Hi Rich, If there is a true air gap not involving other material then I agree with you. Then the only problem is with medical as those cross gap discharges are essentially ESD events and will cause response from tissues.
If the “air” gap is on a circuit board then we have a problem. If I breakdown a gap on a board with a million discharges (a number easy to reach in a month in the field with EFT plus the following multiple discharges that follows each pulse) I think there is danger of forming a conductive path on the board, decades ago we called these “carbon tracks.” I have observed these since I started designing and building high voltage circuits in 1963 (it’s a wonder that I did not electrocute myself back then). The little supply that generated some of the data for the paper used to have this effect only below 3,000 Volt pulses with the "sweet" spot at 800 Volts. But now it will exhibit this behavior above 3,000 Volts as well so something has changed in the supply. I have confirmed this effect at three locations using different ESD guns, different scopes, and different power supplies. Doug Smith Sent from my iPhone IPhone: 408-858-4528 Office: 702-570-6108 Email: d...@dsmith.org Website: http://dsmith.org ________________________________ From: Richard Nute <ri...@ieee.org> Sent: Thursday, February 27, 2025 11:27:30 AM To: doug emcesd.com <d...@emcesd.com> Cc: 'Pete Perkins' <peperkin...@cs.com>; EMC-PSTC@LISTSERV.IEEE.ORG <EMC-PSTC@LISTSERV.IEEE.ORG> Subject: RE: major safety issue possibly affecting 20% of the electronic devices in use Hi Doug: Thanks for your response and especially your paper. Thanks to Figure 1, I am no longer alarmed by a possible breakdown of insulation between primary and secondary. In Figure 1, I see the set-up: NkdkJdXPPEBannerStart Be Careful With This Message >From ("Richard Nute" ><ri...@ieee.org>)<https://godaddy.cloud-protect.net/email-details/?k=k1&payload=53616c7465645f5f7a8501fdebf05b82472467f6ee236ff2525271ff2883c89137283345899be5ac2fe4423e728d1032fd43b4004cee5a96bd6cc9707032d1eae62815c69888def3dbbfe2fe1e10e2e4a1fc3a13d810094fbcea80f43d27d54edb4ba3937f754bfca38100240473576de1d8f603e9943c360560529733582bd222c873cf34f3991ee3707f260f4f1bd0258d6b26aa12a17b3771a12f6f59cee2c9c98cc2481e035072b11fb52448543b2e093036c1499e271f7812b96a3e6267fc7988551fe77562ff9fff2fb94550a26d905987762d28975d073431802603a1> Learn More<https://godaddy.cloud-protect.net/email-details/?k=k1&payload=53616c7465645f5f7a8501fdebf05b82472467f6ee236ff2525271ff2883c89137283345899be5ac2fe4423e728d1032fd43b4004cee5a96bd6cc9707032d1eae62815c69888def3dbbfe2fe1e10e2e4a1fc3a13d810094fbcea80f43d27d54edb4ba3937f754bfca38100240473576de1d8f603e9943c360560529733582bd222c873cf34f3991ee3707f260f4f1bd0258d6b26aa12a17b3771a12f6f59cee2c9c98cc2481e035072b11fb52448543b2e093036c1499e271f7812b96a3e6267fc7988551fe77562ff9fff2fb94550a26d905987762d28975d073431802603a1> Potential Impersonation The sender's identity could not be verified and someone may be impersonating the sender. Take caution when interacting with this message. NkdkJdXPPEBannerEnd Hi Doug: Thanks for your response and especially your paper. Thanks to Figure 1, I am no longer alarmed by a possible breakdown of insulation between primary and secondary. In Figure 1, I see the set-up: Pulse generator -> cable -> probe -> cable -> power supply -> ground Within the power supply: Secondary circuits -> solid insulation, air insulation, EMI capacitance, transformer winding inductance -> primary circuit >From a safety point of view, I see a complex capacitance coupling current (and >possible inductive effects of the transformer windings) to the primary >circuit. But, I don’t perceive any dielectric damage. Thanks again, Rich Ps: I would expect a difference in the current waveforms between Figures 1 and 2 configurations. From: doug emcesd.com <d...@emcesd.com> Sent: Wednesday, February 26, 2025 8:27 PM To: ri...@ieee.org Cc: 'Pete Perkins' <peperkin...@cs.com>; EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: major safety issue possibly affecting 20% of the electronic devices in use Hi Rich and the group, Accidentally hit send on the last one. Here is a link to the paper: https://emcesd.com/pdf/An_Unusual_Source_of_Multiple_ESD_Events_in_Electronic_Equipment_final.pdf<https://urldefense.proofpoint.com/v2/url?u=https-3A__emcesd.com_pdf_An-5FUnusual-5FSource-5Fof-5FMultiple-5FESD-5FEvents-5Fin-5FElectronic-5FEquipment-5Ffinal.pdf&d=DwMFAg&c=euGZstcaTDllvimEN8b7jXrwqOf-v5A_CdpgnVfiiMM&r=c9NR2mGfldry-2pM9Bbuww&m=tP4ynwqzldJBFpq8iMilqEevrzZeqxneKUW-xaGcWoqbmd9pw8D2X6uhVIqHLn3Y&s=RaBr8PHRC7w6R7th2YG58KCbStWnsaXTOYaftCWCVLo&e=> I think resonance in the EMI filter with a Q of 5 could do it. I was in the lab today and determined the effect is due to the long tail on ESD and EFT events, not the fast rise time. I got some very good scope shots of the phenomenon today. In the past I have observed the effect in both small two wire supplies and even in a 1.5 kW supple in a semiconductor fab. I did not realize the safety implications when I wrote that paper. Later on and I started to think how that phenomenon could happen is when the light bulb went off in my brain. I plan to build a suitable pulser with no moving parts to wear out to see if I can induce damage. I can build such a pulser in about an hour with parts I have laying around. It will produce pulses with a few ns rise time and a 300-500 ns fall time with an amplitude of 1200 Volts or so, a very easy thing for me to assemble. An ESD gun will work but with a lot wear on the HV relay to make 100,000 pulses. Doug Smith Sent from my iPhone IPhone: 408-858-4528 Office: 702-570-6108 Email: d...@dsmith.org<mailto:d...@dsmith.org> Website: http://dsmith.org<https://urldefense.proofpoint.com/v2/url?u=http-3A__dsmith.org&d=DwMFAg&c=euGZstcaTDllvimEN8b7jXrwqOf-v5A_CdpgnVfiiMM&r=c9NR2mGfldry-2pM9Bbuww&m=tP4ynwqzldJBFpq8iMilqEevrzZeqxneKUW-xaGcWoqbmd9pw8D2X6uhVIqHLn3Y&s=1i3LVauSapb-sFcpt0k7VIs85Bqx1xUSa1qeYh-4fXE&e=> ________________________________ - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. 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