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Re: Skip's DRSSTC
- To: tesla@xxxxxxxxxx
- Subject: Re: Skip's DRSSTC
- From: "Tesla list" <tesla@xxxxxxxxxx>
- Date: Wed, 28 Sep 2005 16:34:15 -0600
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- Resent-date: Wed, 28 Sep 2005 16:36:14 -0600 (MDT)
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Original poster: Steve Ward <steve.ward@xxxxxxxxx>
Hi Skip
Question: These IGBTs do not have internal diodes. Presently I have
400v bidirectional surge suppressors external to the IGBTs. Is this
considered sufficient?
NO WAY! You *must* have a diode across each IGBT. Its some sort of
miracle that they havent failed yet. I do note that you are running
7AAC input for only 18" sparks... how hot are those IGBTs getting??
I am going to raise the AC input voltage up to 240, a little at a
time. Can I increase the suppressor voltage to, say, 500v ?
You should use around 440V for the clamping (2x 220V TVS is what i
use on my coils). This allows for 420VDC max which is usually plenty
for some big sparks.
If you are using these IGBTs in an H-bridge at present and are using
them on DC, can you let me know the maximum DC that you have used
successfully?
They should be fine to 400V... assuming you 1)put those diodes in
there! and 2) have sufficient decoupling capacitors and TVS on each
IGBT, also be sure to minimize (and i really mean *minimum*) the
inductance between IGBTs, and their TVS and decoupling caps.
Steve
Skip