed strongly in his students (he was a professor at Berkeley), he believed strongly in IEEE and even more so in ethics, which was one of his talks. In addition, he has spent many years fighting very hard to make sure that ethics stayed at the forefront of IEEE and the thoughts of all the engineers he taught. His daughter-in-law, who called me tonight, asked that I spread the work throughout IEEE and I would like to ask all of you to help me do this. Especially those of you in the Bay area. He was highly active in IEEE at all levels and well known throughout the section. There will be a service or them on Friday night, July, 23rd at 7:00 pm in Livermore, CA. It will be a Catholic Service, his daughter-in-law described it as a "celebration of their lives" and the name of the church is St Charles Borromeo. Address... 1315 Lomitas Ave, Livermore, CA 94550-6441 Phone: (925)447-4549. Please forward this information to those who knew Joe. Thank you. Julie Gaevert * * John L. Wright, Jr. * * Product Apps. Engr. Dept. Mgr. * * Cypress Semiconductor * * (408) 943-2886 x...@cypress.com* * * IEEE/R6/Central Area Chair 1999-2001 * * IEEE SF Bay Area Council SCV Director 1998/99 * * j.wri...@ieee.org (email for life)* * (408) 993-7227 (personal voicemail)* * - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: 10 N force Test on Internal Components Prior to Overvoltage Tests
Hi Peter: There are two schools of thought: 1) Clearance is an independent, stand-alone criterion. 2) Clearance determines electric strength of air and is an alternate means for determining the electric strength of air. If you are in the first school, then there is no reason to apply the force before or during the electric strength (or overvoltage) test. If you are in the second school, then you apply the force and measure the spacings. If you comply with the spacings, then apply the electric strength test. If the spacings were met during the force test, then the electric strength will be met during the electric strength test. The requirements apply equally to all circuits; no exemption for the telecom interface. Best regards, Rich - Richard Nute Product Safety Engineer Hewlett-Packard Company Product Regulations Group AiO Division Tel : +1 858 655 3329 16399 West Bernardo Drive FAX : +1 858 655 4979 San Diego, California 92127 e-mail: ri...@sdd.hp.com - - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Indoor use symbol -- what standards?
Hello from San Diego: What countries and what standards require the "indoor use: symbol? This symbol is comprised of a stick-figure house with an arrow pointing from outside to inside. My experience with this symbol is through TUV Product Service. They require its use because (they told me) it is required by a German standard for household use products. I do not know the standard. When TUV Product Service made me use the symbol, I asked for the standard reference and a printed example. They had none. So, one of their engineers drew the symbol and provided it to me. (This was some years ago.) The symbol is not in either the IEC symbol standard or the ISO symbol standard. I don't know of any product standard that requires the symbol. Perhaps one of the subscribers to this list can provide more information about what country and what standards require this symbol? Best regards, Rich - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Off Topic Maybe: Hydrogen Fuel Cells
Hi Doug: This subject is NOT in the "you got to be kidding me" category. Many years ago, such a fuel-cell generator was installed at IBM Kingston and ran for a year as an experiment. Since this is a SOURCE of electric energy, it falls into the same category as home wind generators and home solar generators. It's hooked up to the public utitilty with a suitable transfer switch for supplying your home or the utility or both. You can get such switches at Home Depot! No big deal. Spendy, but no big deal. Hydrogen storage and plumbing is a well-known construction. The fuel cell system outputs standard household voltage, current, and frequency. I believe it uses more-or-less standard electronic switching converters such as those used with a large UPS. Spendy, but no big deal. Best regards, Rich - Richard Nute Product Safety Engineer Hewlett-Packard Company Product Regulations Group AiO Division Tel : +1 858 655 3329 16399 West Bernardo Drive FAX : +1 858 655 4979 San Diego, California 92127 e-mail: ri...@sdd.hp.com - - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Product Safety Semantics
Hi John: > The subject here is regarding the words 'shall' vs. 'must' in various of > product safety standards (including UL 1950 3rd Ed. and EN60950). > > Does anyone have any insight into the definitions of these as applicable to > product safety? I have heard there are differences, but no one can seem to > give me an answer. The two words, "shall" and "must," are used interchangably. Both words are verbs. >From Webster's Collegiate Dictionary, 10th edition: shall: used in laws, regulations, or directives to express what is mandatory. etymology: OE shal: ought to, must must: be required by law, custom, or moral conscience to. etymology: OE moste: to be allowed to, to have to Clearly, by definition and by etymology, the words are nearly interchangable, at least insofar as usage in a standard. The word "shall" is predominant in IEC 950 and UL 1950; it appears throughout the standard. The word "must" appears in the following sub-clauses: 1.2.7.3 Text 1.7.2 Notes 2.7.1 Note 5.2.2 Compliance 6.3.2 Text Fig. 19 Notes Annex NAA3.4, Requirement Annex NAA6.4.4.2, Example Annex NAAAnnex NAB Example Annex NAE Text Annex NAE2.5.9 Topic/Summary Annex NAE3.1.12 Topic/Summary Annex NAE3.2.1 Topic/Summary Annex NAE3.3Topic/Summary Annex NAE3.3.5 Topic/Summary Clearly, most of the "musts" are in UL 1950 addenda, not in IEC 950. In context, it is very difficult to ascribe a meaning to "must" that is different from "shall." (Identifying the word in the text is an easy exercise with an electronic copy of the standard and an application with a "find" function.) Best regards, Rich - Richard Nute Product Safety Engineer Hewlett-Packard Company Product Regulations Group AiO Division Tel : +1 858 655 3329 16399 West Bernardo Drive FAX : +1 858 655 4979 San Diego, California 92127 e-mail: ri...@sdd.hp.com - - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Fuse rating
Hi Rick: > If a product has a 4A rated input current (120V AC), how does one > determine the rating of the in-line Fuse for safety/Fault testing? There is no relationship between input rating and the fuse rating. The input rating is the maximum input under normal operating conditions. The fuse rating is less than the worst-case (not maximum) input under fault conditions. The first problem is to identify faults that can occur in the primary circuit. The fault you are looking for is that fault that creates the least current at which some component overheats to the point of destroying insulation, e.g., change of color of plastic or PWB material, or softening of EMI filter bobbin, or? SMPS components that are candidates for overheating include the EMI filter, the bridge rectifier, the snubber resistor, the snubber diode, the switching transistor, the current-sampling resistor, transient suppressors, the transformer, connectors, etc. Most of these components overheat as a result of excessive current through the device. These devices will couple the heat to nearby various polymeric or organic materials. One big sign of overheating is the color change of the PWB or plastic materials. One way of creating overheating events is to put a humungous variable resistor (e.g., 0-10 ohms) in parallel with various primary circuit components. Reduce the value of the resistor, and watch for signs of heating of the other components. Monitor the ac input current. The worst-case input is the least fault current that causes unacceptable overheating. Once you have determined the least fault current, then you select a fuse that is rated one-half of that fault current. (Fuses do not operate at 100% rated current at normal temperatures; fuses operate at 200% rated current in less than one minute.) Typical fuse rating should be about twice rated current (or more). (Of course you must balance the fuse value with the duration of normal peak currents.) Enjoy! Rich - Richard Nute Product Safety Engineer Hewlett-Packard Company Product Regulations Group AiO Division Tel : +1 619 655 3329 Effective 6/12/99: +1 858 655 3329 16399 West Bernardo Drive FAX : +1 619 655 4979 Effective 6/12/99: +1 858 655 4979 San Diego, California 92127 e-mail: ri...@sdd.hp.com - > From owner-emc-p...@majordomo.ieee.org Thu May 13 12:12:54 PDT 1999 > Received: from hpsdlo.sdd.hp.com (hpsdlo-sw.sdd.hp.com [15.26.112.11]) by > hpsdlfsg.sdd.hp.com with ESMTP (8.7.6/8.7.3 TIS 5.0/sdd epg) id MAA17861 for > ; Thu, 13 May 1999 12:12:53 -0700 (PDT) > Received: from ruebert.ieee.org (ruebert.ieee.org [199.172.136.3]) > by hpsdlo.sdd.hp.com (8.8.6 (PHNE_14041)/8.8.5btis+epg) with ESMTP id > MAA20003 > for ; Thu, 13 May 1999 12:12:50 -0700 (PDT) > Received: by ruebert.ieee.org (8.8.8+Sun/8.8.8) > id OAA23315; Thu, 13 May 1999 14:21:07 -0400 (EDT) > Message-ID: > > From: Rick Loiselle > To: "EMC-Safety (E-mail)" > Subject: Fuse rating > Date: Thu, 13 May 1999 14:21:42 -0400 > MIME-Version: 1.0 > X-Mailer: Internet Mail Service (5.5.2232.9) > Content-Type: multipart/alternative; > boundary="_=_NextPart_001_01BE9D6D.739BAE72" > Sender: owner-emc-p...@majordomo.ieee.org > Precedence: bulk > Reply-To: Rick Loiselle > X-Resent-To: Multiple Recipients > X-Listname: emc-pstc > X-Info: Help requests to emc-pstc-requ...@majordomo.ieee.org > X-Info: [Un]Subscribe requests to majord...@majordomo.ieee.org > X-Moderator-Address: emc-pstc-appro...@majordomo.ieee.org > > > This message is in MIME format. Since your mail reader does not understand > this format, some or all of this message may not be legible. > > --_=_NextPart_001_01BE9D6D.739BAE72 > Content-Type: text/plain; > charset="iso-8859-1" > Content-Transfer-Encoding: quoted-printable > > Greetings Group, > =A0 > If a product has a 4A rated input current (120V AC), how does one > determine the rating of the in-line Fuse for safety/Fault testing? > =A0 > The Fuse will be used at the AC connector Inlet, inside the product = > (not > user accessible) on the Hot lead wire.=A0 I do know that it will be an = > in-line > type fuse > holder, UL and CSA approved, 5X20. > =A0 > We test to UL6500 and IEC 60065. > =A0 > Best Regards,=20 > Rick=20 > =A0 > > --_=_NextPart_001_01BE9D6D.739BAE72 > Content-Type: text/html; > charset="iso-8859-1" > > > > > > > > RE: Car Audio Amplifiers > > > > > color=#00 face=Arial size=2>Greetings Group, > size=2>Â > If a product has a 4A rated input current > (120V > AC), how does one > dete
Re: Transmission Line Theory
Hi Allen: I'll take a shot at this one! (At one time I dealt with high- fidelity high-frequency signals where the effects of connectors could be observed in the waveforms.) The ideal transmission line is terminated at both ends with its characteristic impedance. In some circumstances, you can "cheat" by not providing a termination (i.e., open or short) at either the source end or the load end, depending on what you want to accomplish. If you terminate at the load end, then no standing waves and no reflections back to the source. So, the source can be any impedance without degrading the signal, and you get twice the voltage. If you terminate at the source end, then you get a standing wave, and reflections. The reflections are terminated in the source impedance and don't distort the pulse at the source. I presume this is your situation -- terminating at the source. I'm afraid I have no idea of what is radiated from the transmission line, but I would guess that it would be a lot because of the standing wave. If you change impedance, you get standing waves or reflections, but not as much amplitude as a short or open. There are impedance-matching attenuators which act as a termination for one transmission line and as a source impedance for the other transmission line. Lossy. There is leakage from transmission lines. I would expect rather high leakage from a PWB transmission line (compared to coax). As one colleague once stated, the whole world is a transmission line. In fact, he calculated the characteristic impedance between the earth and the moon! 377 ohms??? Best regards, Rich - Richard Nute Product Safety Engineer Hewlett-Packard Company Product Regulations Group AiO Division Tel : +1 619 655 3329 Effective 6/12/99: +1 858 655 3329 16399 West Bernardo Drive FAX : +1 619 655 4979 Effective 6/12/99: +1 858 655 4979 San Diego, California 92127 e-mail: ri...@sdd.hp.com - - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: ignition points for ...
Hi George: > Can anyone point me to a resource (Book, Chart etc) that lists ignition > points for various (flammable) materials ? Flash-ignition temperatures and self-ignition temperatures for various generic plastic materials are published in: International Plastics Flammability Handbook Jurgen Troitzsch Hanser Publishers, Munich, Vienna, New York Distributed in the United States and Canada by Oxford University Press ISBN 3-446-15156-7 Carl Hanser Verlag ISBN 0-19-520797-1 Oxford University Press More ignition temperatures for plastics, woods, paper, and textiles are published in: Flammability Handbook for Plastics -- Third Edition Carlos J. Hilado Technomic Publishing Company 265 Post Road West, Westport, Connecticut 06880 ISBN 087762-306-6 This book also contains data for glass transition temperatures decomposition temperatures specific heat thermal conductivity oxygen index ignition times heat release and much other data. Similar data is published in: Flammability Handbook for Electrical Insulation Carlos J. Hilado Technomic Publishing Company 265 Post Road West, Westport, Connecticut 06880 ISBN 87762-316-3 For an electrically-caused fire, there are three significant factors: 1. Temperature. The temperature of the electrical device must be greater than the self-ignition temperature of the candidate fuel material. 2. Thermal energy. The thermal energy coupled to the candidate fuel material must exceed the energy necessary to raise the fuel material to self-ignition temperature. 3. Thermal coupling. The thermal energy from the electrical device must be coupled into the fuel material at a rate very much greater than the thermal conductivity of the candidate fuel material. Without all three parameters, ignition of the fuel material is not possible. Best regards, Rich - Richard Nute Product Safety Engineer Hewlett-Packard Company Product Regulations Group AiO Division Tel : +1 619 655 3329 Effective 6/12/99: +1 858 655 3329 16399 West Bernardo Drive FAX : +1 619 655 4979 Effective 6/12/99: +1 858 655 4979 San Diego, California 92127 e-mail: ri...@sdd.hp.com - - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Mains DC
Hi Peter: > The Dielectric Voltage Withstand Table in UL1950/EN 60 950 lists > equipment with "Mains DC". What does this mean? You make it difficult to answer this question because you used a term that does not appear in UL 1950: Mains DC I did an electronic search of the standard for this term; there is no such term. The term that is used is: d.c. mains The only place this term is used is in the notes to Table 18, "Test voltages for electric strength tests." In some cases, equipment may be made to operate from a d.c. mains rather than an a.c. mains. The point of notes 6, 7, and 8 accompanying Table 18 is to identify the electric strength test voltages for equipment intended to be connected to a d.c. mains supply. Best regards, Rich - Richard Nute Product Safety Engineer Hewlett-Packard Company Product Regulations Group AiO Division Tel : +1 619 655 3329 Effective 6/12/99: +1 858 655 3329 16399 West Bernardo Drive FAX : +1 619 655 4979 Effective 6/12/99: +1 858 655 4979 San Diego, California 92127 e-mail: ri...@sdd.hp.com - - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Heat Calculation
Hi Lauren: At the risk of being shown otherwise... > Determining the actual heat dissipation of your product could be very time > consuming. It would involve, in part, knowing the electrical efficiency of I would argue that, using the law of conservation of energy, this is not at all time consuming, and is really quite easy. The product takes in electrical energy. All of this energy must be accounted for in terms of dissipation of that energy -- in some form other than electrical energy. Most of the components are energy transducers -- they change the electrical energy into some other form of energy. Resistors, semiconductors, inductors, transformers, and some capacitors all dissipate electrical energy in the form of thermal energy. LEDs and CRTs dissipate electrical energy into both thermal energy and light energy. Motors transform electrical energy into both thermal energy and kinetic energy. (The kinetic energy is then dissipated in friction which converts the kinetic energy to thermal energy.) Charging a battery converts electrical energy to thermal energy and chemical energy. The vast majority of the electrical energy is dissipated as thermal energy. Best regards, Rich - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Heat Calculation
Hi Scott: Under the law of the conservation of energy, all of the energy going into a product must be accounted for. Energy is measured in joules. One joule is one watt-second. One watt is one joule/second. All of the watts entering the product must be accounted for. All of the watts are converted to some other form of energy. If the product has moving parts, some of the electrical energy is converted to kinetic energy. (The kinetic energy is ultimately converted to thermal energy in the friction of the mechanical system.) If the product has light output (i.e., LEDs, CRT), some of the electrical energy is converted to light energy. (This conversion is very inefficient; very little energy is converted to light energy.) If the product has semiconductors and resistors and similar devices, some of the electrical energy is converted to thermal energy in those devices. So, for all practical purposes, all of the electrical energy is converted to thermal energy. One watt is 3.41443 BTU/hour. So, for all practical purposes, the product dissipates 3.41443 BTU/hour/watt. If your product is disspating 1000 BTU/hour, then its input must be 1000/3.41433 or 293 watts The BTU/hour is a function of the input power (watts). If the input power changes from product to product, then the BTU/hour must likewise change from product to product. Best regards, Rich - Richard Nute Product Safety Engineer Hewlett-Packard Company Product Regulations Group AiO Division Tel : +1 619 655 3329 Effective 6/12/99: +1 858 655 3329 16399 West Bernardo Drive FAX : +1 619 655 4979 Effective 6/12/99: +1 858 655 4979 San Diego, California 92127 e-mail: ri...@sdd.hp.com - - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Excessive smoke
Hi Jeff: > If a component abnormal test generates excessive and sustained smoke > (several minutes), but does'nt breach reinforced or double insulation, nor > emit flame from the enclosure, is it considered a failure? Intuitively, it > seems like it would be, because of toxicity, but I have been unable to find > anything in the safety standards to support this. I have checked EN 60950, > EN 50178, UL 1012, and CSA C22.2 No. 107.1. For the purposes of product safety and compliance with safety standards, smoke is a "permitted" emission during fault testing. The safety issue is whether a safeguard is damaged or breached due to the heat which produced the smoke. If insulation is not damaged (as per the hi-pot test), and excessive heat or flame does not breach the enclosure (as per the cheesecloth test), then the product is considered acceptable for the purposes of product safety. Typically, product safety standards do not address the toxicity of smoke. This is because all smoke contains toxic materials. The only solution to smoke toxicity is to eliminate smoke, which means eliminating all overheating situations. Which is nearly impossible. However, any smoke from a product is likely create fear and anxiety in the mind of the user and nearby persons. Any smoke in a clean room will likely be cause for scrapping all stock in the clean room. While smoke always contains toxic materials (e.g., carbon monoxide), the concentration of the smoke (toxic material) in the volume of the room together with the room ventilation determines whether or not inhalation of the smoke is likely to cause an injury. If the volume of smoke is small compared to the volume of the room, then it is likely the concentration of toxic material will be below the TLV (threshold limit value) for that material. So, it is a good idea (for the satisfaction of your customers) to eliminate or reduce any significant smoke emissions that might occur during fault testing. Best regards, Rich - Richard Nute Product Safety Engineer Hewlett-Packard Company Product Regulations Group AiO Division Tel : +1 619 655 3329 Effective 6/12/99: +1 858 655 3329 16399 West Bernardo Drive FAX : +1 619 655 4979 Effective 6/12/99: +1 858 655 4979 San Diego, California 92127 e-mail: ri...@sdd.hp.com - - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Conductive Paint, Round 2
Hi Jeff: > I need to clarify my earlier question on conductive paint. We bond our > enclosure panels together with screws. We use external-tooth starwashers > between the screws and sheet metal to achieve a reliable, protective-earth > bond. On our painted panels, we mask the paint so that the starwasher makes > good contact with the metal. We are now considering using conductive paint > without masking, but we would still use starwashers. I don't see how this > could be a problem, but it's not something I've seen done before and so I'd > like your input. The main point to keep in mind is that conductive paint is resistive, and not near zero ohms. I presume that the need to ground the panels is for safety, not necessarily for EMC. If for EMC, then disregard these comments. There are two scenarios to consider: 1) Star washer tooth cuts through the conductive paint and contacts the panel; electrical connection is direct from the panel to the star washer. 2) Star washer tooth does not cut through the conductive paint; electrical connection between the panel and the star washer is through the conductive paint to the points and the flat surface of the star washer. 1) This scenario is nearly the same as the masked paint scenario. The current path is two fold: a) from the panel directly to the teeth of the star washer, and b) from the panel to the conductive paint to the flat part of the star washer. Since this latter path is likely to be higher resistance, most of the current will pass through the points of the star washer. 2) This scenario may suffer due to the electrical resistance of the paint and the contact area of the star washer with the paint. Presume that the teeth of the star penetrate the conductive paint, but not all the way through to the metal panel. The teeth of the star washer will establish an equipotential environment within the conductive paint. Therefore, all of the current from the paint to the star washer will be through the teeth of the washer, not through the flat portion of the star washer. When subjected to the 25- or 30-ampere fault current. the paint may vaporize at each tooth of the star washer, and the ground connection will be lost. This can be easily tested with a simple experiment using a high-current dc power supply. My personal opinion is that reliance on conductive paint for safety is not a good idea. The reason behind this opinion is the fragility of the paint to both current density and physical scratches. (This reasoning follows the same reasoning why fragile enamel and varnish wire insulation is not relied upon for safety insulation.) Best regards, Rich - Richard Nute Product Safety Engineer Hewlett-Packard Company Product Regulations Group AiO Division Tel : +1 619 655 3329 Effective 6/12/99: +1 858 655 3329 16399 West Bernardo Drive FAX : +1 619 655 4979 Effective 6/12/99: +1 858 655 4979 San Diego, California 92127 e-mail: ri...@sdd.hp.com - - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Conductive Paint
Hi Jeff: > My company is proposing to use conductive paint on our enclosures, and I > would like your input as to the acceptability of this vis-a-vis protective > earth bonding of enclosure panels. I am interested in the perspective of > both European and North American requirements. The implication of your question is whether conductive paint can be used to carry fault current in the event of an insulation fault to the conductive paint. In my experience, effective bonding of conductive paint requires large-area contacts to the paint. This is because the paint has a very small cross-sectional area, so the current from the paint to the grounding circuit must be distributed with large-area contacts, i.e., emc finger stock. Some certifiers may question whether such contact mechanisms constitute bonding as defined in the various safety standards. But, this only addresses the grounding of the conductive paint. A fault to the paint would start with a point contact and may grow to a large-area contact depending on the nature of the fault. Regardless of whether or not the fault connection is large-area, at the instant of contact, it will be a small-area contact. The initial current density at the point of contact to the conductive paint will be extremely high. This high current will cause the conductive paint to vaporize, and the connection to ground will immediately open. (You can perform this experiment by touching a live, 120-volt or 230-volt 18 AWG or 0.75 mm wire to the grounded painted surface.) For this reason, conductive paint will not be effective as a part of a protective earth circuit. However, the paint can be grounded -- it just cannot be designated as a part of the protective earth circuit, and it need not be grounded through bonding techniques. The implication is that your construction employs a plastic enclosure with grounded conductive paint on the inner surface. You can designate the plastic material as supplementary insulation, and thereby achieve compliance with safety requirements throughout the world. If you choose to designate the plastic as supplementary insulation, you will need to test the insulation for electric strength. This will be easy. You wrap the outer side of the plastic in conductive foil and apply the test voltage between the inner conductive paint and the foil. You need to keep the paint away from accessible parts of the enclosure to prevent breakdown around edges and through holes. Regards, Rich - Richard Nute Product Safety Engineer Hewlett-Packard Company Product Regulations Group AiO Division Tel : +1 619 655 3329 Effective 6/12/99: +1 858 655 3329 16399 West Bernardo Drive FAX : +1 619 655 4979 Effective 6/12/99: +1 858 655 4979 San Diego, California 92127 e-mail: ri...@sdd.hp.com - - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: IEC 950 Insulation Requirements
Hi George: > Along this line, I was asked, if placing power and ground traces on > separate (PCB) layers would be an acceptable way of reducing clearance > requirements between (gnd&pwr) traces. Is there anyway to anticipate > clearance between PCB layers of a multi layered board? Is there a need to > as far as 950 is concerned? I haven't been able to find anything that > mentions this. Supposedly, the insulation between traces on separate PCB layers should constitute solid insulation (not clearance). Therefore, the requirements of Sub-clause 2.9.4.1 should apply. Depending on the insulation, the 0.4 mm requirement for reinforced solid insulation may apply. (There is no dimensional requirement for solid basic insulation.) This is a three-dimensional problem. The 0.4 mm applies in all three dimensions with respect to plated-through holes. Also, at the edges of the board, the construction must meet the applicable creepage distance if the inner layer conductors extend to the edge of the board. The issue is complicated by certification houses who require proof that the insulation bonds within the board comply with Sub-clause 2.9.7, "spacings filled by insulating compound." This sub-clause requires proof that no voids or cracks are likely in the solid insulation provided by the prepreg layers. Such PCB multilayer construction may be difficult to prove. You should take up this question with your certifier, as the applicability of the requirements to multi-layer PCBs may vary with the certifier. (UL 1950 Second Edition "Application Guidelines," number 2.9.4-001 implies acceptance of multi-layer glass fiber PCBs as supplementary or reinforced insulation between layers. However, this same guideline does not appear in the current "Guidelines.") I'm surprised the PCB design would require power and ground on separate layers. Most primary power circuits can be adequately insulated from ground without using multi-layer technology. In my experience, the only use of ground in power supply circuits is for the return of the Y capacitors, which need not have 25-amp capability. But, if the power circuit is a secondary power circuit, then such construction may effectively use multi-layer technology. Best regards, Rich - Richard Nute Product Safety Engineer Hewlett-Packard Company Product Regulations Group AiO Division Tel : +1 619 655 3329 Effective 6/12/99: +1 858 655 3329 16399 West Bernardo Drive FAX : +1 619 655 4979 Effective 6/12/99: +1 858 655 4979 San Diego, California 92127 e-mail: ri...@sdd.hp.com - - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Argentinean Power Cord
Hi Ali: > Today I received a call from one of distributors stating that as of August > of this year, Argentina will have their own power cord requirements. I > believe Argentina has the same configuration as Australia. Does anyone know > where I can find out more about this requirement? Check the following URLs: http://www.panelcomponents.com/guide/patterns.htm#C http://kropla.com/electric.htm (click on "inverted v") The Argentina plug does not have the same configuration as Australia, although there are a lot of similarities and the Australian plug might (probably will) work. But, as in most other countries, Argentina national certification is (or soon will be) required, and therefore the Australia plug will be outlawed because of its differences and lack of Argentina national certification. Volex offers Argentina approved power cords. See: http://www.volex.com/powercords/POWPROD4.HTM Note that Volex offers BOTH Argentina approved power cords AND Australia approved power cords, but these are separate cords. This says that there ARE differences, with the implication that they are not interchangable. Regards, Rich - Richard Nute Product Safety Engineer Hewlett-Packard Company Product Regulations Group AiO Division Tel : +1 619 655 3329 Effective 6/12/99: +1 858 655 3329 16399 West Bernardo Drive FAX : +1 619 655 4979 Effective 6/12/99: +1 858 655 4979 San Diego, California 92127 e-mail: ri...@sdd.hp.com - - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Equipotential bonding.
Hi John: > In the CB Scheme "National Differences" document, Danish and Norwegian > requirements (in 6.3.3.1 and 6.2.1.2, respectively) make reference to > "equipotential bonding". Can anyone tell me exactly what equipotential bonding > is? I assume that it is some form of grounding...would having a permanent > connection to protective earth satisfy this requirement? "Equipotential bonding" is the name given to the general case, while "grounding" or "earthing" are the names given to a specific case of equipotential bonding. Equipotential bonding is a scheme of protection against electric shock. All conductive parts in the local environment, e.g., a room, are bonded together to create an equipotential environment. If there is no potential difference in the environment, then there is no possibility of electric shock. (This is the principle behind bonding all conductive parts within electrical equipment together.) In practice, all conductive parts in the environment cannot be bonded together. Instead, all conductive parts of electrical equipment are connected to ground via the protective conductor in the power cord. Likewise, all other conductive parts in the room, e.g., plumbing, heating ducts, etc., are connected to ground via some other means. This is not a perfect equipotential environment, but it is functional and practical. The flaw is that during a fault to the equipment metal, there is a voltage drop across the resistance of the protective conductor that can allow the voltage on the equipment metal to be as high as 1/2 the mains voltage (with respect to other grounded parts) until the overcurrent device operates -- which can be as long as 2 minutes. So, an electric shock condition could exist for those 2 minutes. If a true equipotential environment was established with local (i.e., in the same room) bonding, then the voltage drop across the protective conductor would not create a potential difference between the equipment and the remainder of the environment (because they are all bonded together within the room). So, no electric shock condition would exist. Best regards, Rich - Richard Nute Product Safety Engineer Hewlett-Packard Company Product Regulations Group AiO Division Tel : +1 619 655 3329 Effective 6/12/99: +1 858 655 3329 16399 West Bernardo Drive FAX : +1 619 655 4979 Effective 6/12/99: +1 858 655 4979 San Diego, California 92127 e-mail: ri...@sdd.hp.com - - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
dc-to-ac inverter.
Hi Doug: > My question is this, is it because the inverter has a low voltage input and > they do not have to comply to a standard like EN61010 or UL1950, or is this > something the manufacturers haven't addressed because no one has ever asked? I don't think anyone but the manufacturers can answer your question. It is certainly easy to say that because the unit is rated for less than 50 V input, it is exempt from the LVD. The inverter is essentially a UPS with an external battery and without the monitoring and switchover features. So, the applicable safety standards would be those for UPS. In the USA, under the NEC, the inverter would be considered a separately-derived source. The NEC requires such sources to be grounded. At 300 watts output and 12 volts, the input current would be more than P 300 I = - = --- = 25 amperes E 12 Assuming at least 60 watts consumed in the inverter operation, input current would be 30 amperes! So, one major safety issue is that of overheating (and fire) due to normal and fault-mode currents. Another major safety issue is the isolation of the 120 volts from the 12 volts. Yet another is that of grounding, both the neutral and protective conductors, of the 120-volt source. So, there are real safety issues with such an inverter. Best regards, Rich - Richard Nute Product Safety Engineer Hewlett-Packard Company Product Regulations Group AiO Division Tel : +1 619 655 3329 Effective 6/12/99: +1 858 655 3329 16399 West Bernardo Drive FAX : +1 619 655 4979 Effective 6/12/99: +1 858 655 4979 San Diego, California 92127 e-mail: ri...@sdd.hp.com - - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: US/ HAR line Cord
Hi Ray: > I know that at one time, UL had accepted a HAR type cordset. Now, I have ... ... > Does anyone know why UL stepped back away from accepting EU cords? My guess is: UL accepts HAR cordage (not cordsets) for products going to countries where the HAR certification is accepted. UL does not accept HAR cordage in the USA because the HAR cordage does not meet the UL/ANSI standards for cordage. Likewise UL/ANSI cordage does not meet HAR requirements. It would be nice if the IEC could develop a single cordage standard that could be accepted worldwide. I don't really believe that cordage needs to be country- or region-unique as it is today. Likewise, safety is not a function of national borders because all men are created equal. Its disappointing to see Argentina set up its own safety certification program and not accept the worldwide CB system. Regards, Rich - Richard Nute Product Safety Engineer Hewlett-Packard Company Product Regulations Group AiO Division Tel : +1 619 655 3329 Effective 6/12/99: +1 858 655 3329 16399 West Bernardo Drive FAX : +1 619 655 4979 Effective 6/12/99: +1 858 655 4979 San Diego, California 92127 e-mail: ri...@sdd.hp.com - - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Building Main Transformer causes Video Problems
Hi John: > He sees the video distorted and was wondering > about any health risks. The first thing you should do is ascertain that the distortion is caused by an external source or an internal (to the monitor) source. It is possible that the degauss circuit has failed, in which case you will get a distortion that remains constant with position of the monitor. The cause of the distortion is likely to be the magnetic interference from the transformer. You can test for this by rotating the monitor (in which case the shape and color should change), and by moving the monitor further away from the transformer (in which case the shape and color should change and diminish). Note that a permanent magnet near the screen has a similar effect, but over a limited area. A good web site that cites magnetic exposure standards is: http://www.lessemf.com/standard.html 60-Hertz magnetic exposure limits range from 2.5 mG to 10 G, depending on the standard. There is little agreement as to both the effect on the body and the exposure limit. If you go to the home page, you will find some more (highly pessimistic) info and some good (not necessarily pessimistic) links. There is some data describing possible health risks, but remember that there is little substantial research in the effects of magnetic fields upon the body. Best regards, Rich - Richard Nute Product Safety Engineer Hewlett-Packard Company Product Regulations Group AiO Division Tel : +1 619 655 3329 Effective 6/12/99: +1 858 655 3329 16399 West Bernardo Drive FAX : +1 619 655 4979 Effective 6/12/99: +1 858 655 4979 San Diego, California 92127 e-mail: ri...@sdd.hp.com - - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Mains to the inside of a safe.
Hi Peter: I understand the construction to be that of a mains extension from a wall outlet outside the safe via a plug to two socket-outlets inside the safe. Your question is "Does the safe now fall under the LVD?" Plugs, mains cordage, and socket-outlets are NOT included in the LVD as they are subject to national standards. However, a wiring harness would be under the LVD if it is not under the national wiring standards, i.e., those standards equivalent to IEC 60364. The LVD would cover the isolation between the mains circuits and the battery circuits, and the isolation between the mains circuits and the metal of the safe. As to the applicable standard for the isolation, it would probably be IEC 60335, household appliances. It might, however, be IEC 60065, household electronic equipment. I don't think IEC 60950, IT equipment, is particularly applicable. Best regards, Rich - Richard Nute Product Safety Engineer Hewlett-Packard Company Product Regulations Group AiO Division Tel : +1 619 655 3329 Effective 6/12/99: +1 858 655 3329 16399 West Bernardo Drive FAX : +1 619 655 4979 Effective 6/12/99: +1 858 655 4979 San Diego, California 92127 e-mail: ri...@sdd.hp.com - - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
When a fire enclosure is required...
Hi Jim: You ask a number of questions about fire enclosures for IT equipment. > Section 4.4.5 of UL1950 appears to require a fire enclosure for essentially > anything that contains a printed circuit board assembly Sub-clause 4.4.5.1 essentially says that all conductors and components must be in a fire enclosure. Sub-clause 4.4.5.2 specifies four exceptions. One of those exceptions is for components in a TNV circuit supplied by a power source limited to 15 VA under both normal and single- fault conditions. This exception is independent of whether or not the components are mounted to a printed wiring board. (One of the other exceptions requires components be mounted on a printed wiring board rated V1 or better.) > We have a max of 94Vrms on our cards (obviously isolated from SELV circuits) > with a power less that 15VA. I am assuming that this means that > a fire enclosure is necessary based upon my interpretation of the exceptions > above (TNV requirement). My reading of the requirement is that a 94-volt rms source with less than 15 VA under both normal and single-fault conditions does NOT need to be in a fire enclosure. The criterion is 15 VA, and is independent of the voltage. > Unfortunately, we are also trying to optimize air flow through the enclosure > meaning that any type of screen or baffles (or anything necessary to make > this > a fire enclosure) significantly reduces the air flow. If the circuit is less than 15 VA, then I would expect that cooling would not be necessary. * The construction you describe doesn't match with your questions. So, I'm now assuming that your circuit exceeds 15 VA and therefore requires a fire enclosure. > Is it possible to design the enclosure and then have it tested to A.2 to > detemine if we meet the requirements of a fire enclosure.? > it seems that a fan located in a "fire enclosure" (and therefore compliance > not necessarily checked) may be just as hazardous to the spread > of fire out of the top of the enclosure. Openings are permitted in fire enclosures. The permitted openings will allow sufficient cooling for most circuits. See Sub-clause 4.3.14, 4.3.15, and 4.3.16. The test described in Annex A.2 essentially requires a plastic material rated V-1 or V-0 or 5-V. So, you can test the enclosure material to A.2. If you use UL-certified material rated V-1, V-0, or 5-V you do not need to perform the test of A.2. It is true that a fan may contribute to a fire and spread of fire by supplying an increased supply of oxygen as well as a spread of heat. A fan may do the opposite by creating a too lean fuel-air mixture to sustain a fire. Both of these are difficult to predict. The fire enclosure and opening requirements specified in UL 1950 are presumed to contain a fire, whether or not a fan is present. Best regards, Rich - Richard Nute Product Safety Engineer Hewlett-Packard Company Product Regulations Group AiO Division Tel : +1 619 655 3329 Effective 6/12/99: +1 858 655 3329 16399 West Bernardo Drive FAX : +1 619 655 4979 Effective 6/12/99: +1 858 655 4979 San Diego, California 92127 e-mail: ri...@sdd.hp.com - - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Protective Earthing Terminal
Hi Peter: > Question 1: Can we rely on the two screws securing the appliance > inlet as a means for bonding? Over the years, I have been told by > various safety agencies that such construction is unacceptable. The appliance coupler you describe MUST include an integral EMC filter with metal cover, not just a plain, ordinary, all-insulated appliance coupler. An ordinary appliance coupler cannot be grounded by its own mounting screws as the screws attach the insulated part of the coupler to the chassis. If the appliance coupler is fitted with an integral EMC filter, then the ground terminal of the appliance coupler passes through the EMC filter to the filter metal cover to a second earthing terminal. This extension of the ground terminal must meet all the original requirements for the appliance coupler earthing terminal. Usually, the EMC filter earthing terminal is securely attached to the filter cover such that the filter cover meets all of the requirements of the coupler earthing terminal. Given this construction, the coupler mounting screws can provide the necessary bonding required for safety. In fact, the bonding scheme has two screws, one of which provides a redundant connection. >From a certification house point of view, this construction does not provide a separate and distinct scheme of bonding the coupler earthing terminal to the chassis. And, it is difficult to identify a mounting screw as the earth bonding terminal with the symbol. Furthermore, most safety standards require that earth bonding connections be solely used for that function. Hence, the mounting screws for the appliance coupler cannot also be used for the earthing connection. This interpretation will vary with your particular certification engineer as well as with the particular certification house. If you want the construction to be unequivocably judged acceptable, use the separate wire to a separate stud. Otherwise, you must be prepared to argue, and be prepared to use a stud if you lose the argument. This is not an issue of safety. It is an issue of clearly and unequivocably complying with the standard. > Question 2: Am I correct in assuming that the appliance earthing > terminal for the above Listed/Certified products was considered as > the main protective earthing terminal? This is a good question without a clear answer. The main protective earthing terminal would be the one marked with the upside-down tree in a circle (IEC 417, 5017). Note that this symbol is molded into the appliance coupler. It may or may not appear on the EMC filter cover. Also note that the stud is also marked with the same symbol. Which, then, is the main earthing terminal? According to IEC 60950, Sub-clause 1.7.7.1: "The wiring terminal intended for connection of the protective earthing conductor associated with the supply wiring shall be indicated by the symbol (IEC 417, 5017)." The conductor from the supply wiring is connected to the appliance coupler. Therefore, the earthing terminal of the appliance coupler is the main earthing terminal. IEC 60950 seems to recognize the appliance coupler marking as indicating the equipment main earthing terminal. See the exemptions to Sub-clause 1.7.7.1. However, many certification engineers and certification houses believe that the point of attachment of the appliance coupler earth terminal to the chassis is the main earthing terminal. Again, if you want the construction to be unequivocably judged acceptable, apply the marking next to the stud. > Question 3: Why do most other ITE manufacturers use the "stud > on the chassis method" for protective earthing terminal? Already discussed. Tradition, and because such construction is unequivocably acceptable. Best regards, Rich - Richard Nute Product Safety Engineer Hewlett-Packard Company Product Regulations Group AiO Division Tel : +1 619 655 3329 Effective 6/12/99: +1 858 655 3329 16399 West Bernardo Drive FAX : +1 619 655 4979 Effective 6/12/99: +1 858 655 4979 San Diego, California 92127 e-mail: ri...@sdd.hp.com - - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Leakage Current Measurements
Hi Frank: > Interesting. During an audit of the facilities of a former employer, the > auditor specifically requested that we didn't use the Simpson 228 for > EN60950 because of the roll-off of the analog movement above 100Hz. The > suggested fix was to build the network as described in the standard, with a > high frequency true RMS digital meter. Analog (D'Arsonval) meter movements are dc devices. AC input is rectified and applied to the meter movement. Any roll-off is a function of the frequency response of the rectifier circuit, not the analog movement (since it only sees dc). Furthermore, the network has a built-in roll-off such that very little high frequency energy is actually applied to the measuring device. If your auditor had applied a constant voltage, variable frequency ac source to the Simpson 228, he would indeed see a roll-off, the one that is due to the frequency compensation network specified in IEC 990. He would see exactly the same roll-off with the discrete network and a wide-bandwidth true-RMS digital meter. Best regards, Rich ps: I do not understand the source of leakage current that is other than the mains frequency. In a switching-mode power supply, virtually all of the high-frequency currents are returned to the source via the EMC filter. Are there other sources that are multiples (harmonics) of the mains frequency? - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: conductive part definitions
Hi Pete: It seems to me that there are several kinds of conductive parts that we need to be concerned about from a safety perspective: 1. Energized parts at hazardous voltage. 2. Energized parts at non-hazardous voltage. 3. Energized parts at non-hazardous current. 4. Grounded/earthed parts. 5. Non-grounded/earthed parts susceptible of becoming energized at a hazardous voltage in the event of a fault. 6. Non-grounded/earthed parts not susceptible of becoming energized at hazardous voltage in the event of a fault. For the purpose of these definitions, grounded/earthed is taken as meaning bonded to the earth. Non-grounded/earthed is taken as meaning not bonded to the earth, but may be incidentally connected to earth (i.e., not connected to earth in a manner that assures a current- carrying capability). Each of the preceding parts can be either accessible or inaccessible. (The safety standards prohibit some of these parts from being accessible.) According to your definitions: > Exposed conductive part: conductive part of equipment, which can be > touched and which is not normally live, but which can become live when > basic insulation fails. Exposed conductive part = My definition 5, and accessible. > Extraneous/non-electrical conductive part: conductive part not > forming part of the electrical installation and liable to introduce an > electric potential, generally the electric potential of a local earth. Extraneous/non-electrical conductive part = My definition 6. Your question: Which is a better term for the definition, extraneous or non-electrical? In the sense of this discussion, a conductive part is implied to be an electrically-conductive part. So, a non-electrical electrically-conductive part could be taken as an oxymoron. Its certainly not clear as to what is meant. Let's review Webster's Collegiate Tenth: Extraneous: 1) existing on or coming from the outside; 2a) not forming an essential or vital part; 2b) having no relevance; 3) being a number obtained in solving an equation that is not a solution to the equation. So, it seems the word "extraneous" is consistent with the definition of the part. Best regards, Rich - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Leakage Current Measurements
> A meter for IEC 60950 may not be adequate for IEC 61010, > especially if the unit under test has a reasonably high > frequency switch mode power supply. The high frequencies generated in a switching mode power supply are negligible in the presence of the mains-frequency leakage current (presuming that the SMPS as even a mediocre EMC filter). Even if high frequencies are present in the leakage current, the various leakage current measurement schemes use a capacitor to shunt the high frequencies around the metering circuit. The body response to electric energy falls off rapidly for frequencies above 1 kHz. At 100 kHz and above, the injury changes from shock to burn, and the limit is 70 mA peak (50 ma rms!). Consequently, the leakage current meters include frequency compensation to account for the body response. Around the turn of the century, D'Arsonval performed an experiment where he lit a 100-watt bulb at a frequency between 10 and 100 kHz with ALL of the current passing through the human body! No injury! Richard Nute San Diego - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Leakage Current Measurements
> From owner-emc-p...@majordomo.ieee.org Fri Mar 12 02:24:22 PST 1999 > Received: from hpsdlo.sdd.hp.com (hpsdlo-sw.sdd.hp.com [15.26.112.11]) by > hpsdlfsg.sdd.hp.com with ESMTP (8.7.6/8.7.3 TIS 5.0/sdd epg) id CAA28353 for > ; Fri, 12 Mar 1999 02:24:21 -0800 (PST) > Received: from ruebert.ieee.org (ruebert.ieee.org [199.172.136.3]) > by hpsdlo.sdd.hp.com (8.8.6 (PHNE_14041)/8.8.5btis+epg) with ESMTP id > CAA00549 > for ; Fri, 12 Mar 1999 02:24:20 -0800 (PST) > Received: by ruebert.ieee.org (8.8.8/8.8.8) > id EAA14981; Fri, 12 Mar 1999 04:38:08 -0500 (EST) > Message-ID: <286215c2ca1ad211a13500a024535b58424...@eukscpo3.dundee.ncr.com> > From: "Crabb, John" > To: "'pe...@itl.co.il'" , emc-p...@ieee.org > Subject: RE: Leakage Current Measurements > Date: Fri, 12 Mar 1999 09:35:40 - > MIME-Version: 1.0 > X-Mailer: Internet Mail Service (5.0.1460.8) > Content-Type: text/plain > Sender: owner-emc-p...@majordomo.ieee.org > Precedence: bulk > Reply-To: "Crabb, John" > X-Resent-To: Multiple Recipients > X-Listname: emc-pstc > X-Info: Help requests to emc-pstc-requ...@majordomo.ieee.org > X-Info: [Un]Subscribe requests to majord...@majordomo.ieee.org > X-Moderator-Address: emc-pstc-appro...@majordomo.ieee.org > > We use a Yokogawa 3226 Universal Leakage Current Tester > together with a 3227 Test Box. The meter has both an "AC" and > an "AC+DC" current range, and switchable 1K, 1.5K, and 2K > input resistance. The test box has a polarity and an on-off switch to > simplify testing, and has a US mains socket into which we plug the > product to be tested, using a cord with the earth pin cut off, which we > can also readily reverse. > UL and CSA seem quite happy to use this meter when they come here > to review our products. > We also have a Simpson 229-2 which is there to be used if the other > meter is being calibarated, and it gives similar results to > the Yokogawa. > I asked UL to bring their Simson 228 meter here during a recent > investigation, to compare results. It read a little higher than the > Yokogawa, but UL were happy for us to continue using the Yokowawa. > They certainly do not insist on the use of the Simpson 228. > > I had some information on a Hioki Model 3155-01 Leakage Current > Tester, which is claimed to meet the latest IEC 950 requirements, but > I can't readily lay my hands on it. IT WAS EXPENSIVE. > It is a digital meter, could also measure the voltage/current going > to the equipment, and had pluggable networks for 950 and medical > equipment measurements. > > >From time to time when I am doing leakage current measurements, > I check that the results I get ARE VERY SIMILAR to the reading I > get if I just put the meter in series with the ground conductor of the > product. (And they are always almost identical) Could somebody > explain why this much simpler method is not used ? > > John Crabb, Development Excellence (Product Safety) , > NCR Financial Solutions Group Ltd., Kingsway West, Dundee, Scotland. DD2 > 3XX > E-Mail :john.cr...@scotland.ncr.com > Tel: +44 (0)1382-592289 (direct ). Fax +44 (0)1382-622243. VoicePlus > 6-341-2289. > > > - > This message is coming from the emc-pstc discussion list. > To cancel your subscription, send mail to majord...@ieee.org > with the single line: "unsubscribe emc-pstc" (without the > quotes). For help, send mail to ed.pr...@cubic.com, > j...@gwmail.monarch.com, ri...@sdd.hp.com, or > roger.volgst...@compaq.com (the list administrators). > > - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: NRTL requirement in the NEC?
Hi Jeff: Quotes from the 1996 NEC: "110-2. Approval. The conductors and equipment required or permitted by this Code shall be acceptable only if approved." "Approved: Acceptable to the authority having jurisdiction." "90-7. Examination of Equipment for Safety. For specific items of equipment and materials referred to in this Code, examinations for safety made under standard conditions will provide a bais for approval where the record is made generally available through proumlgation by organizations properly equipped and qualified for experimental testing, inspections of the run of goods at factories, and service- value determination through field inspections. This avoids the necessity for repetition of examinations by different examiers, frequently with inadequate facilities for such work, and the confusion that would result from conflicting reports as to the suitability of devices and materials examined for a given purpose. "It is the intent of this Code that factory-installed internal wiring or the construction of the equipment need not be inspected at the time of installation of the equipment, except to detect alterations or damage, if the equipment has been listed by a qualified electrical laboratory that is recognized as having the suitable facilities described above and that requires suitability for installation by this Code." So, the NEC requires all parts to be certified. If the rack has a certification label on it indicating the whole thing is certified, then the inspector will stop there. If the rack does not have such a label, then the inspector is entitled to look at the individual parts included in the rack for certification labels. It is true that a power supply can be evaluated as a component of the system. If this is the case, then the system must bear a certification label. If the inspector does not accept that the power supply is included in the system certification, then providing him with a copy of the certification report will clarify that problem. Best regards, Rich - Richard Nute Product Safety Engineer Hewlett-Packard Company Product Regulations Group AiO Division Tel : +1 619 655 3329 16399 West Bernardo Drive FAX : +1 619 655 4979 San Diego, California 92127 e-mail: ri...@sdd.hp.com - - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Awards for Worst EMC/PS qualities
Most of the stories are stories about EMC fixes. I've got one that is not and won't be fixed. I just live with it! It involves my '96 Honda Accord, bought new. I'm in San Diego, about 100 miles south of Los Angeles. I noticed that 50 kW Los Angeles AM stations such as KFI and KNX were really quite noisy on my car radio. So, too, are some of the local, San Diego AM stations. When I pull into my garage (in my stucco home with chicken-wire EMC shielding), the signals disappear into the noise. I chalked it up to poor AM design of the radio, or to the rear window antenna. (No whip antenna on this Honda!) One day, upon arriving at work, I turned off the ignition, but left it in the accessory position. The radio noise disappeared and the radio was clear! I repeated the same thing as I pulled into my garage. While there was some noise, most of it disappears when the ignition is turned off. The noise appears as soon as the ignition is turned on, and before the engine is started. Starting the engine has no effect on the noise. The AM radio is almost useless except for the strongest stations! Unless the iginition is off. Best regards, Rich - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Rack System Safety (UL1950/EN 60950) Questions
Hello from San Diego: I said: > > 1. For the North America, does a NEMA 125 V, 20 A plug meet the > > pluggable B definition? > > No. The objective of the Pluggable Type B connection is that > of a reliable, non-defeatable earth connection. The NEMA 20 A > plug uses the same earthing connection as the NEMA 15 A plug. > The 15 A plug is notorious for having the earthing connection > destroyed or removed in use. A colleague has pointed out that the NEMA 20 A plug is indeed accepted by some North American certification houses as meeting the Pluggable Type B definition. The thinking is twofold: 1) the 20 A receptacle is ALWAYS a grounding type, and 2) the 20 A plug is not subject to the same abuse as the 15 A plug. Best regards, Rich - Richard Nute Product Safety Engineer Hewlett-Packard Company Product Regulations Group AiO Division Tel : +1 619 655 3329 16399 West Bernardo Drive FAX : +1 619 655 4979 San Diego, California 92127 e-mail: ri...@sdd.hp.com - - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Rack System Safety (UL1950/EN 60950) Questions
Hello Peter: > 1. For the North America, does a NEMA 125 V, 20 A plug meet the > pluggable B definition? No. The objective of the Pluggable Type B connection is that of a reliable, non-defeatable earth connection. The NEMA 20 A plug uses the same earthing connection as the NEMA 15 A plug. The 15 A plug is notorious for having the earthing connection destroyed or removed in use. > 2. What are some plug configurations which will meet the > pluggable B equipment requirements for North America and > Europe? I'm afraid I can't answer this question. I suggest you ask UL or CSA. > 3. Does anyone have experience with UL and/or CSA and/or TUV > when testing a unit employing a Recognized/Certified/Approved > computer type "totally enclosed" power supply? I am interested to > know if temperatures should be monitored within such a power > supply. So far, I have been asked to thermocouple various points > within the power supply and as you all know, it could get very > crowded in there. I am interested to know if someone out there > knows if such a waiver exists for totally enclosed Approved power > supplies. Any component, including component power supplies, must be tested for temperature rise in the end-product configuration. It is not necessary to measure all of the same points as was done for the power supply safety qualification. I choose a sub-set of those, especially the highest temperatures. If the highest temperatures are okay in the end-product, then it is a good assumption that the lower temperatures are also okay. I would expect that you would only need to test 20% of the total test points. > 4. When conducting stability tests for rack systems, should all the > serviceable card cages be extended out or is it enough to do it one > at a time. Testing is almost always the worst-case condition, regardless whether such condition is not expected in normal service. "Doors, drawers, etc., which may be moved for servicing by the operator or by service personnel are placed in their most infavourable position, consistent with the manufacturer's instructions." > 5. For a CSA NRTLC unit employed in the rack system, does > anyone know if the CSA NRTLC Mark is automatically accepted by > UL or does UL require that the unit must be re-investigated and > placed under their Follow-Up Program? The CSA NRTL mark means the unit is acceptable for use in any USA workplace. The unit need not be also certified by UL. If CSA certifies the unit to the bi-national standard, then the certification is accepted by UL if you should submit the unit to UL as part of another equipment. Otherwise, it does not make much sense to also submit the unit to UL. Both CSA and UL and all other NRTLs have follow-up programs. This is a NRTL requirement. > 6. Has the US Robotics Listed "Sporster" card modem been > evaluated to UL1950 Third Edition? If so, such certification would be marked on the unit or on the packaging accompanying the unit. In addition, it would appear in the UL Listed Products book. > 7. Can I List/Certify a rack system to UL1950 Third Edition if the > units within it have been Listed/Certified to UL1950 First and/or > Second Editions? I do not think so, but am interested to hear your > opinions. No. All certifications of components and sub-systems must be to the same or newer edition of the standard as for the entire equipment. (In most cases, certification to newer editions also means compliance to former editions.) By the way, the differences between editions rarely mean the hardware does not comply with newer requirements. Re-evaluating the hardware to the newer editions rarely results in a need to change the hardware. Its an exercise which costs the submittor money, and benefits the certifier, but has no effect on the safety of the equipment, and has no benefit to the customer. I have several products certified to IEC 60950 Amd 1, 2, and 3. We're adding some new models to these families. All new models must now be evaluated to Amds 1, 2, 3, and 4. No hardware changes, but I must go through a complete new evaluation because Amd 4 is now in effect. Since safety is realized in the hardware, and since there is no hardware change, what is the value of Amd 4? > 8. How is a CB test report done for a rack system which consists > of previously Listed/Certified/Approved units? Does the CB scheme > Recognize the Approvals of the various test agencies > (UL/CSA/TUV)? A CB for a rack system must include CBs for each of the individual parts of the system. Or, each individual part must be evaluated in accordance with the standard. The NCB can use the listing/certification/ approval reports from other NCBs to reduce the amount of evaluation of those parts. But, the CB Report it issues must cover everything in the rack, either directly included in the CB Report or included as attachment CB Reports. Be
Re: High voltage fuse and holder
Hi Moshe: > I need fuses and fuse holders for 10kV line. Can someone tell me who is > making these (or what > are other altenatives to current limiting on high voltage lines)? 10 kV fuses are BIG! I checked the Littlefuse web site and found a "medium voltage" fuse rated 14,400 volts, 0.5 amp and up. This fuse is 12 inches long, 1-5/8 inches in diameter! HUGE! (Of course, its interrupt rating is 80,000 amperes.) I suspect you don't want something this big. I also suspect you don't have 80,000 amperes to interrupt. So, without knowing anything about your circuit or applciation... * Check out the various fuse manufacturers. * If the 10 kV is derived from a lower voltage, fuse the low voltage side. * Use a low-voltage side electronic overcurrent detector. * Put a low-voltage current sense in the grounded return leg to the transformer. Use the output to control the primary. Best regards, Rich - Richard Nute Product Safety Engineer Hewlett-Packard Company Product Regulations Group AiO Division Tel : +1 619 655 3329 16399 West Bernardo Drive FAX : +1 619 655 4979 San Diego, California 92127 e-mail: ri...@sdd.hp.com - > From owner-emc-p...@majordomo.ieee.org Mon Mar 8 13:48:01 PST 1999 > Received: from hpsdlo.sdd.hp.com (hpsdlo-sw.sdd.hp.com [15.26.112.11]) by > hpsdlfsg.sdd.hp.com with ESMTP (8.7.6/8.7.3 TIS 5.0/sdd epg) id NAA20570 for > ; Mon, 8 Mar 1999 13:48:01 -0800 (PST) > Received: from ruebert.ieee.org (ruebert.ieee.org [199.172.136.3]) > by hpsdlo.sdd.hp.com (8.8.6 (PHNE_14041)/8.8.5btis+epg) with ESMTP id > NAA10299 > for ; Mon, 8 Mar 1999 13:47:59 -0800 (PST) > Received: by ruebert.ieee.org (8.8.8/8.8.8) > id PAA20702; Mon, 8 Mar 1999 15:52:45 -0500 (EST) > From: mvald...@netvision.net.il > Date: Mon, 8 Mar 99 22:50:47 PST > Subject: High voltage fuse and holder > To: emc-p...@ieee.org > X-PRIORITY: 3 (Normal) > X-Mailer: Chameleon 4.6, TCP/IP for Windows, NetManage Inc. > Message-ID: > MIME-Version: 1.0 > Content-Type: TEXT/PLAIN; charset=US-ASCII > Sender: owner-emc-p...@majordomo.ieee.org > Precedence: bulk > Reply-To: mvald...@netvision.net.il > X-Resent-To: Multiple Recipients > X-Listname: emc-pstc > X-Info: Help requests to emc-pstc-requ...@majordomo.ieee.org > X-Info: [Un]Subscribe requests to majord...@majordomo.ieee.org > X-Moderator-Address: emc-pstc-appro...@majordomo.ieee.org > > Hello everyone, > > I need fuses and fuse holders for 10kV line. Can someone tell me who is > making these (or what > are other altenatives to current limiting on high voltage lines)? > > thanks in advance, > moshe > > Name: moshe valdman > E-mail: mvald...@netvision.net.il > Phone: 972-52-941200 > Telefax: 972-3-5496369 > Date: 8/3/99 > Time: 22:50:47 > You are most welcome to visit my homepage at: > > http://www.geocities.com/CapeCanaveral/5233/ > > > > - > This message is coming from the emc-pstc discussion list. > To cancel your subscription, send mail to majord...@ieee.org > with the single line: "unsubscribe emc-pstc" (without the > quotes). For help, send mail to ed.pr...@cubic.com, > j...@gwmail.monarch.com, ri...@sdd.hp.com, or > roger.volgst...@compaq.com (the list administrators). > > - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: LED safety
Hi Moshe: > Can someone enlighten me on the status of safety of using LED's as > indicators. Are they still > to be suspected as radiation sources (60825) and what should I do in the > design (?) to prove > them safe? EN 60950 Amd 11 invokes EN 60825. EN 60825 applies to ALL lasers and LEDs. EN 60825 establishes emission classes and safeguards for each class. The indicator LEDs I have in my products are Class I. As such, no safeguards are required, including labelling. However, it is necessary to DECLARE Class I emissions. As a general rule, indicator LEDs are taken as Class I without test. This is similar to accepting a 1.5-volt battery as low voltage without test. However, I don't have any test data to prove the indicator LED is Class I if I were to be challenged. I do ask the LED manufacturer for his declaration that his LED is Class I under maximum current (since emissions are measured with the single worst-case fault introduced into the equipment). Most LED manufacturers are not aware that EN 60825-1 applies also to non-lasing LEDs. They have no experience in testing to EN 60825-1, and often make major mistakes in their testing and calculations. Most LED manufacturers are happy to test at rated current, but are reluctant to test at anything above rated current as such operation is outside of specs. They don't understand that safety must be maintained even with the worst-case single fault. Fortunately, most indicator LEDs self-destruct before they exceed Class I emission. Best regards, Rich - Richard Nute Product Safety Engineer Hewlett-Packard Company Product Regulations Group AiO Division Tel : +1 619 655 3329 16399 West Bernardo Drive FAX : +1 619 655 4979 San Diego, California 92127 e-mail: ri...@sdd.hp.com - - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Earth Continuity Test
Hi Raymond: >Does anyone know why the standard selects 25A, not others? The presumption is that a zero-impedance fault occurs between the live mains and the protective earth/ground circuit. This means the full current of the mains will flow in the protective earth/ground circuit until the overcurrent device operates. The value of 25 amperes (for 1 minute) approximates the worst-case current and duration for operation of a mains overcurrent device such as a fuse or circuit-breaker. For example, fuses are required to operate in no more than one minute at twice rated current. So, if the mains circuit is protected with a 15-amp fuse, the fault current would be 30 amps for no more than 1 minute. (This is why CSA requires a test at 30 amps.) Circuit-breakers are required to operate in no more than four minutes at twice rated current. It is generally accepted (and it is largely true) that if the circuit can withstand 25 amperes for one minute, it can withstand 25 amperes or more for several minutes. Best regards, Rich - Richard Nute Product Safety Engineer Hewlett-Packard Company Product Regulations Group AiO Division Tel : +1 619 655 3329 16399 West Bernardo Drive FAX : +1 619 655 4979 San Diego, California 92127 e-mail: ri...@sdd.hp.com - - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
