Thanks for the information. But in this case breakdown is occurring and the question is if it can be problematic.
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 5:02:05 PM To: EMC-PSTC@LISTSERV.IEEE.ORG <EMC-PSTC@LISTSERV.IEEE.ORG> Subject: Re: [PSES] major safety issue possibly affecting 20% of the electronic devices in use Hi John and Doug: Some years ago, HP-Agilent-Keysight-Avago did a study of endurance of opto-isolator isolation. The results were published in Application Note 1074. Clearly, opto-isolator solid insulation withstands many hours at 1.2/50 us test voltages. I assume that ordinary solid insulations behave similarly. Enjoy! And best regards, Rich From: John Woodgate <j...@woodjohn.uk> Sent: Thursday, February 27, 2025 2:42 PM To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: [PSES] major safety issue possibly affecting 20% of the electronic devices in use Have I understood correctly, that after 100 000 of the 800 V pulse test, the EUTs failed the normal hi-pot test? This is not a test on newly-made products, to which IEC safety standards are applicable. Of course, the tests in such standards can be applied to products that have seen service, but failures are to be expected. On 2025-02-27 21:32, doug emcesd.com wrote: 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. 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