Re: [PSES] protective bonding test at 12V
In message 8afe57f0-9f97-40cb-8523-1394ec31e...@yahoo.com, dated Tue, 9 Apr 2013, Peter Merguerian pmerguerian2...@yahoo.com writes: It does not make a difference. I have also seen standards with 6 V mentioned. I also do not think you will get variations in impedance results if you test inject a current of 5 A, 10 A or as I have seen a manufacturer do it at 40A as they mentioned that a Canadian test organization insisted they do it as part of their production-line tests!!! The current value is set by the possibility that a too-small wire or one with broken strands would not carry the fault current. The voltage requirement is (or was traditionally) set so as to break down any surface-layer resistance in metal-to-metal contacts. -- OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk They took me to a specialist burns unit - and made me learn 'To a haggis'. John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to emc-p...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@radiusnorth.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: dhe...@gmail.com
Re: [PSES] protective bonding test at 12V
*From:* Peter Merguerian [mailto:pmerguerian2...@yahoo.com] *Sent:* Tuesday, April 09, 2013 08:23 I also do not think you will get variations in impedance results if you test inject a current of 5 A, 10 A or as I have seen a manufacturer do it at 40A Peter – When performing a 40 A test in my prior labs, I’ve seen the voltage drop across the tested current path change with time, mostly due to heating effects. Less heating necessarily leads to a lesser resistance value, since resistance of any conductor is dependent on its temperature. Peter Tarver This email message is for the sole use of the intended recipient(s) and may contain confidential and/or privileged information. If you are not an intended recipient, you may not review, use, copy, disclose or distribute this message. If you received this message in error, please contact the sender by reply email and destroy all copies of the original message. - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to emc-p...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@radiusnorth.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: dhe...@gmail.com
Re: [PSES] protective bonding test at 12V
It does not make a difference. I have also seen standards with 6 V mentioned. I also do not think you will get variations in impedance results if you test inject a current of 5 A, 10 A or as I have seen a manufacturer do it at 40A as they mentioned that a Canadian test organization insisted they do it as part of their production-line tests!!! Sent from my iPhone Peter S. Merguerian pe...@goglobalcompliance.com Go Global Compliance Inc. www.goglobalcompliance.com (408) 931-3303 On Mar 29, 2013, at 10:08 AM, Jose Moreno jose.mor...@alpha.ca wrote: Hello, According to EN 60950, the resistance of the protective bonding conductor has to be measured with a test voltage not greater then 12V. Does anybody have a clue about the rationale for the 12V requirement? If we measure the current and the voltage drop across the bonding conductor, what difference does it make if we use 12V or 24V? Thanks - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to emc-p...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@radiusnorth.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher j.bac...@ieee.org David Heald dhe...@gmail.com - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to emc-p...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@radiusnorth.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: dhe...@gmail.com
Re: [PSES] protective bonding test at 12V
Kirchhoff's Voltage Law makes it clear that the test results are not affected by the source voltage, if the measured quantity is the voltage drop across the current path through the EUT. There is a personnel safety argument to use a low voltage, but I question whether 12 V should be the high limit for safety. I can say that it's much simpler to drive high current at low voltage for the purposes of this test. For example, using a variable autotransformer on the high voltage side of a step down transformer operated in short-circuit mode. Peter Tarver This email message is for the sole use of the intended recipient(s) and may contain confidential and/or privileged information. If you are not an intended recipient, you may not review, use, copy, disclose or distribute this message. If you received this message in error, please contact the sender by reply email and destroy all copies of the original message. - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to emc-p...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@radiusnorth.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: dhe...@gmail.com
Re: [PSES] protective bonding test at 12V
In message 51562712.8020...@ieee.org, dated Fri, 29 Mar 2013, Richard Nute ri...@ieee.org writes: If the circuit is open, then, I suppose, I could apply a high enough voltage to cause a breakdown at the point where the circuit is open. The voltage would need to be more than 323 volts as air does not break down below that voltage (Paschen's Law). The putative bad contact is not an air-gap but an oxide layer. Ps you know, the breakdown voltage of such layers is quite low (as in copper-oxide rectifiers), but is several volts. If I remember correctly, the applied voltage was limited to 6 V in a former edition of BS 415, long before it was fully aligned with IEC 65. We actually see this effect in some types of switch; there is a range of European mains switches that is well-known for not working reliably at 12 V or less. It was also an issue in push-button switches used for function selection in radios, etc. of the 1960s-1980s. -- OOO - Own Opinions Only. See www.jmwa.demon.co.uk Which Thunderbird will David Miliband pilot? Or will he drive Lady Penelope? John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to emc-p...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@radiusnorth.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: dhe...@gmail.com
Re: [PSES] protective bonding test at 12V
In message 01902c6130f65c4e82278e13908155c62adff...@exchange.alpha.ca, dated Fri, 29 Mar 2013, Jose Moreno jose.mor...@alpha.ca writes: If we measure the current and the voltage drop across the bonding conductor, what difference does it make if we use 12V or 24V? At the higher voltage, a bad contact could be 'broken down' by microwelding and give a spurious low resistance reading. -- OOO - Own Opinions Only. See www.jmwa.demon.co.uk Which Thunderbird will David Miliband pilot? Or will he drive Lady Penelope? John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to emc-p...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@radiusnorth.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: dhe...@gmail.com
Re: [PSES] protective bonding test at 12V
Hi Jose: The voltage of the test generator is of no consequence. The test is performed at 30 amps (for a 15-amp mains) into a resistance not exceeding 0.1 ohm. According to Ohm's Law, the voltage across the 0.1 ohm resistor is 3 volts. On the other hand, if the potential is 12 volts and the current is 30 amps, then the resistance is 0.4 ohms. The requirement is for 0.1 ohm or less at 200% of the rating of the overcurrent device. The generator will never get to 12 volts (or 24 volts) during the test if the equipment meets the 0.1 ohm, 200% requirement. I don't know why the standard specifies the the voltage of the test source. But, if you are a certification house, then the test equipment cannot exceed 12 volts (although I don't know how one would confirm this except under open-circuit conditions, which has no effect on the measurement). With best regards, Rich On 3/29/2013 10:08 AM, Jose Moreno wrote: Hello, According to EN 60950, the resistance of the protective bonding conductor has to be measured with a test voltage *not greater then 12V*. Does anybody have a clue about the rationale for the 12V requirement? If we measure the current and the voltage drop across the bonding conductor, what difference does it make if we use 12V or 24V? Thanks - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to emc-p...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@radiusnorth.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: dhe...@gmail.com
Re: [PSES] protective bonding test at 12V
In message 5155f037.6080...@ieee.org, dated Fri, 29 Mar 2013, Richard Nute ri...@ieee.org writes: The voltage of the test generator is of no consequence. Well, that isn't what my ancestors told me, which is what I recited. -- OOO - Own Opinions Only. See www.jmwa.demon.co.uk Which Thunderbird will David Miliband pilot? Or will he drive Lady Penelope? John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to emc-p...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@radiusnorth.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: dhe...@gmail.com
Re: [PSES] protective bonding test at 12V
Hi Ken and John: Let me see if I understand this correctly. The test goes like this. We're testing a bonding conductor, so I assume that, at least, the resistance at low current (with an ohmmeter) is near zero. The objective is to determine that the bonding conductor can carry sufficent fault current such that the overcurrent device can open the circuit. If the conductors are too small, the resistance may be too high, and the fault current too low, such that the overcurrent device will not operate. Therefore, the resistance of bonding conductor must be determined at the worst-case overcurrent device operating current (taken as 200%) and operating time (taken as 2 minutes). So, I hook up the test equipment to both ends of the conductor. Then, I gradually turn up the test current (and voltage) towards 30 amps. Assume the resistance is 0.1 ohm. As I increase the current to 1 amp, I get 0.1 volt. Then, 2 amps and 0.2 volts. And so forth until I get 30 amps and 3 volts. I never get to 12 volts. The EUT passes. Now, let's assume a connection is contaminated and the resistance is 1 ohm. I gradually turn up the test current (and voltage). At 1 amp, I get 1 volt. At 2 amps, I get 2 volts. If the test equipment is limited to 12 volts per the standard, then I get 12 amps and 12 volts. I can't get to 30 amps, and the EUT fails the test. Even if I could get to 30 amps and 30 volts, the EUT fails the test. If the circuit is open, then I can't get any current at any voltage. The EUT fails the test. If the circuit is open, then, I suppose, I could apply a high enough voltage to cause a breakdown at the point where the circuit is open. The voltage would need to be more than 323 volts as air does not break down below that voltage (Paschen's Law). Low-voltage arcing is due to physical opening of a contact, where the contact area reduces as the contact approaches the break of connection. When the contact area reduces, the current density increases to the point where the metal melts and then sprays away due to the EMF in the molten conductor. Then, the combination of the molten metal and the current density superheats the surrounding air to the point where the air breaks down due to the heat and a visible arc (in air) occurs. This is not a function of the voltage across the contact, but the current through the contact. Of course, if the physical motion re-makes the contact before the molten metal has solidified, then the contact may very well be micro-welded. In which case, the contact may very well pass the 30-amp test, depending on the heat-sinking of the assembly. I've tested loose connections at 25 amps. I moved the loose connection for both break and make. It the parts which are loose are relatively massive, they provide a heat-sink at the point of connection, and the loose connection will easily pass the test. This is my understanding of the physical phenomenon involved in the test. I still don't see the effect of voltage on the test. HELP! Best regards, Rich On 3/29/2013 1:55 PM, Ken Javor wrote: My ancestors informed me similarly. Corrosion, grease, any thin non-conductive layer between the part to be grounded and ground is invisible to a high potential, but detectable by a lower potential that cannot punch through it. Ken Javor Phone: (256) 650-5261 From: John Woodgate j...@jmwa.demon.co.uk Date: Fri, 29 Mar 2013 20:20:30 + To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: protective bonding test at 12V In message 5155f037.6080...@ieee.org, dated Fri, 29 Mar 2013, Richard Nute ri...@ieee.org writes: The voltage of the test generator is of no consequence. Well, that isn't what my ancestors told me, which is what I recited. -- OOO - Own Opinions Only. See www.jmwa.demon.co.uk Which Thunderbird will David Miliband pilot? Or will he drive Lady Penelope? John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to emc-p...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@radiusnorth.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: dhe...@gmail.com
Re: [PSES] protective bonding test at 12V
I'll take a stab at this and then Mr. Woodgate can individually. Due to the time difference, he made the first response on this, and his response was precisely what mine would have been, but he got up earlier than I did. Due to the time difference again, I'm up later than he is. First, I don't know the particulars of your standard and test method. All I was saying is that if there was corrosion, or paint, or any sort of non-conductive material in series with the ground path to be measured, a low potential could see that as an open, but a high potential would arc across it. So my point was that if you tested the bond at a high potential, you would not catch the fqct that there was some sort of gunk gumming up the works, to use a technical term. This is not a linear function, as per your example below. To use your numbers, the low potentials would see an open, or nearly so, but above some threshold applied potential, the bond path would suddenly drop from very high to your 0.1 Ohm target value. Ken Javor Phone: (256) 650-5261 From: Richard Nute ri...@ieee.org Reply-To: ri...@ieee.org Date: Fri, 29 Mar 2013 16:43:14 -0700 To: Ken Javor ken.ja...@emccompliance.com, John Woodgate j...@jmwa.demon.co.uk Cc: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: protective bonding test at 12V Hi Ken and John: Let me see if I understand this correctly. The test goes like this. We're testing a bonding conductor, so I assume that, at least, the resistance at low current (with an ohmmeter) is near zero. The objective is to determine that the bonding conductor can carry sufficent fault current such that the overcurrent device can open the circuit. If the conductors are too small, the resistance may be too high, and the fault current too low, such that the overcurrent device will not operate. Therefore, the resistance of bonding conductor must be determined at the worst-case overcurrent device operating current (taken as 200%) and operating time (taken as 2 minutes). So, I hook up the test equipment to both ends of the conductor. Then, I gradually turn up the test current (and voltage) towards 30 amps. Assume the resistance is 0.1 ohm. As I increase the current to 1 amp, I get 0.1 volt. Then, 2 amps and 0.2 volts. And so forth until I get 30 amps and 3 volts. I never get to 12 volts. The EUT passes. Now, let's assume a connection is contaminated and the resistance is 1 ohm. I gradually turn up the test current (and voltage). At 1 amp, I get 1 volt. At 2 amps, I get 2 volts. If the test equipment is limited to 12 volts per the standard, then I get 12 amps and 12 volts. I can't get to 30 amps, and the EUT fails the test. Even if I could get to 30 amps and 30 volts, the EUT fails the test. If the circuit is open, then I can't get any current at any voltage. The EUT fails the test. If the circuit is open, then, I suppose, I could apply a high enough voltage to cause a breakdown at the point where the circuit is open. The voltage would need to be more than 323 volts as air does not break down below that voltage (Paschen's Law). Low-voltage arcing is due to physical opening of a contact, where the contact area reduces as the contact approaches the break of connection. When the contact area reduces, the current density increases to the point where the metal melts and then sprays away due to the EMF in the molten conductor. Then, the combination of the molten metal and the current density superheats the surrounding air to the point where the air breaks down due to the heat and a visible arc (in air) occurs. This is not a function of the voltage across the contact, but the current through the contact. Of course, if the physical motion re-makes the contact before the molten metal has solidified, then the contact may very well be micro-welded. In which case, the contact may very well pass the 30-amp test, depending on the heat-sinking of the assembly. I've tested loose connections at 25 amps. I moved the loose connection for both break and make. It the parts which are loose are relatively massive, they provide a heat-sink at the point of connection, and the loose connection will easily pass the test. This is my understanding of the physical phenomenon involved in the test. I still don't see the effect of voltage on the test. HELP! Best regards, Rich On 3/29/2013 1:55 PM, Ken Javor wrote: My ancestors informed me similarly. Corrosion, grease, any thin non-conductive layer between the part to be grounded and ground is invisible to a high potential, but detectable by a lower potential that cannot punch through it. Ken Javor Phone: (256) 650-5261 From: John Woodgate j...@jmwa.demon.co.uk Date: Fri, 29 Mar 2013 20:20:30 + To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: protective bonding test at 12V In message 5155f037.6080...@ieee.org, dated Fri, 29 Mar 2013, Richard Nute ri...@ieee.org
