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Re: DIY HV transformer

Original poster: Steve Conner <steve@xxxxxxxxxxxx>

> Do you, or anybody of this list, know the procedure
> how to calculate this?

All I know is, the area and length of the shunt have
very little to do with it. Shunts always have air gaps
for the same reason that ballast chokes do, and it's
mainly the air gap that determines the leakage
inductance (or coupling if you prefer). The leakage
inductance should be about the same as for an
iron-cored choke with the same airgap geometry (ie
width and area) as your shunt.

The shunt just needs enough cross sectional area to
stop it saturating, because if it does the transformer
might as well be completely un-shunted. If you make it
the same CSA as the transformer core, then it will not
saturate even if the secondary is completely shorted
and the shunt has to take all the flux. MOTs probably
get away with undersized shunt iron because they never
have to drive a short circuit.

If you're shunting an E-I core transformer then you
use two shunts each with equal airgaps and half the
CSA. For calculations, they count as one shunt with
the same gap width and the CSAs added together.

Sorry I don't have any hard data, but if I were trying
to make a current limited transformer (or ballast
choke- it's the same thing) I would just use trial and
error to determine the shunt air gap.

Steve Conner