DC bus calculations

[Gaber Mohamed Boraey]

Hello

This is 12kw UPS board, 3 phase, as you see there is 5 capacitors in parallel and each two are series together

I've checked the board for blown igbt and doide, and found the igbt is 75n65fl2, 75 ampere and 650v, we have the igbt, but not the doide and we're looking for replacement one
The doide is MM60fu120B, which is 60 ampere and 1200v, my question is that can I use lower voltage doide?, for example 600v?,
The capacitors are 450v rated which means that voltage at the capacitors can not exceed the 450v, if 2 series capacitors, the voltage can be higher at the negative and positive terminals of DC bus at those capacitors?, if so how much can be?, as estimation?
The batteries are 20 battery 12v which is 240v DC on series
Can we calculate the DC bus voltage so we estimate the voltage on the inverter circuit?, or estimate the voltage at the igbt and doide? according to the capacitors configuration?
Assuming the inverter is T-shape inverter and circuit similar to this

 

[danadakk]

The C's in series, if equalizing R's used across them, would be good for
900V. RMS values, not peak, not transient, which usually cause failures
if underrated. Check C datasheet if you can to see if its rating is RMS or
peak.

Personally not knowing the board designer or his reasons for choices, and
I am guessing the value of the board, I would replace with same ratings as before.

 

[Gaber Mohamed Boraey]

The C's in series, if equalizing R's used across them, would be good for
900V. RMS values, not peak, not transient, which usually cause failures
if underrated. Check C datasheet if you can to see if its rating is RMS or
peak.

Personally not knowing the board designer or his reasons for choices, and
I am guessing the value of the board, I would replace with same ratings as before.

Yeah, I'm trying change same rated values, but just the doide hardly find, that's why I'm asking here trying to get close to the DC bus value
I was thinking of similar machine and measuring the DC bus and then I know the voltage rating at this place