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Old 07-08-2016, 09:44 PM   #2791 (permalink)
MPaulHolmes
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One possible guess is with the 165degree out of phase, it could get a DC bias going in the line filter, and maybe the line filter saturates, which would drastically reduce the inductance and makes the current coming from the driver too high. I moved to the ixdn604si that is surface mount, and has a metal tab on the underside for removing heat. I was noticing that the "no heat tab" version would get hot the touch (but not freakishly hot), but still worked. Hearing your results makes me think that there is too little headroom for that driver chip. But with the metal tab, they stay cool even switching 1200v 600amp IGBTs (I tested it over the last couple weeks on a grid tie). I'll be doing new driver boards that are all on the top side. They also use cheaper 10uF 1206 caps rather than the big fat 1210 caps.

Another issue I discovered about a week ago is, the FOD8316 pin 8 is sometimes NOT connected internally to ground, even though the datasheet says it is. So, I had to add a connection to ground from pin 8 (it allows turning on the LED inside) on the 3 phase grid tie board I recently did. I'm going to get new driver boards made. I'm very sorry it's causing you so much trouble.

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