OLTC Questions

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Original poster: "Stephen Conner by way of Terry Fritz <teslalist-at-qwest-dot-net>" <steve-at-scopeboy-dot-com>

Hi

This post is aimed at Terry Fritz and others working on the new OLTC 
technology. I read about this just today and I was pretty impressed. I 
would very much like to try messing around with this in a small 100-200 
watt size but there are a couple of things I'm not sure about:

1. How do you make sure your IGBT switch turns off at a primary current 
zero? I imagine that if you turned it off when the primary current was 
high, it would blow up. Do you have some kind of current sense circuit or 
are you just waiting until the ringdown is definitely over?

2. Would a SCR or triac work instead of an IGBT? I don't know if SCRs can 
be made to turn on quickly enough, but they would sure simplify things 
because they automatically turn off at a current zero :)

Any thoughts on the matter much appreciated

Steve C.