Hi Rich and the group,
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: Wednesday, February 26, 2025 16:16
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
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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
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