Isolation derating of flyback transformer

Thread Starter

DivadLarsen

Joined Mar 7, 2010
2
Hello,
I'm designing a small flyback transformer (~30W), single output. The issue of my design is the input common mode voltage, that's specified as "up to 1500V indefinitely".
Now, I can easily get 1500V rated transformers, but the rating is usually 1500V for 1 second or 1 minute.
Alternatively I can get 4kV isolation for 1 second/minute, but this may be overkill.

What I am curious about is how I calculate/derate to the max. isolation voltage for indefinite usage (or just 1 day, if easier).

I've been referred to the IEC 61558-2 standard, but like everybody else I don't want to buy it, if it doesn't answer my question (standards rarely do) :)

Does anyone have experience with this type of issue?

Regards!
 

Ian0

Joined Aug 7, 2020
2,226
Your local public library will have a copy of the standard.

Note: check whether the voltages are peak or rms. It makes 41% difference!

Does your transformer really need to withstand 1500V indefinitely? Where is it being used?
 

Thread Starter

DivadLarsen

Joined Mar 7, 2010
2
Your local public library will have a copy of the standard.

Note: check whether the voltages are peak or rms. It makes 41% difference!

Does your transformer really need to withstand 1500V indefinitely? Where is it being used?
Hi Ian,

thanks for your reply; I will definitely check out the library! I haven't had much luck in finding Standards there in the past, but it absolutely worth a shot!

The PSU is placed differentially somewhere on a string of solar panels, with a potential accumulated DC voltage of 1500V - hence the requirement.
I do realize the actual requirement may "only" be up to 14 hours per day - but that seems very close to indefinite in my experience :)

Regards!
 
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