Flyback transformer isolation requirements

[themaccabee]

Hi,

I need to investigate if a flyback transformer is suitable for an application.

Product requires to pass EN 60255-5 dieletric tests of 2kV /50Hz and impulse tests of ±5kV 5 positives & 5 negatives 1,2/50µs.

So does this mean the transformer selected must have an isolation of atleast 5kVDC , or does a transformer with lower stated isolation (like 2kVrms) will withstand higher impulse test (>2kVrms) since it is a pulse wave form unlike 50Hz continuous sine wave used in dielectric test?

Experts plz convey your opinion..

Thanks,

 

[chuckey]

As you approach the voltage limits of an insulator, stressing it with voltage degrades it, hence the specified number of pulses. Its a commercial judgement, design it down for the test or design it up for a long life with minimal complaints. I would be unhappy to think that my airliners electronics were built to JUST pass the test.
Frank

 

[themaccabee]

Thank you chuckey,

I would like to make the question little more clear..
Its basically the difference between Dielectric Test & Impulse Test impact on material.

Impulse test means short duration ( in my understanding ) so whether a dielectric would withstand higher voltage levels for that if material is specified for some isolation voltage..

for eg.. if we select a mosfet the continuous drain current may be 5A but peak pulse current rating may be 80A
I want to know if a similar concept is applicable here??