Capacitor Bank for Open Revolt: What Size?

[adamj12b]

Originally Posted by Nevyn

So I'm working on our controller using the new and improved controller PCB, the SMD current sensor, and the VLA based IGBT driver from mrbigh.

Here's what we got for IGBTs: 4x Fuji 300A 1200V

Running these IGBT's together would give 1200A. We plan on setting it to 1000A max current.

Based on what Paul said long ago in the main thread:



5% of 1000 is 50A; I'd rather have a little more room for error, so let's say 8% (80A).

Is capacitance tertiary to getting a low ESR and high ripple current rating, or does it matter just as much?

Looking for best as well as least expensive route.

Thank you all!

Sorry im late to the party.

The quote from Paul was interpreted wrong.

"You only need like around 5% of the max current for ripple rating, so they say. 50% is the worst case scenario."

Its 5% of the max current of the worst ripple. The worst ripple is at 50% duty so 500A then take 5% of that. I like to work higher then that in the 25% area, 125A.

Like DJ said, your best bet is to use a bunch of low ESR caps in parallel and throw in some polyester or polypropylene caps for high current rating. But be careful for ringing.

What voltage do you plan on running with these IGBT's?

-Adam

[Nevyn]

Not more than 144VDC. Well withing derated margin, yes? 4x300=1200A, set controller to 1000max limit, not that we'll ever see 1k amps without serious money into batteries.

I like JackBauer's approach of "Few big, few small." However, I'm not sure if it will cost more or less to go that route as opposed to "hordes of small."

[FieroChris]

I have been digging for several hours now.... looking for a schematic of where these big caps go....
I love adams and (something alaska) have been doing with the ring cap and the IGBT's



it looks soooo sweet...

question is:

do the caps go on the supply side of the motor controller?? this is the only reason a B+ goes to the motor controller ?? since the controller turns on and off the M- ??

does the third lug of the IGBT go to anything ??

how does the IGBT get wired up ??

B = battery -
C = motor - ??
A ????

[adamj12b]

Originally Posted by FieroChris

I have been digging for several hours now.... looking for a schematic of where these big caps go....
I love adams and (something alaska) have been doing with the ring cap and the IGBT's



it looks soooo sweet...

question is:

do the caps go on the supply side of the motor controller?? this is the only reason a B+ goes to the motor controller ?? since the controller turns on and off the M- ??

does the third lug of the IGBT go to anything ??

how does the IGBT get wired up ??

B = battery -
C = motor - ??
A ????

I covered some of this in my Uprising thread, but i will do so here as well for informational purposes.

The cap goes on the supply side as close as possible.

The terminals on the IGBT are

A = Motor Negative (M-)
B = Battery Negative (B-)
C = Battery Positive / Motor Positive (B+/M+)

The most important factor of a motor controller capacitors is not the capacitance, but the ripple current ability. You must be able to control and withstand the current pulses or else you will destroy things.

-Adam