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Registered Member #3900
Joined: Thu May 19 2011, 08:28PM
Location:
Posts: 600
Just a few more questions about my drsstc... Mostly involving ct's and gdt's. First off, can I use a brass bolt through my ct's(overkill, I know)? Last time I checked brass wasn't a very good paramagnetic material. Will it work? And two: in Steve's coil(don't ask me which one) he uses two 1:2:2 gdt's with primarys in parallel. How does this work well? Ferrite isn't very precise, so with a total of +-20% difference between the cores, won't one drop more voltage over its primary than the other?
Registered Member #2292
Joined: Fri Aug 14 2009, 05:33PM
Location: The Wild West AKA Arizona
Posts: 795
On the first question yes you can use brass it will work just fine.
Second question, the difference between core permeability even in the +-20% range will not be a big deal. I frequantly use 2 or even 4 GDTs with paralleled primaries. Even if the voltage difference between two GDT was as bas as +-2 or 3 volts (which it wouldn't be) it still wouldn't be bad because there are is a large range in which the gate will be fully saturated on the IGBT. This range is usually between 10v and 24v.
Registered Member #195
Joined: Fri Feb 17 2006, 08:27PM
Location: Berkeley, ca.
Posts: 1111
Qestion 2: a trick that I lerned from Steve Ward is to wrap cat5 around a toride and then use 4 of each twisted pair and combine them in prallel for the primary. the second of easch pair drives each gate. since there is 4 pair this works out great
Registered Member #3900
Joined: Thu May 19 2011, 08:28PM
Location:
Posts: 600
Yea, I do a similar thing. I take cat5, then I remove one twisted pair. Then I put green stripe and green solid I series, blue stripe and blue solid in series, orange striped and orange solid in parallel. Removing the outer sheath gives less leakage inductance, plus you don't even need the fourth pair as you are making a 1:2:2 transformer. Because I am driving the primary with +-15v, I need a 1:2 ratio. If I had Steve's MOSFET gate driver I could get away with 1:1.
Registered Member #3900
Joined: Thu May 19 2011, 08:28PM
Location:
Posts: 600
Hmm... Interesting. I may have to give those a try. I posted a while ago about a driver using these, but some people told me to use the ucc's instead. 14 amps is pretty nice though. Plus beats heat sinking that alows for harder driving, I may have to give these a second go.
Registered Member #3900
Joined: Thu May 19 2011, 08:28PM
Location:
Posts: 600
actually, if anyone is still following this thread, any ideas on what my ~fres should be? i was first shooting for 200kHz, but realized i had to change it for other reasons anyways. i am using hgtg30n60b3d igbt's. t think this was a little to high anyways. 180k? 150? i am trying to keep this a small coil, so nothing that requires more than 18" tall secondary.
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Moar drsstc help!?
