Re: Short circuit tests in GR-1089
Hello All: Just a quick followup on our discussion about the short circuit tests: I just received my copy of Issue 3 of GR-1089, and when I went to replace Issue 2 I found a 1-page bulletin from Telcordia, dated December 1999, tucked in the front of my Issue 2 binder. The bulletin specifically addresses the permissible response of equipment to the short circuit test. Following is the text from that bulletin: It is the Telcordia Technologies interpretation that when the short-circuit is applied to a circuit pack the operation of a fuse, circuit breaker, semiconductor fuse (e.g., diode, transistor, FET), and/or other current-limiting means (e.g., fold-back) without a fire, electrical safety, or fragmentation hazard is permissible. Further, it is the Telcordia interpretation that a sacrificial element such as a fuse, diode(s), transistor(s), semiconductor, or polymer over-current device(s) may fail as part of this test. The circuit pack is not required to be operational following this test. However, compliance shall be demonstrated by application of cheesecloth as specified in GR-1089-CORE, Section 4.5.2. I think the above statement clears up most, but not all, of the uncertainty regarding permissible failure modes under Issue 2. Of course, now we have Issue 3 with language that is not identical to this earlier statement. Joe Randolph Telecom Design Consultant Randolph Telecom, Inc. 781-721-2848 http://www.randolph-telecom.com --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list
RE: Short circuit tests in GR-1089
All, I agree with the concept that the short circuit is not always worst case. I have seen many ITE power supplies shut down with a sc, but an output overload lets the smoke out. One problem with a trace opening is the reliability of that opening in a safe manner. When a certified fuse blows, we can generally trust it will blow in the same manner under a sc or overload in the field, due to the tight manufacturing constraints and agency testing on certified fuses. When a trace burns out, do we know how reliable it is? Repeated tests to verify the reliability may be in order. Whether the standard requires it (I haven't researched it), I would consider it due diligence. Sam Davis Regulatory Engineer Professional Testing Inc. (512)244-3371 x112 www.ptitest.com -Original Message- All - In consideration of the proliferation of SMPS in electronic equipment, it is not unrealistic to expect a simple short-circuit might not meet the intent of GR-1089. While many linear supplies will run indefinitely under sc, most SMPS will go into hysteresis or shut down completely under a solid sc. A reasonable test condition is just below the current limit of the SMPS output. While I also dislike a PWB trace opening, we are considering a fault condition and the compliance criteria are related to failing in a safe manner. As well, once a trace opens, it is most likely the assembly/subassembly will be discarded, rather than reused, since it will not function correctly and not be considerable repairable. Regards, Peter L. Tarver, PE Product Safety Manager Sanmina-SCI Homologation Services San Jose, CA peter.tar...@sanmina-sci.com Richard Hughes wrote: Perhaps some will take issue with me in applying a partial short in addition to a dead short. In my defence I will say that I work for a manufacturer and not a test lab and the reality is that failed capacitors are unlikely to have a zero ohm impedance when they fail in real life. The question then becomes one of how far should one go to minimise product liability? Richard Hughes In a message dated 11/27/2002, Joe Randolph writes: The only remaining gray area is whether the failure of a component or circuit trace is acceptable *provided* that it is located on the same circuit card where the short was induced, *and* that no safety hazard resulted. My interpretation is that this would be acceptable. --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list
RE: Short circuit tests in GR-1089
Remember that Telcordia documents are private and copywrited. I was advised by persons at Telcordia that as of October 2002 GR-63-CORE 1995 would no longer be available as the grandfathering period would be expired. Also since GR-1089 issue 3 has no grandfathering period, I was advised by Telcordia that issue 2 should now be out of print. Verizon accepted the 2002 version of GR-63 at the NEBS seminar in Vegas last month after Telcordia agreed to a couple changes in the fire section and airborne contaminants section. Telcordia has sent out change notices to folks on thier subscription list. As far as GR-1089, if issue 2 is not available anymore, new copies could only be obtained by breaking copyright laws. I do not know Verizons position on issue 3, but since it is generally more stringent than issue 2 or provides clarification, and does not conflict with thier new checklist, I would assume they would be favorable, but that will be thier decision. The other 3 RBOC's participated in the development of issue 3, so they should be OK with it. However it will be tough for manufacturers to get things tested to the old version if it is out of publication. In which case Verizon may need to write thier own version of GR-1089 so that it is available to the public or accept the new issue 3. These are my opinions and not necessarily those of my employer. Jim Jim Wiese NEBS Project Manager/Senior Compliance Engineer ADTRAN, INC. 901 Explorer Blvd. P.O. Box 14 Huntsville, AL 35814-4000 256-963-8431 256-963-8250 fax jim.wi...@adtran.com -Original Message- From: Gary McInturff [mailto:gary.mcintu...@worldwidepackets.com] Sent: Wednesday, November 27, 2002 6:05 PM To: j...@aol.com; t...@world.std.com; emc-p...@majordomo.ieee.org Subject: RE: Short circuit tests in GR-1089 Last I heard, and please correct me if not, was that Verizon had rejected the new standards much to the chagrin of the rest of the industry. Gary -Original Message- From: j...@aol.com [mailto:j...@aol.com] Sent: Wednesday, November 27, 2002 1:07 PM To: t...@world.std.com; emc-p...@majordomo.ieee.org Subject: Re: Short circuit tests in GR-1089 Hello All: Many thanks to all who responded to my question about this requirement. Many of the responses were quite interesting and persuasive, even though some of them were directly opposed. I think that the expanded description in the new third edition of GR-1089 helps resolve most of the uncertainty I had with regard to this requirement. I was not aware that the new edition of GR-1089 had been issued, so this discussion was doubly useful. Telcordia has now received some of my $$ for a copy of the new edition. Joe Randolph Telecom Design Consultant Randolph Telecom, Inc. 781-721-2848 http://www.randolph-telecom.com --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All
RE: Short circuit tests in GR-1089
All - In consideration of the proliferation of SMPS in electronic equipment, it is not unrealistic to expect a simple short-circuit might not meet the intent of GR-1089. While many linear supplies will run indefinitely under sc, most SMPS will go into hysteresis or shut down completely under a solid sc. A reasonable test condition is just below the current limit of the SMPS output. While I also dislike a PWB trace opening, we are considering a fault condition and the compliance criteria are related to failing in a safe manner. As well, once a trace opens, it is most likely the assembly/subassembly will be discarded, rather than reused, since it will not function correctly and not be considerable repairable. Regards, Peter L. Tarver, PE Product Safety Manager Sanmina-SCI Homologation Services San Jose, CA peter.tar...@sanmina-sci.com Richard Hughes wrote: Perhaps some will take issue with me in applying a partial short in addition to a dead short. In my defence I will say that I work for a manufacturer and not a test lab and the reality is that failed capacitors are unlikely to have a zero ohm impedance when they fail in real life. The question then becomes one of how far should one go to minimise product liability? Richard Hughes In a message dated 11/27/2002, Joe Randolph writes: The only remaining gray area is whether the failure of a component or circuit trace is acceptable *provided* that it is located on the same circuit card where the short was induced, *and* that no safety hazard resulted. My interpretation is that this would be acceptable. --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list
RE: Short circuit tests in GR-1089
Hello Dave, Actually this is incorrect. Damage to any component in the fault current path refers to items like inductors or resistors which may be in the -48V return or frame ground path. If they were to open, an exposed metallic surface may become ungrounded and become a safety hazard. The new GR-1089 attempts to clear up the intent although the definition of fault current path is somewhat ambiguous and could be mis-interpreted. It is my interpretation as well as several test labs that the fault current path is the one that protects the equipment from unsafe conditions or physical exposure as the result of a fault such as a short circuit within the equipment. It is not necessarily the current path of the short circuit itself. Thus opening a fuse or other sacrificial component in the DC supply path is fine as long as there is not an electrical safety hazard generated, a fire hazard occurring, or a ground trace/wire (example of fault path) that opens (even by the old GR-1089). Telcordia has explained this at NEBS seminars dating back as far as 1996 and in an industry letter a few years ago. Regards, Jim Jim Wiese NEBS Project Manager/Senior Compliance Engineer ADTRAN, INC. 901 Explorer Blvd. P.O. Box 14 Huntsville, AL 35814-4000 256-963-8431 256-963-8250 fax jim.wi...@adtran.com -Original Message- From: Dave Spencer [mailto:dspen...@dsl-only.net] Sent: Tuesday, November 26, 2002 12:24 PM To: '' Subject: RE: Short circuit tests in GR-1089 Hi All, My $.02 worth... I strongly disagree with what has been said regarding operation of output fuses. You may have a case for input fuses/circuit breakers. It is my belief that the purpose of this test, which is a cross referenced follow through to the design requirements now contained in GR-78, is to ensure that the circuit board has been designed to handle fault currents and is reliable. As has come up here before, a dead short is not the maximum fault current that a given power supply will see. It is more likely to be an ohm or two (silicon short) that fails to activate the crowbar circuit and the short should be applied using an adjustable power resistor tweaked to a maximum current reading. You are expected to discover if your PCB surface traces, via plating, and thermal relief (if used) are sized correctly for the maximum current produced by a fault condition. If you have a fuse in-line with the output of your supply, you FAIL the test! The requirement is quite plain: R9-20[92] For both grounded and ungrounded power supplies, conformance to this requirement shall be demonstrated by the absence of damage to equipment, conductors and conductor insulation, and ANY COMPONENT of the fault current path. One will note that it does not say any component except fuses or circuit breakers. To meet this requirement, you will have designed a supply that will not be subjected to failure from incidental short circuits. One may argue that this is not fair, but let us not forget that NEBS is all about reliability. It not only must be safe, but it needs to work in foreseeable misuse environments so we can continue to enjoy that dial tone each and every time we pick up the handset. If one wishes to design, build, and test telecommunications equipment to the standard of excellence defined by NEBS, one must digest the whole family of documents defined as FR-2063, not just the requirements of GR63/GR1089. Have a Great Day, Dave Spencer Two Peppers -Original Message- From: owner-emc-p...@majordomo.ieee.org [mailto:owner-emc-p...@majordomo.ieee.org] On Behalf Of Lou Aiken Sent: Monday, November 25, 2002 10:38 PM To: Ted Rook; j...@aol.com; Subject: Re: Short circuit tests in GR-1089 I'd like to add that the product need not operate correctly after a fault condition causes a fuse to open, it must only remain safe - within the meaning of the standard. Regards, Lou Aiken, LaMer LLC 27109 Palmetto Drive Orange Beach, AL 36561 USA tel ++ 1 251 981 6786 fax ++ 1 251 981 3054 - Original Message - From: Ted Rook t...@crestaudio.com To: j...@aol.com; emc-p...@ieee.org Sent: Monday, November 25, 2002 5:25 PM Subject: Re: Short circuit tests in GR-1089 I'm not an expert on GR1089 but I think that your interpretation should include careful consideration of what constitutes damage. The operation of a fuse or a circuit breaker is not damage. That is normal operation. What the specification is seeking to eliminate is overheating, explosion, loss of insulating properties, improper sizing of conductors and improper sizing of connections, all of which may give rise to damage under short circuit conditions. If the fuse blows and the fuseholder bursts into flames then that is a problem. If the fuse blows and everything fails safe, and normal operation can be restored by replacement of a fuse then no hazardous condition has been created. Does this help? Best Regards Ted Rook, Console Engineering, ext 4659
RE: Short circuit tests in GR-1089
Joe, It is quite common for local filtering consisting of an inductor followed by a capacitor to be added in the logic-level supply rail following an on-board DC:DC converter when powering sensitive ICs. Often there are many such filters on each card and it is not feasible to fuse each of them individually. If you short, or partially short (low resistance) the output capacitor then you can reach a condition where the DC:DC converter keeps pumping power into the fault and either the inductor fails or the output tracks burn up. [Of course, this is just one example of many where components are placed in series with the supply line.] I must say that my approach has been to consider that provided that the inductor open circuits cleanly (perhaps some smoke, but no fire and no charring of the pcb on which the inductor is mounted) then that is OK safety-wise. Personally, I would not be happy if an inner-layer trace were to burn up for both safety reasons and board re-use reasons. I'm none too keen on surface layers burning up either. A possible safety problem with inner traces opening is that this failure could damage the safety insulation (e.g. by charring or de-lamination) between other traces on that pcb. This of course would vary from board to board and may not have been an issue for Joe's board. Of course, I am also open to flaming but to an extent that's how we all learn. Perhaps some will take issue with me in applying a partial short in addition to a dead short. In my defence I will say that I work for a manufacturer and not a test lab and the reality is that failed capacitors are unlikely to have a zero ohm impedance when they fail in real life. The question then becomes one of how far should one go to minimise product liability? So, having put on my Nomex clothing I await a reply! Richard Hughes -Original Message- In a message dated 11/27/2002, Joe Randolph writes: The only remaining gray area is whether the failure of a component or circuit trace is acceptable *provided* that it is located on the same circuit card where the short was induced, *and* that no safety hazard resulted. My interpretation is that this would be acceptable.
RE: Short circuit tests in GR-1089
Last I heard, and please correct me if not, was that Verizon had rejected the new standards much to the chagrin of the rest of the industry. Gary -Original Message- From: j...@aol.com [mailto:j...@aol.com] Sent: Wednesday, November 27, 2002 1:07 PM To: t...@world.std.com; emc-p...@majordomo.ieee.org Subject: Re: Short circuit tests in GR-1089 Hello All: Many thanks to all who responded to my question about this requirement. Many of the responses were quite interesting and persuasive, even though some of them were directly opposed. I think that the expanded description in the new third edition of GR-1089 helps resolve most of the uncertainty I had with regard to this requirement. I was not aware that the new edition of GR-1089 had been issued, so this discussion was doubly useful. Telcordia has now received some of my $$ for a copy of the new edition. Joe Randolph Telecom Design Consultant Randolph Telecom, Inc. 781-721-2848 http://www.randolph-telecom.com --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list
Re: Short circuit tests in GR-1089
In a message dated 11/27/2002, Marko writes: So what did you decide? Is a fuse blowing acceptable? I'm sure others would be interested as well. Hi Marko: So you want me to go on the record so I can get flamed? OK, here goes: The revised text in Issue 3 of GR-1089 (kindly posted to the group by Alain Servais) explicitly states that fuses are acceptable. The text is not 100% clear on whether the fuse has to be located on the module where the short was induced or whether it can be anywhere in the system, but it appears that the fuse could be anywhere. The only remaining gray area is whether the failure of a component or circuit trace is acceptable *provided* that it is located on the same circuit card where the short was induced, *and* that no safety hazard resulted. My interpretation is that this would be acceptable. This conclusion is based on the following considerations: 1) Issue 3 makes it very clear that failure of something other than a fuse is NOT permitted if it located on a module other than the one where the short was applied. 2) Issue 3 also says that the module where the short was applied does not have to work after the test is over. 3) It seems unreasonable to require a circuit card or module to continue to function after a short was applied on that module. The short itself simulates a fault condition that would require replacement of the module. If so, what's the point of requiring that nothing else on the module is damaged? It doesn't serve any of the reliability goals that are part of the implied intent of the requirement. For the module itself, it would seem that a sufficient criterion would be that no safety hazard occurs. I suspect that others may disagree with this interpretation, and I am open to discussion about it. The fact is that I would be inclined to use fuses at that module level on any new design unless I was VERY sure that the failure mechanism would not create a fire, fragmentation, or electrical safety hazard as stated in GR-1089. In the case that prompted me to post this question in the first place, the failure mode was an open circuit trace, on an inner layer of the circuit card where the short was applied, in an existing product. Under the circumstances, I am not inclined to insist on redesign of that product to retrofit a fuse. However, I would recommend the inclusion of a fuse in any similar product designed in the future. Joe Randolph Telecom Design Consultant Randolph Telecom, Inc. 781-721-2848 http://www.randolph-telecom.com
Re: Short circuit tests in GR-1089
Hello All: Many thanks to all who responded to my question about this requirement. Many of the responses were quite interesting and persuasive, even though some of them were directly opposed. I think that the expanded description in the new third edition of GR-1089 helps resolve most of the uncertainty I had with regard to this requirement. I was not aware that the new edition of GR-1089 had been issued, so this discussion was doubly useful. Telcordia has now received some of my $$ for a copy of the new edition. Joe Randolph Telecom Design Consultant Randolph Telecom, Inc. 781-721-2848 http://www.randolph-telecom.com --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list
RE: Short circuit tests in GR-1089
Hi All, My $.02 worth... I strongly disagree with what has been said regarding operation of output fuses. You may have a case for input fuses/circuit breakers. It is my belief that the purpose of this test, which is a cross referenced follow through to the design requirements now contained in GR-78, is to ensure that the circuit board has been designed to handle fault currents and is reliable. As has come up here before, a dead short is not the maximum fault current that a given power supply will see. It is more likely to be an ohm or two (silicon short) that fails to activate the crowbar circuit and the short should be applied using an adjustable power resistor tweaked to a maximum current reading. You are expected to discover if your PCB surface traces, via plating, and thermal relief (if used) are sized correctly for the maximum current produced by a fault condition. If you have a fuse in-line with the output of your supply, you FAIL the test! The requirement is quite plain: R9-20[92] For both grounded and ungrounded power supplies, conformance to this requirement shall be demonstrated by the absence of damage to equipment, conductors and conductor insulation, and ANY COMPONENT of the fault current path. One will note that it does not say any component except fuses or circuit breakers. To meet this requirement, you will have designed a supply that will not be subjected to failure from incidental short circuits. One may argue that this is not fair, but let us not forget that NEBS is all about reliability. It not only must be safe, but it needs to work in foreseeable misuse environments so we can continue to enjoy that dial tone each and every time we pick up the handset. If one wishes to design, build, and test telecommunications equipment to the standard of excellence defined by NEBS, one must digest the whole family of documents defined as FR-2063, not just the requirements of GR63/GR1089. Have a Great Day, Dave Spencer Two Peppers -Original Message- From: owner-emc-p...@majordomo.ieee.org [mailto:owner-emc-p...@majordomo.ieee.org] On Behalf Of Lou Aiken Sent: Monday, November 25, 2002 10:38 PM To: Ted Rook; j...@aol.com; Subject: Re: Short circuit tests in GR-1089 I'd like to add that the product need not operate correctly after a fault condition causes a fuse to open, it must only remain safe - within the meaning of the standard. Regards, Lou Aiken, LaMer LLC 27109 Palmetto Drive Orange Beach, AL 36561 USA tel ++ 1 251 981 6786 fax ++ 1 251 981 3054 - Original Message - From: Ted Rook t...@crestaudio.com To: j...@aol.com; emc-p...@ieee.org Sent: Monday, November 25, 2002 5:25 PM Subject: Re: Short circuit tests in GR-1089 I'm not an expert on GR1089 but I think that your interpretation should include careful consideration of what constitutes damage. The operation of a fuse or a circuit breaker is not damage. That is normal operation. What the specification is seeking to eliminate is overheating, explosion, loss of insulating properties, improper sizing of conductors and improper sizing of connections, all of which may give rise to damage under short circuit conditions. If the fuse blows and the fuseholder bursts into flames then that is a problem. If the fuse blows and everything fails safe, and normal operation can be restored by replacement of a fuse then no hazardous condition has been created. Does this help? Best Regards Ted Rook, Console Engineering, ext 4659 Please note our new location and phone numbers: Crest Audio Inc, 16-00 Pollitt Drive Fair Lawn, NJ 07410 USA 201 475 4600 telephone receptionist, 8.30 - 5 pm EST. 201 475 4659 direct line w/voice mail, 24 hrs. 201 475 4677 fax, 24 hrs. --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions
Re: Short circuit tests in GR-1089
I'd like to add that the product need not operate correctly after a fault condition causes a fuse to open, it must only remain safe - within the meaning of the standard. Regards, Lou Aiken, LaMer LLC 27109 Palmetto Drive Orange Beach, AL 36561 USA tel ++ 1 251 981 6786 fax ++ 1 251 981 3054 - Original Message - From: Ted Rook t...@crestaudio.com To: j...@aol.com; emc-p...@ieee.org Sent: Monday, November 25, 2002 5:25 PM Subject: Re: Short circuit tests in GR-1089 I'm not an expert on GR1089 but I think that your interpretation should include careful consideration of what constitutes damage. The operation of a fuse or a circuit breaker is not damage. That is normal operation. What the specification is seeking to eliminate is overheating, explosion, loss of insulating properties, improper sizing of conductors and improper sizing of connections, all of which may give rise to damage under short circuit conditions. If the fuse blows and the fuseholder bursts into flames then that is a problem. If the fuse blows and everything fails safe, and normal operation can be restored by replacement of a fuse then no hazardous condition has been created. Does this help? Best Regards Ted Rook, Console Engineering, ext 4659 Please note our new location and phone numbers: Crest Audio Inc, 16-00 Pollitt Drive Fair Lawn, NJ 07410 USA 201 475 4600 telephone receptionist, 8.30 - 5 pm EST. 201 475 4659 direct line w/voice mail, 24 hrs. 201 475 4677 fax, 24 hrs. --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list
Re: Short circuit tests in GR-1089
I'm not an expert on GR1089 but I think that your interpretation should include careful consideration of what constitutes damage. The operation of a fuse or a circuit breaker is not damage. That is normal operation. What the specification is seeking to eliminate is overheating, explosion, loss of insulating properties, improper sizing of conductors and improper sizing of connections, all of which may give rise to damage under short circuit conditions. If the fuse blows and the fuseholder bursts into flames then that is a problem. If the fuse blows and everything fails safe, and normal operation can be restored by replacement of a fuse then no hazardous condition has been created. Does this help? Best Regards Ted Rook, Console Engineering, ext 4659 Please note our new location and phone numbers: Crest Audio Inc, 16-00 Pollitt Drive Fair Lawn, NJ 07410 USA 201 475 4600 telephone receptionist, 8.30 - 5 pm EST. 201 475 4659 direct line w/voice mail, 24 hrs. 201 475 4677 fax, 24 hrs. --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list
Re: Short circuit tests in GR-1089
This was resolved a couple of NEBS conferences ago. All the main RBOCs were present and they agreed that a fuse was a special case. The fuse is designed to open, therefore operation of the fuse is normal and allowed. This may be a semantic strech, but that's where the current NEBS interpretation lies. All other parts of the board must remain undamaged. The no fire hazard is a significant weakening of the general interpretation and probably represents aggressive engineering judgement. Jon. j...@aol.com wrote: Hello All: I am hoping that some of you can help clarify the intent of requirement R9-20 in Telcordia GR-1089. Taken literally, the requirement says that there shall be no damage to equipment, conductors, or components when the DC power supply is shorted at the load. This could even be interpreted to preclude the use of a fuse that has to be replaced. One test lab has told me that as long as no fire hazard is created from this test, it is considered to have been passed. Needless to say, this differs a bit from the literal interpretation. I guess it would help if I had a better feel for the overall goal of the short circuit testing. Any insight on this would be most appreciated. Joe Randolph Telecom Design Consultant Randolph Telecom, Inc. 781-721-2848 http://www.randolph-telecom.com
RE: Short circuit tests in GR-1089
Joe, I was going to suggest that you look into Issue 3 of GR-1089, but you have been given the basics. I would suggest anyone who has to live with this standard, get the new issue and spend a day or so to really look it over in detail. There was a great deal of work put into clarifying intent of these requirements, as well as many others. It should be available from Telcordia now. Jeff Whitmire usual disclaimers - comments are mine but may not be my employers --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list
RE: Short circuit tests in GR-1089
as necessary. Compiled from Issue 3 GR-1089 Alain Servais Compliance Engineer -Original Message- From: j...@aol.com [mailto:j...@aol.com] Sent: Monday, November 25, 2002 1:25 PM To: emc-p...@majordomo.ieee.org; t...@world.std.com Subject:Short circuit tests in GR-1089 File: Short circuit tests in GR-1089.TXT Hello All: I am hoping that some of you can help clarify the intent of requirement R9-20 in Telcordia GR-1089. Taken literally, the requirement says that there shall be no damage to equipment, conductors, or components when the DC power supply is shorted at the load. This could even be interpreted to preclude the use of a fuse that has to be replaced. One test lab has told me that as long as no fire hazard is created from this test, it is considered to have been passed. Needless to say, this differs a bit from the literal interpretation. I guess it would help if I had a better feel for the overall goal of the short circuit testing. Any insight on this would be most appreciated. Joe Randolph Telecom Design Consultant Randolph Telecom, Inc. 781-721-2848 http://www.randolph-telecom.com The information contained in this message may be privileged and confidential and protected from disclosure. If the reader of this message is not the intended recipient, or an employee or agent responsible for delivering this message to the intended recipient, you are hereby notified that any reproduction, dissemination or distribution of this communication is strictly prohibited. If you have received this communication in error, please notify us immediately by replying to the message and deleting it from your computer. Thank you. Tellabs --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list
RE: Short circuit tests in GR-1089
Oops - wrong short circuit test - just realized. Sorry about that. My mind is occupied by that one currently... The on-board short-circuit test is to simulate a short occurring for whatever reason (manufacturing defect, design defect, operational fault). Since something bad happened, in my opinion the card is allowed to fail as long as it fails safe. Opening a fuse is certainly an acceptable method to remove the electrical safety hazard. ...Marko -Original Message- From: Marko Radojicic Sent: Monday, November 25, 2002 11:14 AM To: 'j...@aol.com'; emc-p...@majordomo.ieee.org; t...@world.std.com Subject: RE: Short circuit tests in GR-1089 Joe, The short-circuit test is to simulate the most prevalent source of telecom disruption: the back-hoe. When a buried cable is inadvertently cut, the pairs could short together or to the cable sheath. I really can't see how a test lab can misinterpret the requirement (R4-6 for telecom ports). It clearly states that replacing fuses is not an allowable situation. The EUT shall not be damaged, shall not require manual intervention (such as to reset circuit breaker or replace fuses) to restore service, and shall not become a fire, fragmentation, or electrical safety hazard as a result of the application of a short circuit ... I'm quite sure that whomever you spoke with at the test lab is in error and will probably reconsider their position if they read the standard a little more carefully. Cheers, Marko Marko Radojicic Manager, Compliance and Reliability Turnstone Networks, inc. 2220 Central Expressway Santa Clara, CA 95050 mar...@turnstone.com 408/907-1739 -Original Message- From: j...@aol.com [mailto:j...@aol.com] Sent: Monday, November 25, 2002 10:25 AM To: emc-p...@majordomo.ieee.org; t...@world.std.com Subject: Short circuit tests in GR-1089 Hello All: I am hoping that some of you can help clarify the intent of requirement R9-20 in Telcordia GR-1089. Taken literally, the requirement says that there shall be no damage to equipment, conductors, or components when the DC power supply is shorted at the load. This could even be interpreted to preclude the use of a fuse that has to be replaced. One test lab has told me that as long as no fire hazard is created from this test, it is considered to have been passed. Needless to say, this differs a bit from the literal interpretation. I guess it would help if I had a better feel for the overall goal of the short circuit testing. Any insight on this would be most appreciated. Joe Randolph Telecom Design Consultant Randolph Telecom, Inc. 781-721-2848 http://www.randolph-telecom.com
