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Old 03-21-2011, 07:56 AM   #4509 (permalink)
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Originally Posted by MPaulHolmes View Post
I think IGBTs, like diodes, have the property that the hotter a device gets, the lower the voltage drop. So, if you have 2 in parallel, the hotter one hogs more and more of the current, and can lead to thermal runaway. If you can keep both reasonably close in temperature, it's not so bad to run them in parallel.

Yeah i just caught that in that paper that i linked in my last post. it stated that keeping the igbt's thermally "tightly linked" was very important in ensuring that they shared the load somewhat equally (within about 20 percent of each other.) Higher total current actually led to better load sharing, as did higher temperature (as they heat up they share the load more qually,) higher switching frequency and lower duty cycle.

At least according to what i read in that paper, it looks like 3 of the devices could reliably be run in parallel, as long as they could be well thermally linked (share the same heat sink.)

would anyone on here happen to know of a better place to buy new igbt's than ebay? DJ made a good point that pre-used ones probably aren't going to be very well matched.
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