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Registered Member #2655
Joined: Wed Jan 27 2010, 04:09PM
Location: Czech Republic
Posts: 18
Hi, I'm a little bit curious - I was doing a little research on the (DR)SSTC field and I've figured out that most of you are driving gates of your IGBTs at 24V or even 30V. But on the other side, there's usually listed +-20V as an "Absolute maximum rating" for the Vge. So, is there any way, how can I safely measure how far can I go (cause I don't like to risk blowing gates)?
Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
Yes, crank up the gate voltage until the IGBT is destroyed, then back it off a little.
A more sensible approach is to decide how much primary current you want, and look at the IGBT datasheet to see how much gate voltage corresponds to that current. You may not even need to overvolt the gate, or you may decide to upgrade to larger IGBTs that can handle more current without needing overdriven. My Mjollnir DRSSTC runs at 15V gate drive and about 450A primary current.
However, most DRSSTC builders don't work this way, their answer to the design question "How much primary current" is just "Moar!"
Registered Member #2655
Joined: Wed Jan 27 2010, 04:09PM
Location: Czech Republic
Posts: 18
Steve McConner wrote ...
However, most DRSSTC builders don't work this way, their answer to the design question "How much primary current" is just "Moar!"
Well, I can't go this way - at least not now because I'm limited by the circuit breaker - average current 16A at 230V. Well, with interupter duty cycle<5%, I can still get quite huge primary current :)
Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
Mrkva wrote ...
Well, with interupter duty cycle<5%, I can still get quite huge primary current :)
Yes, that is the whole point of a DRSSTC. A typical interrupter duty cycle would be something like 1% to 2%. (roughly 100us burst length, 100Hz repetition rate)
A good medium-sized DRSSTC will have maybe 50 to 100kW output power during the burst. You can't run that off a wall outlet with more than a few percent duty.
Registered Member #15
Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068
Earlier on during the DRSSTC boom in the first part of this century, there was a trend for over-voltaging the gates. However, in my experience, i really haven't found much benefit to it, even though i sometimes myself still do this. But for most designs, i usually run about 15V maximum (1:1 GDT) on the gates.
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Gate-emitter voltage question
