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 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: [email protected] Website: http://dsmith.org ________________________________ From: Richard Nute <[email protected]> Sent: Wednesday, February 26, 2025 4:16:45 PM To: doug emcesd.com <[email protected]> Cc: 'Pete Perkins' <[email protected]>; [email protected] <[email protected]> Subject: re: major safety issue possibly affecting 20% of the electronic devices in use Hi Doug: I am alarmed that you experienced breakdowns by an 800-volt pulse when the dielectric strength of the primary circuits is at least 1500 volts rms. I have a few questions: 1. 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Take caution when interacting with this message. NkdkJdXPPEBannerEnd Hi Doug: I am alarmed that you experienced breakdowns by an 800-volt pulse when the dielectric strength of the primary circuits is at least 1500 volts rms. I have a few questions: 1. What was the 800-volt waveform? You applied the pulse common mode, which I assume is to both line and neutral conductors connected together and to the ground wire. (This is the hi-pot test configuration.) Please confirm. 2. How did you detect breakdowns, especially in the next microseconds after applying the pulse? 3. Small wall-warts are typically two-wire with no ground. (The hi-pot test is to foil wrapped around the enclosure and to the secondary.) What was your test configuration? 4. Primary-to-ground and primary-to-secondary in a typical product consists of Y capacitors, solid insulation, and air insulation. Since the air insulation is 2 mm or more, this is unlikely the site of the breakdown. Solid insulation should easily withstand 800 volts (more likely 8,000 volts). So, this leaves the Y capacitors as likely suspects. What is your guess as to the EUT component that exhibits this phenomenon? 5. Were any of the units you tested malfunctional or permanently damaged due to your tests? 6. How can we get a copy of your paper? Thanks, Rich - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. 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