Quote:
Originally Posted by esonson
If this becomes a nice 'black box' module system with software configurable low power module and plug-in high power module, then this could meet controller requirements from scooter to dragster.
Anyway, since I was thinking 156+volts and pushing 600+ amps, what changes would be necessary in order to guard against pushing the envelope like I am thinking of doing and not creating that dreaded magic smoke?
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Going much over 156v is probably not a safe thing for the 200v mosfets. In fact, 144v is probably the safe peak. I looked it up, and there ARE higher voltage mosfets that are reasonably priced. However, their heat loss is about 3 times that of a really good 200v mosfet. They are only about $7 each.
250v mosfets
Hmm... You'd need higher voltage diodes, which I don't think is any problem, and then you'd be just fine for 192v. I don't know the safe paralleling limit on the mosfets. I'm doing 10 for this first attempt. Ian is using 12 to get 600 amps. I bet you could do 18 if you used 2 or 3 different mosfet drivers. I don't see why it wouldn't work. The control board would be the same up to 900 amps. After that, you would need a different current sensor. I don't know if any exist above 900 amps. I haven't seen any on digikey or mouser.
The nice thing about this design is that if you change the mosfets/diodes, everything else doesn't care about the higher voltage. If you throw in some 300v mosfets, the controller will run on anything from 12v to 300v. The key is that I'm using an isolated DC-DC that powers the controller with the 12v car battery. Most controllers use DC-DC's that have limited inputs like 90v-156v or whatever. That's why most controllers have strange voltage input ranges.
Another option is IGBTs. Ebay often has some 1200v 600amp IGBTs for pretty cheap. I once bought 4 for $50. They have a fixed voltage drop, so are less efficient at lower voltages, but if you do a good liquid cooling cold plate, I think it would work really well. Then, you could have any voltage you want, and very high max current. That's what the Tesla's CTO did before working at Tesla. It's actually pretty simple (ish).
Actually, for higher current sensing, you could use 2 current sensors in parallel. You could have 2 separate M-'s! That's be sort of weird, but at least you could monitor currents up to 1800 amps.