Dear Boštjan:
So in reality no way to avoid abnormal testing,
since on transformer we always measure >42,4Vpk.
Chances are, when you fault (short) primary to
secondary, the switcher will shut down, and the
output will not exceed SELV (will likely be zero).
If this is the case, then no requirements for
safety insulation between primary and secondary.
The test proves that in the event of failure of
the insulation primary-to-secondary there is no
"hazardous" voltage. So, the insulation is not a
safeguard and need not meet the requirements.
On the other hand, no testing is necessary if the
separation between the hazardous voltage and the
secondary meets the requirements in the standard.
Good luck, and best regards,
Rich
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