Comms isolating transformer breaking down during hipot test

cupoftea

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Hi,
We have an OffTheShelf signal isolating transformer in a comms setup.
The transformer and the comms driver is on the secondary side of an offline SMPS.
So we need to do a hipot test from SMPS_primary to the output of the signal transformer.
However, this always causes break down, (of the signal transformer) since the pri:sec capacitance of the signal
transformer is less than the pri:sec capacitance of the SMPS isolation transformer...so therefore most of the hipot voltage goes across pri:sec of the isolating signal
transformer.
How do you get round this?
 

The test is apparently exceeding signal transformer breakdown voltage. What's the use case? Either transformer rating is insufficient or test setup inappropriate.
 

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