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I was using bars across the IGBTs. The batteries where connected through a contactor to the busbar. The capacitors, though, were connected to the bus bar with 2 or 4 gauge wire. It was way too long too. What a recipe for disaster! I've since bought a 66uF 800V film cap that can handle 100Arms. It is now bolted directly to the bus bars. My calculations suggest that this should result in a total of about 15V ripple at 100Arms AC ripple current. However, I also got some 1500uF 450V elcos. I might try to get bars long enough to put one or two of those on the bar too. That will make the bar sort of long though. I suppose the real question now is, what sort of ripple might the busbars experience? If I run a motor up to 250Arms then what equations should I use for the AC ripple at the caps? From what I can gather it seems that the AC ripple of a three phase system should be approximately half of the Arms to the motor. This would give me about 125Arms at the caps at peak output. Additionally, I might want to clamp the ripple voltage to less than 15v so I'll need more caps because of that too. So, I think I'll need a bit more than just my 66uf film cap but maybe not until I start really loading the motor. I'm reading that elcos in the system were mostly used in VFDs because they input rectified mains voltage and thus have very ripply voltage input. A battery is very stiff and constant so it seems like tons of capacitance is no longer needed. Instead, the caps in that case are just to deal with the ripple current and to decouple the IGBTs from the batteries.
I have a ton of PDFs about this whole situation but I certainly wouldn't reject suggestions either directly or for other PDFs or books I might want to read.
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