Re: [PSES] Single Point Grounding - Not Achievable at High Frequencies (greater than a few MHz)
Yes, it is! In RF technology it is very common to use a plane as a single grounding point. It is a very satisfying replacement for the single-grounding-point solution. The ground layer in any multi-layer PCB is such a single-plane-ground, with similar electrical properties to the old school single ground concept at both RF and AF frequencies. I would re-formulate the statement in that it is impossible to connect 2 ground points , planes or structures using a single wire/connection. Both Doug and Bill are also right of course from their point of concept/view. Regards, Ing. Gert Gremmen, BSc g.grem...@cetest.nl mailto:g.grem...@cetest.nl www.cetest.nl Kiotoweg 363 3047 BG Rotterdam T 31(0)104152426 F 31(0)104154953 Before printing, think about the environment. Van: emc-p...@ieee.org [mailto:emc-p...@ieee.org] Namens Bill Owsley Verzonden: Tuesday, May 21, 2013 5:02 AM Aan: d...@dsmith.org; Si-List; emc-pstc Onderwerp: Re: Single Point Grounding - Not Achievable at High Frequencies (greater than a few MHz) Dr. Tom Van Doren demonstrates that single point grounding is not possible above the audio frequencies. Thus the lower cutoff in the regulations of 9 kHz. And that is really old school... From: Doug Smith d...@emcesd.com To: Si-List si-l...@freelists.org; emc-pstc emc-p...@ieee.org Sent: Tuesday, April 10, 2012 8:05 PM Subject: Single Point Grounding - Not Achievable at High Frequencies (greater than a few MHz) Hi All, I have just uploaded the first Technical Tidbit article from my new office in Boulder City, NV! Here it is: Technical Tidbit - April 2012 Single Point Grounding - Not Achievable at High Frequencies (greater than a few MHz) The link to the article is: http://emcesd.com/tt2012/tt041012.htm My new office in Boulder City, NV is officially open!!! Still more work to do on the house move so the next few weeks will be very busy and the May Technical Tidbit may be a little late as well. Once the move is complete, I expect to do morning 5 to 10 minute podcasts on technical topics every morning I am in the office. These podcasts will appear on the home page of http://CircuitAdvisor.com http://circuitadvisor.com/ by late morning each day except for days when I am not in the office. Doug -- --- ___ _ Doug Smith \ / ) P.O. Box 60941 = Boulder City, NV 89006-0941 _ / \ / \ _ TEL/FAX: 702-570-6108/570-6013 / /\ \ ] / /\ \ Mobile: 408-858-4528 | q-( ) | o |Email: d...@dsmith.org \ _ /]\ _ / Website: http://www.dsmith.org http://www.dsmith.org/ --- - 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] Single Point Grounding - Not Achievable at High Frequencies (greater than a few MHz)
In message 1369105334.30674.yahoomail...@web160401.mail.bf1.yahoo.com, dated Mon, 20 May 2013, Bill Owsley wdows...@yahoo.com writes: Dr. Tom Van Doren demonstrates that single point grounding is not possible above the audio frequencies. Thus the lower cutoff in the regulations of 9 kHz. And that is really old school... The 'goodness' of single-point grounding is not a function of frequency alone. Circuit impedances are also involved, and this makes the issue so complex that no general rule is possible. Each single point has to be evaluated to determine the acceptability of the impedance between each point to be grounded and the single point and the impedances between the single point and every other single point in the assembly. The latter control the transfer of voltages or currents from one point to be grounded and others connected to the same single point, and between single points. The buzz-word is 'ground bounce' but it's not confined to digital circuits; ground bounce in analogue circuits is (normally) less abrupt but still present. -- OOO - Own Opinions Only. See www.jmwa.demon.co.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] Single Point Grounding - Not Achievable at High Frequencies (greater than a few MHz)
In message FCA549BE3ECF9D4CB8CB8576837EA489140EBF@ZEUS.cetest.local, dated Tue, 21 May 2013, ce-test, qualified testing bv - Gert Gremmen g.grem...@cetest.nl writes: In RF technology it is very common to use a plane as a single grounding point. It isn't a single point; it may be a close approach to a single point but I have seen trouble even at audio frequencies caused by poor layout, due to assuming a ground plane has zero impedance. Distorted current from a Class AB output stage was getting back into an input circuit via the voltage drop between an output device grounding point and an input device grounding point. The problem was discovered because one channel had eight times the THD of the other. -- OOO - Own Opinions Only. See www.jmwa.demon.co.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] safety 60950 and surge suppression circuits
Rich, Given your rational that surge protective components (SPCs), such as MOVs or GDTs, can have a fault mode anywhere between a short-circuit and an open-circuit, looks like there is a disconnect in the test levels. In the open-circuit situation, the SPC does not divert current and the full voltage is applied to the electrical insulation. That being the case and as TC 108 specifies MOVs are tested with a impulse generator voltage of 6 kV peak, why isn't the insulation tested with this 6 kV impulse? Regards Mick. On 20/05/2013 22:50, Richard Nute wrote: Hi Joe: Very quickly... SPDs are not considered reliable components or assemblies. The safety standards anticipate a failure -- anywhere from open-circuit to short-circuit. In the event of an open-circuit, there is no indication of such a failure. And, of course, all transients then pass through the open SPD. Consequently, the equipment safety insulations will be called upon to withstand the expected transient overvoltages. So, the standards require performing the voltage withstand test without the SPD in place. Best regards, Rich On 5/20/2013 1:40 PM, Joe Randolph wrote: Hi Rich: I'm hoping that you can provide one of your straightforward Rich Nute Explanations for the apparent contradiction behind the rationale that allows a surge protection component to be placed across a required safety isolation barrier, and then removed for the purpose of performing the hipot test. I have been involved with safety compliance for over 30 years, and this concept is one that has never made complete sense to me. On one level, I can just bump along and limit my attention to what the safety standard actually says, but I would like to understand what the thinking is behind that. This allowance (removing surge protection components for the hipot test) appears in a variety of standards and clauses within those standards, such as EN 60950-1, clauses 5.2.2, 6.1.2, and 6.2.2. If you could help clarify the thinking behind this allowance, I would greatly appreciate it. Thanks, Joe Randolph Telecom Design Consultant Randolph Telecom, Inc. 781-721-2848 (USA) j...@randolph-telecom.com http://www.randolph-telecom.com http://www.randolph-telecom.com/ Hi Bill: SPDs, regardless of configuration, are notorious for being prone to failure, either short-circuit or open-circuit or any value of resistance between those two extremes. (One cannot predict the energy the SPD will be required to dissipate.) From a safety point of view, all such failures must be accounted for such that the safety of the equipment is not compromised by any failure of the SPD. If the SPD should fail open-circuit, then expected transients that are therefore not attenuated, must not cause the insulation to fail. Hence, the insulation must pass the hi-pot test without the SPD in place. As for the requirement for the GDT to pass the hi-pot test... ??? I don't have any rationale for this. Best regards, Rich On 5/10/2013 10:11 AM, Bill Owsley wrote: I'm running into a dilemma. Not being a Safety Engineer myself, but rubbing elbows with them... On a piece of ITE equipment, I need some surge suppression for worldwide markets with one annoying requirement for 4 kV, otherwise just 2 kV line to earth, and using either plugable cords or permanent connection, whichever is worse. Now the Safety guys tell me that MOV's alone cannot bridge the insulation (Basic or Functional, I forget.) between primary and earth, when using one of power cable options mentioned above. But a proper qualified (GDT) gas discharge tube can do the bridging. So we figured to use them in series. On a quick and dirty bench test it works to 4 kV. Then the Safety guys pull out the rest of the story and point out 5.2.2 which seems to indicate that the GDT is to meet the Hi-Pot test, 1500 vac. Previously, section, 1.5.9.4 (?) indicates that the surge protection devices can be removed during the Hi-Pot test. But now I have a Surge suppression circuit that has to withstand the same Hi-Pot as the rest of the board. Question is how does a surge protection circuit protect the board when it has to meet the same Hi-Pot test? In other words, when a surge comes along, which is going to break over first? The surge protection or the board? Is the purpose of surge suppression is to keep the clamped voltage below a problem level? What am I missing in this? Thanks... - Bill - 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 mailto: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
[PSES] Capacitor Discharge Test IEC 61010-1
What we call the Capacitor Discharge Test in the IEC 61010-1 standard section 6.10.3 says that voltage across the pins of the power cord must not be Hazardous Live 5 seconds after disconnection from the supply. Most labs simply check to see if the voltage across the pins are 60 volts or less at 5 seconds, but the pass/fail criteria is the capacitive charge level described in 6.3.1 c) which is 45uC. 6.3.1 c) points you to Line A of Figure 3 but this chart seems to start at 100 volts. So how do I apply this chart if my 5 second voltage is 80 volts? Am I looking at this wrong or should this chart go down to at least 60 volts? Is there a formula that can be used instead of the chart? In our specific case, we are measuring the discharge of an RF line filter which has 4.4uF of capacitance across the line and the 5 second voltage is 80 volts. My guess would be this filter fails as-is without and additional bleeder resistor but when I discuss it with the company they pick apart the standard and the chart at figure 3. Another question. When you perform this test what line voltage do you use? The highest nominal voltage or do you include +10%? For 230VAC equipment do you test at 230Vrms or 264Vrms (373Vpk)? Thanks to all for any input. The Other Brian LECO Corporation Notice: This communication may contain confidential information intended for the named recipient(s) only. If you received this by mistake, please destroy it and notify us of the error. Thank you. - 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] safety 60950 and surge suppression circuits
Hi Rich: The apparent contradiction that I was trying to describe can be summarized as follows: a) The safety insulation barrier must withstand a hipot test of, say, 1500 VRMS b) It is permissible to bridge this safety insulation barrier with a SPD that breaks down at, say, 300 VRMS In other words, in normal use, the safety insulation barrier can be bypassed by a SPD. For the seemingly artificial circumstances of the hipot test, the SPD can be removed in order to demonstrate compliance with the 1500 VRMS requirement. The 1500 VRMS safety isolation barrier would appear to be relatively useless if, in normal use, it is bridged by a 300 VRMS SPD. In the above example, I avoided specific reference to particular clauses in 60950-1, because I wanted to illustrate the basic scenario that seems to recur in a variety of places, but with differing details. In 60950-1, this scenario seems to appear in clauses 5.2.2, 6.1.2, and 6.2. It also appears in TIA-968 for equipment connected to the telecom network. Joe Randolph Telecom Design Consultant Randolph Telecom, Inc. 781-721-2848 (USA) j...@randolph-telecom.com http://www.randolph-telecom.com Hi Joe: Very quickly... SPDs are not considered reliable components or assemblies. The safety standards anticipate a failure -- anywhere from open-circuit to short-circuit. In the event of an open-circuit, there is no indication of such a failure. And, of course, all transients then pass through the open SPD. Consequently, the equipment safety insulations will be called upon to withstand the expected transient overvoltages. So, the standards require performing the voltage withstand test without the SPD in place. Best regards, Rich On 5/20/2013 1:40 PM, Joe Randolph wrote: Hi Rich: I'm hoping that you can provide one of your straightforward Rich Nute Explanations for the apparent contradiction behind the rationale that allows a surge protection component to be placed across a required safety isolation barrier, and then removed for the purpose of performing the hipot test. I have been involved with safety compliance for over 30 years, and this concept is one that has never made complete sense to me. On one level, I can just bump along and limit my attention to what the safety standard actually says, but I would like to understand what the thinking is behind that. This allowance (removing surge protection components for the hipot test) appears in a variety of standards and clauses within those standards, such as EN 60950-1, clauses 5.2.2, 6.1.2, and 6.2.2. If you could help clarify the thinking behind this allowance, I would greatly appreciate it. Thanks, Joe Randolph Telecom Design Consultant Randolph Telecom, Inc. 781-721-2848 (USA) j...@randolph-telecom.com http://www.randolph-telecom.com http://www.randolph-telecom.com/ Hi Bill: SPDs, regardless of configuration, are notorious for being prone to failure, either short-circuit or open-circuit or any value of resistance between those two extremes. (One cannot predict the energy the SPD will be required to dissipate.) From a safety point of view, all such failures must be accounted for such that the safety of the equipment is not compromised by any failure of the SPD. If the SPD should fail open-circuit, then expected transients that are therefore not attenuated, must not cause the insulation to fail. Hence, the insulation must pass the hi-pot test without the SPD in place. As for the requirement for the GDT to pass the hi-pot test... ??? I don't have any rationale for this. Best regards, Rich On 5/10/2013 10:11 AM, Bill Owsley wrote: I'm running into a dilemma. Not being a Safety Engineer myself, but rubbing elbows with them... On a piece of ITE equipment, I need some surge suppression for worldwide markets with one annoying requirement for 4 kV, otherwise just 2 kV line to earth, and using either plugable cords or permanent connection, whichever is worse. Now the Safety guys tell me that MOV's alone cannot bridge the insulation (Basic or Functional, I forget.) between primary and earth, when using one of power cable options mentioned above. But a proper qualified (GDT) gas discharge tube can do the bridging. So we figured to use them in series. On a quick and dirty bench test it works to 4 kV. Then the Safety guys pull out the rest of the story and point out 5.2.2 which seems to indicate that the GDT is to meet the Hi-Pot test, 1500 vac. Previously, section, 1.5.9.4 (?) indicates that the surge protection devices can be removed during the Hi-Pot test. But now I have a Surge suppression circuit that has to withstand the same Hi-Pot as the rest of the board. Question is how does a surge protection circuit protect the board when it has to meet the same Hi-Pot test? In other words, when a surge comes along, which is going to break over first? The surge protection or the board? Is the purpose of surge suppression is to keep the clamped voltage below a problem level? What am I missing in this? Thanks... - Bill -
Re: [PSES] safety 60950 and surge suppression circuits
Rich - Notwithstanding your statements about the safety insulation needing to meet the testing, I have always viewed the testing with the SPC removed or disabled to be an allowance, since in almost every instance, will cause a false indication of breakdown of the safety insulation by means of fulfilling their intended functions. This view is similar in concept to allowing a dc test when capacitances will allow excess currents to flow during the same tests. Your answer sells better in committee. Peter Tarver -Original Message- From: Richard Nute Hi Joe: Very quickly... SPDs are not considered reliable components or assemblies. The safety standards anticipate a failure -- anywhere from open-circuit to short-circuit. In the event of an open-circuit, there is no indication of such a failure. And, of course, all transients then pass through the open SPD. Consequently, the equipment safety insulations will be called upon to withstand the expected transient overvoltages. So, the standards require performing the voltage withstand test without the SPD in place. Best regards, Rich 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] safety 60950 and surge suppression circuits
Throwing in my 2 cents: Hipot test values are based on expected transients. The concern with the transient overvoltages is that they could punch through insulation needed for safety and subsequently hazardous voltages can be allowed to reach areas where they should not. The function of an SPD is to limit the level of transient overvoltages that propagate through the equipment. If the SPD functions correctly, the insulation should not be stressed by the transients since the SPD shunts the surge current to ground. In other words, the function of the SPD makes it different from the other insulation barriers. While the other barriers must withstand the transient overvoltages, the SPD functions to limit them. Because of the difference in function, it is appropriate to test them differently, or to treat them differently during test. As Rich stated, an SPD may not be reliable in its function to limit the transient overvoltages (for example SPDs are often themselves protected by fusing which then leaves the SPD function inoperable if the fuse opens), so it is appropriate to test the rest of the insulation as if the SPD were not present. Scott Aldous Compliance Manager/Engineering Lab Manager AE Solar Energy +1.970.492.2065 Direct +1.970.407.5872 Fax +1.541.312.3832 Main scott.ald...@aei.com 1625 Sharp Point Drive Fort Collins, CO 80525 www.advanced-energy.com/solarenergyhttp://www.advanced-energy.com/solarenergy From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf Of Joe Randolph Sent: Tuesday, May 21, 2013 3:41 PM To: ri...@ieee.org Cc: Bill Owsley; EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: safety 60950 and surge suppression circuits Hi Rich: The apparent contradiction that I was trying to describe can be summarized as follows: a) The safety insulation barrier must withstand a hipot test of, say, 1500 VRMS b) It is permissible to bridge this safety insulation barrier with a SPD that breaks down at, say, 300 VRMS In other words, in normal use, the safety insulation barrier can be bypassed by a SPD. For the seemingly artificial circumstances of the hipot test, the SPD can be removed in order to demonstrate compliance with the 1500 VRMS requirement. The 1500 VRMS safety isolation barrier would appear to be relatively useless if, in normal use, it is bridged by a 300 VRMS SPD. In the above example, I avoided specific reference to particular clauses in 60950-1, because I wanted to illustrate the basic scenario that seems to recur in a variety of places, but with differing details. In 60950-1, this scenario seems to appear in clauses 5.2.2, 6.1.2, and 6.2. It also appears in TIA-968 for equipment connected to the telecom network. Joe Randolph Telecom Design Consultant Randolph Telecom, Inc. 781-721-2848 (USA) j...@randolph-telecom.com http://www.randolph-telecom.comhttp://www.randolph-telecom.com/ Hi Joe: Very quickly... SPDs are not considered reliable components or assemblies. The safety standards anticipate a failure -- anywhere from open-circuit to short-circuit. In the event of an open-circuit, there is no indication of such a failure. And, of course, all transients then pass through the open SPD. Consequently, the equipment safety insulations will be called upon to withstand the expected transient overvoltages. So, the standards require performing the voltage withstand test without the SPD in place. Best regards, Rich On 5/20/2013 1:40 PM, Joe Randolph wrote: Hi Rich: I'm hoping that you can provide one of your straightforward Rich Nute Explanations for the apparent contradiction behind the rationale that allows a surge protection component to be placed across a required safety isolation barrier, and then removed for the purpose of performing the hipot test. I have been involved with safety compliance for over 30 years, and this concept is one that has never made complete sense to me. On one level, I can just bump along and limit my attention to what the safety standard actually says, but I would like to understand what the thinking is behind that. This allowance (removing surge protection components for the hipot test) appears in a variety of standards and clauses within those standards, such as EN 60950-1, clauses 5.2.2, 6.1.2, and 6.2.2. If you could help clarify the thinking behind this allowance, I would greatly appreciate it. Thanks, Joe Randolph Telecom Design Consultant Randolph Telecom, Inc. 781-721-2848 (USA) j...@randolph-telecom.com http://www.randolph-telecom.comhttp://www.randolph-telecom.com/ http://www.randolph-telecom.com/ Hi Bill: SPDs, regardless of configuration, are notorious for being prone to failure, either short-circuit or open-circuit or any value of resistance between those two extremes. (One cannot predict the energy the SPD will be required to dissipate.) From a safety point of view, all such failures must be accounted for such that the safety of the equipment is not compromised
Re: [PSES] safety 60950 and surge suppression circuits
Hi Scott: Your explanation makes sense but it presumes the SPD shunts the current to ground. It would appear to me that the SPD is allowed to simply bridge the isolation barrier. That is the aspect that seems contradictory to me. In 60950-1 clauses 6.1.2 and 6.2 (the ones I work with most frequently) there is no explicit requirement that the SPD be connected to a reliable ground. Rather, it is simply allowed to bridge the isolation barrier. Based on quick read of clause 5.2.2, the situation would appear to be similar there as well. Joe Randolph Telecom Design Consultant Randolph Telecom, Inc. 781-721-2848 (USA) j...@randolph-telecom.com http://www.randolph-telecom.com Throwing in my 2 cents: Hipot test values are based on expected transients. The concern with the transient overvoltages is that they could punch through insulation needed for safety and subsequently hazardous voltages can be allowed to reach areas where they should not. The function of an SPD is to limit the level of transient overvoltages that propagate through the equipment. If the SPD functions correctly, the insulation should not be stressed by the transients since the SPD shunts the surge current to ground. In other words, the function of the SPD makes it different from the other insulation barriers. While the other barriers must withstand the transient overvoltages, the SPD functions to limit them. Because of the difference in function, it is appropriate to test them differently, or to treat them differently during test. As Rich stated, an SPD may not be reliable in its function to limit the transient overvoltages (for example SPDs are often themselves protected by fusing which then leaves the SPD function inoperable if the fuse opens), so it is appropriate to test the rest of the insulation as if the SPD were not present. Scott Aldous Compliance Manager/Engineering Lab Manager AE Solar Energy +1.970.492.2065 Direct +1.970.407.5872 Fax +1.541.312.3832 Main scott.ald...@aei.com 1625 Sharp Point Drive Fort Collins, CO 80525 www.advanced-energy.com/solarenergy From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf Of Joe Randolph Sent: Tuesday, May 21, 2013 3:41 PM To: ri...@ieee.org Cc: Bill Owsley; EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: safety 60950 and surge suppression circuits Hi Rich: The apparent contradiction that I was trying to describe can be summarized as follows: a) The safety insulation barrier must withstand a hipot test of, say, 1500 VRMS b) It is permissible to bridge this safety insulation barrier with a SPD that breaks down at, say, 300 VRMS In other words, in normal use, the safety insulation barrier can be bypassed by a SPD. For the seemingly artificial circumstances of the hipot test, the SPD can be removed in order to demonstrate compliance with the 1500 VRMS requirement. The 1500 VRMS safety isolation barrier would appear to be relatively useless if, in normal use, it is bridged by a 300 VRMS SPD. In the above example, I avoided specific reference to particular clauses in 60950-1, because I wanted to illustrate the basic scenario that seems to recur in a variety of places, but with differing details. In 60950-1, this scenario seems to appear in clauses 5.2.2, 6.1.2, and 6.2. It also appears in TIA-968 for equipment connected to the telecom network. Joe Randolph Telecom Design Consultant Randolph Telecom, Inc. 781-721-2848 (USA) j...@randolph-telecom.com http://www.randolph-telecom.com Hi Joe: Very quickly... SPDs are not considered reliable components or assemblies. The safety standards anticipate a failure -- anywhere from open-circuit to short-circuit. In the event of an open-circuit, there is no indication of such a failure. And, of course, all transients then pass through the open SPD. Consequently, the equipment safety insulations will be called upon to withstand the expected transient overvoltages. So, the standards require performing the voltage withstand test without the SPD in place. Best regards, Rich On 5/20/2013 1:40 PM, Joe Randolph wrote: Hi Rich: I'm hoping that you can provide one of your straightforward Rich Nute Explanations for the apparent contradiction behind the rationale that allows a surge protection component to be placed across a required safety isolation barrier, and then removed for the purpose of performing the hipot test. I have been involved with safety compliance for over 30 years, and this concept is one that has never made complete sense to me. On one level, I can just bump along and limit my attention to what the safety standard actually says, but I would like to understand what the thinking is behind that. This allowance (removing surge protection components for the hipot test) appears in a variety of standards and clauses within those standards, such as EN 60950-1, clauses 5.2.2, 6.1.2, and 6.2.2. If you could help clarify the thinking behind this allowance, I would greatly appreciate it. Thanks, Joe Randolph Telecom Design Consultant Randolph
Re: [PSES] Single Point Grounding - Not Achievable at High Frequencies (greater than a few MHz)
dang you beat me too it. I thought this would evolve over several notes, but no... you had to go all the way at once. I was going to go from single point, expanded to a single edge, expended to a plane, which can again be expanded to a chassis, and with care on cable shield terminations, to single ground set of chassis, and then stepped up the CBN, common bonding network of a single ground room. Now to go see everyone else says! From: ce-test, qualified testing bv - Gert Gremmen g.grem...@cetest.nl To: Bill Owsley wdows...@yahoo.com; d...@dsmith.org; Si-List si-l...@freelists.org; emc-pstc emc-p...@ieee.org Sent: Tuesday, May 21, 2013 2:40 AM Subject: RE: Single Point Grounding - Not Achievable at High Frequencies (greater than a few MHz) Yes, it is….! In RF technology it is very common to use a plane as a single grounding point. It is a very satisfying replacement for the single-grounding-point solution. The ground layer in any multi-layer PCB is such a single-plane-ground, with similar electrical properties to the “old school” single ground concept at both RF and AF frequencies. I would re-formulate the statement in that it is impossible to connect 2 ground points , planes or structures using a single wire/connection. Both Doug and Bill are also right of course from their point of concept/view. Regards, Ing. Gert Gremmen, BSc g.grem...@cetest.nl www.cetest.nl Kiotoweg 363 3047 BG Rotterdam T 31(0)104152426 F 31(0)104154953 Before printing, think about the environment. Van:emc-p...@ieee.org [mailto:emc-p...@ieee.org] Namens Bill Owsley Verzonden: Tuesday, May 21, 2013 5:02 AM Aan: d...@dsmith.org; Si-List; emc-pstc Onderwerp: Re: Single Point Grounding - Not Achievable at High Frequencies (greater than a few MHz) Dr. Tom Van Doren demonstrates that single point grounding is not possible above the audio frequencies. Thus the lower cutoff in the regulations of 9 kHz. And that is really old school... From:Doug Smith d...@emcesd.com To: Si-List si-l...@freelists.org; emc-pstc emc-p...@ieee.org Sent: Tuesday, April 10, 2012 8:05 PM Subject: Single Point Grounding - Not Achievable at High Frequencies (greater than a few MHz) Hi All, I have just uploaded the first Technical Tidbit article from my new office in Boulder City, NV! Here it is: Technical Tidbit - April 2012 Single Point Grounding - Not Achievable at High Frequencies (greater than a few MHz) The link to the article is: http://emcesd.com/tt2012/tt041012.htm My new office in Boulder City, NV is officially open!!! Still more work to do on the house move so the next few weeks will be very busy and the May Technical Tidbit may be a little late as well. Once the move is complete, I expect to do morning 5 to 10 minute podcasts on technical topics every morning I am in the office. These podcasts will appear on the home page of http://CircuitAdvisor.com by late morning each day except for days when I am not in the office. Doug -- --- ___ _ Doug Smith \ / ) P.O. Box 60941 = Boulder City, NV 89006-0941 _ / \ / \ _ TEL/FAX: 702-570-6108/570-6013 / /\ \ ] / /\ \ Mobile: 408-858-4528 | q-( ) | o | Email: d...@dsmith.org \ _ / ] \ _ / Website: http://www.dsmith.org --- - 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:
Re: [PSES] Single Point Grounding - Not Achievable at High Frequencies (greater than a few MHz)
Ahh... the common convolted and complex analysis discussing the issue with complicated explanationsand rationalizations. I may be way off in this, but it seems to work. So take a unit square of ground plane, or power plane, or reference plane, or whatever plane you'd like to call the intended return plane for any and all of the signals you are dealing with. You may have more than one plane and in parallel and common to the others. Note Mr. Woodgate's mention of proper layout. That is important! Now considering this unit square of plane, assuming one has not really mucked it up with splits and swiss cheesed with vias, etc. Can there be any lower impedance? What could be lower impedance than a plane? Does this plane not define the boundary conditions of so many simulations and models? It appears from physics (the one I was taught) that the unit square is the lowest impedance available. It is the definition of zero impedance since there can be none lower. Now we expand this plane to real world signal impedance and place a trace for a circuit over this zero impedance return plane. zero because there is none lower. (note, I am neglecting the multiple parallel paths as being an expansion of the simple case) We now have a loop based on the physical dimension of the trace over a plane. This, by Mawell? defines an inductance and thus an impedance. ps. End points are much more important than the very uniform (hopefully) trace between ends. Some real world caveats !! Skin Depth! Signal frequency determines skin depth and the amount of copper used for the plane becomes something to consider. Lower frequencies need a lot thicker copper to handle the skin depth such that signals on one side do not show up to any noticable degree on the other side of the plane. A really annoying crosstalk mechanism since it is not one that occurs very often so it is not high on the list of the usual suspects. Crude rule-of-thumb, single digit megahertz or less and half oz of Cu and you will likely have thru plane crosstalk in sensitive analog circuits. ps. my EMC world is about 50 kHz to 2.4GHz intentional, nevermind the unintended at 5-6 GHz. and about xmit 0 dBm to 15 kW all on the same brd and in plastic chassis. From: John Woodgate j...@jmwa.demon.co.uk To: EMC-PSTC@LISTSERV.IEEE.ORG Sent: Tuesday, May 21, 2013 3:35 AM Subject: Re: Single Point Grounding - Not Achievable at High Frequencies (greater than a few MHz) In message 1369105334.30674.yahoomail...@web160401.mail.bf1.yahoo.com, dated Mon, 20 May 2013, Bill Owsley wdows...@yahoo.com writes: Dr. Tom Van Doren demonstrates that single point grounding is not possible above the audio frequencies. Thus the lower cutoff in the regulations of 9 kHz. And that is really old school... The 'goodness' of single-point grounding is not a function of frequency alone. Circuit impedances are also involved, and this makes the issue so complex that no general rule is possible. Each single point has to be evaluated to determine the acceptability of the impedance between each point to be grounded and the single point and the impedances between the single point and every other single point in the assembly. The latter control the transfer of voltages or currents from one point to be grounded and others connected to the same single point, and between single points. The buzz-word is 'ground bounce' but it's not confined to digital circuits; ground bounce in analogue circuits is (normally) less abrupt but still present. -- OOO - Own Opinions Only. See www.jmwa.demon.co.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 - 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:
Re: [PSES] safety 60950 and surge suppression circuits
So the Safety engineer said the single fault condition was an open ground... Now what? A surge into a 300 volt SPD transfers that surge voltage to the open ground (chassis) and there is now a hazard !!! Thus the position, I've been told while sticking my fingers in my ears, The SPD's have to also meet the hi-pot test and not fire until the surge exceeds the hi-pot value. I argue that I cannot assure that the SPD's will operate, or the insulation will break down and conduct. In the same arguement is that MOV's cannot be used alone, but must be connected in series with a GDT that meets appendix Q?? And the MOV now has to be thermal fuse protected, and that is not current fuse protected. 60950 reference clauses mentioned elsewhere. I'm just the EMC engineer tryng to get surge to pass, while enjoying the little lightning balls that are launched with 4 kV surges. ps. put up a blast shield but the damn pieces bouncing off the walls and ceiling still got to me! From: Aldous, Scott scott.ald...@aei.com To: Joe Randolph j...@randolph-telecom.com; ri...@ieee.org ri...@ieee.org Cc: Bill Owsley wdows...@yahoo.com; EMC-PSTC@LISTSERV.IEEE.ORG EMC-PSTC@LISTSERV.IEEE.ORG Sent: Tuesday, May 21, 2013 6:25 PM Subject: RE: safety 60950 and surge suppression circuits Throwing in my 2 cents: Hipot test values are based on expected transients. The concern with the transient overvoltages is that they could punch through insulation needed for safety and subsequently hazardous voltages can be allowed to reach areas where they should not. The function of an SPD is to limit the level of transient overvoltages that propagate through the equipment. If the SPD functions correctly, the insulation should not be stressed by the transients since the SPD shunts the surge current to ground. In other words, the function of the SPD makes it different from the other insulation barriers. While the other barriers must withstand the transient overvoltages, the SPD functions to limit them. Because of the difference in function, it is appropriate to test them differently, or to treat them differently during test. As Rich stated, an SPD may not be reliable in its function to limit the transient overvoltages (for example SPDs are often themselves protected by fusing which then leaves the SPD function inoperable if the fuse opens), so it is appropriate to test the rest of the insulation as if the SPD were not present. Scott Aldous Compliance Manager/Engineering Lab Manager AE Solar Energy +1.970.492.2065 Direct +1.970.407.5872 Fax +1.541.312.3832 Main scott.ald...@aei.com 1625 Sharp Point Drive Fort Collins, CO 80525 www.advanced-energy.com/solarenergy From:emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf Of Joe Randolph Sent: Tuesday, May 21, 2013 3:41 PM To: ri...@ieee.org Cc: Bill Owsley; EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: safety 60950 and surge suppression circuits Hi Rich: The apparent contradiction that I was trying to describe can be summarized as follows: a) The safety insulation barrier must withstand a hipot test of, say, 1500 VRMS b) It is permissible to bridge this safety insulation barrier with a SPD that breaks down at, say, 300 VRMS In other words, in normal use, the safety insulation barrier can be bypassed by a SPD. For the seemingly artificial circumstances of the hipot test, the SPD can be removed in order to demonstrate compliance with the 1500 VRMS requirement. The 1500 VRMS safety isolation barrier would appear to be relatively useless if, in normal use, it is bridged by a 300 VRMS SPD. In the above example, I avoided specific reference to particular clauses in 60950-1, because I wanted to illustrate the basic scenario that seems to recur in a variety of places, but with differing details. In 60950-1, this scenario seems to appear in clauses 5.2.2, 6.1.2, and 6.2. It also appears in TIA-968 for equipment connected to the telecom network. Joe Randolph Telecom Design Consultant Randolph Telecom, Inc. 781-721-2848 (USA) j...@randolph-telecom.com http://www.randolph-telecom.com Hi Joe: Very quickly... SPDs are not considered reliable components or assemblies. The safety standards anticipate a failure -- anywhere from open-circuit to short-circuit. In the event of an open-circuit, there is no indication of such a failure. And, of course, all transients then pass through the open SPD. Consequently, the equipment safety insulations will be called upon to withstand the expected transient overvoltages. So, the standards require performing the voltage withstand test without the SPD in place. Best regards, Rich On 5/20/2013 1:40 PM, Joe Randolph wrote: Hi Rich: I'm hoping that you can provide one of your straightforward Rich Nute Explanations for the apparent contradiction behind the rationale that allows a surge protection component to be placed across a required safety isolation
Re: [PSES] Capacitor Discharge Test IEC 61010-1
A few decades ago when an intern, called co-op back then, a customer complaint came in that they had been shocked by the power plug after pulling it from the wall. No way said the engineers! Hey co-op go test this. We it turns out there can be the peak voltage left on the pins of the plug which will decay depending on the environment. And so the bleeder resistor. I thought the time frame was on the order of 250 mS. How fast can an operator get their fingers on the plug pins after pulling out? Sticking their fingers on a partial pulled plugged was dis-allowed. But those details were for the Safety engineers. From: Kunde, Brian brian_ku...@lecotc.com To: EMC-PSTC@LISTSERV.IEEE.ORG EMC-PSTC@LISTSERV.IEEE.ORG Sent: Tuesday, May 21, 2013 12:33 PM Subject: Capacitor Discharge Test IEC 61010-1 What we call the Capacitor Discharge Test in the IEC 61010-1 standard section 6.10.3 says that voltage across the pins of the power cord must not be Hazardous Live 5 seconds after disconnection from the supply. Most labs simply check to see if the voltage across the pins are 60 volts or less at 5 seconds, but the pass/fail criteria is the capacitive charge level described in 6.3.1 c) which is 45uC. 6.3.1 c) points you to Line A of Figure 3 but this chart seems to start at 100 volts. So how do I apply this chart if my 5 second voltage is 80 volts? Am I looking at this wrong or should this chart go down to at least 60 volts? Is there a formula that can be used instead of the chart? In our specific case, we are measuring the discharge of an RF line filter which has 4.4uF of capacitance across the line and the 5 second voltage is 80 volts. My guess would be this filter fails as-is without and additional bleeder resistor but when I discuss it with the company they pick apart the standard and the chart at figure 3. Another question. When you perform this test what line voltage do you use? The highest nominal voltage or do you include +10%? For 230VAC equipment do you test at 230Vrms or 264Vrms (373Vpk)? Thanks to all for any input. The Other Brian LECO Corporation Notice: This communication may contain confidential information intended for the named recipient(s) only. If you received this by mistake, please destroy it and notify us of the error. Thank you. - 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
