I have a test house giving me what I think are some funny numbers
on a dielectric withstand test for a switch mode power supply. It is a
component we buy off the shelf and use in our end equipment and I want to
balance what I know from the power supply vendor against what I’m getting
>from the compliance house, and what I see in the standard. I suspect the
compliance guy was wrong but I want to confirm and update my memory from long
ago.
It’s my memory that the component power supply would have two
dielectric withstand tests done during the type testing and that their test
values during type acceptance are higher than their, or the end user,
production line tests.
From table 5B I derive values of for basic insulation (Primary to
Chassis) 1500 Vrms and a re-enforced insulation primary to secondary 3000 Vrms
test value.
This is based on a working voltage of less than 350 V peak in the
switcher, a number I’m only assuming to be correct but its certainly within
the range I remember from 10 years ago. The values should correspond to table
5B in UL 60950-1
The end use product would simply be a 1500 Vrms test for a minute
between line and equipment chassis. The test time can be less but I can’t
remember the voltage value if the test time is decreases.
The actual problem I’m having is that the line to ground
capacitors on the pcb are blowing up at the figures the test house gave me and
which are significantly higher than what I indicate above. Unfortunately they
also arc during the surge testing at 2Kv and die there as well. I want to make
certain my understanding is correct before I begin working with the power
supply manufacturer and I think that I really only have a surge test problem
and not an insulation problem.
If you power supply guys could put me on the straight and narrow
path based on you knowledge I would appreciate it.
Gary
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