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Inductor for high voltage buck converter has enough insulation on windings?

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treez

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Hello,

We have a ~330V to 14V at 140mA Buck converter based on LNK302D. We are suing a 2.2mH inductor for the buck. This inductor is wuerth 7687714222.

Wurth 2.2mH inductor…7687714222
https://katalog.we-online.com/pbs/datasheet/7687714222.pdf

Do you think the insulation on the windings of this inductor is suitable to stand off the ~330V that will exist across this inductor during the FET on times?
 

I would suggest high voltage tested 768775322 instead. Or ask Wuerth.
 
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Thanks, but our original inductor, of post one above, is tested to 400v surge. And if anything, surely our inductor would be better than the 768775322, because it is bigger and so the windings possibly less “squeezed together”
I am wondering if we are failing EMC because this inductor is breaking over and large spikes of current are going through it.

768775322 INDUCTOR 2.2mH
https://www.mouser.com/ds/2/445/768775322-539416.pdf
 
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The dielectric strength specifications of both parts are tiny. A 400 V DC surge specification doesn't tell much about permissible working voltage.

I understand the "high voltage" qualification of two inductor series so that they are 100 % production tested, that's apparently not the case with standard series.
 
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Thanks, but i am not sure where you found the data for the dielectric strength?

Was it here..where it says its designed for 400VDC applications?...the 768775322 inductor...
https://katalog.we-online.de/en/pbs/WE-PD-HV?sid=e21aa54d6c

..ok so ive just read on this page that the WE-PD series is actually designed for use with our controller, the LNK302, so therefore it must be rated for the high voltage.
 

I didn't read the first datasheet thoroughly. I thought it's standard PD series, but it's in fact HV PD series, similar to HV PD2 series I mentioned in post #2.

Sorry for the confusion. Both should by equally well suited for your application.
 
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This is a related problem to the above...

Hello,
We have an offline , non-isolated buck converter providing 14V at 0.14A output. We have a PI filter (attached) at the input to help EMC. The inductor of this PI filter is a 470uH inductor (Wuerth 744045471)

744045471 inductor (470uH)
https://katalog.we-online.com/pbs/datasheet/744045471.pdf

We are worried that we are damaging the insulation on the windings of this inductor due to the high voltage ringing that occurs across this inductor whenever the mains is applied at mains peak (ie when the power supply is turned on at the instant of mains peak voltage). The ringing voltage which occurs across this inductor in these situations is as attached. –It rings up to 350V.
Do you think we are damaging this inductor like this?
 

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  • PI filter.jpg
    PI filter.jpg
    19 KB · Views: 136
  • Ringing Voltage across 470uH inductor.jpg
    Ringing Voltage across 470uH inductor.jpg
    38.9 KB · Views: 127

I would expect an enameled copper wire insulation breakdown voltage > 500V. In so far it's unlikely that the inductors are damaged by occasional 350 V surge events. But the parts are not specified or even tested for this pulse voltage.
 

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