Posted on behalf of a colleague:
The Electric Strength test conducted after abnormal testing in accordance with
IEC 60950 may be performed at room temperature, after the EUT has cooled down.
5.3.8.2 says the test is to be conducted in accordance with 5.2.2. 5.2.2 does
not say anything about temperature, so the default is to allow testing at room
ambient.
For those cases in which the electric strength test is to be conducted in a
well-heated condition, 5.2.1 is referenced, which indeed states this. The
choice of reference to 5.2.1 or 5.2.2 was the subject of much debate in TC74.
I can assure they were not arbitrary.
The logic? Failure of insulation after an abnormal test is more akin to
failure of insulation on the production line. That is, some influence (energy
force) caused catastrophic failure of insulation. Temperature is likely to play
only a small role in determining the long term integrity of the insulation
under these circumstances.
>From a practical point of view, it would be very time consuming and costly to
always perform the Electric Strength test immediately upon termination of a
simulated fault test, especially when the test is terminated by the opening of
a component. To test while still in a heated condition would require constant
monitoring of testing during working hours and would not allow testing to be
conducted unattended.
As a result, TC74 felt the value of conducting the Electric Strength test with
the equipment in a well-heated condition after a fault test does not justify
the cost.
Regards,
The Unknown Standards Guy
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