Protecting Inverter from inductive spike during fault scenario

[ImportFanatiK]

I watched Damien's video and have been reading about all of the failed inverters due to loosing power from contactors turning off while in motion, and am trying to confirm the best setup to prevent this from happening to me.

Below is what I am thinking, could anyone confirm if this sounds right or if there is anything else I can do?

1. Ensure the OpenInverter board is in control of the contactors, not BMS or something else.
   (If the BMS needs to controll them it can send CAN commands to the OpenInverter board)
2. Ensure OpenInverter board is in tripmode 1 or 2 (In the event of an error, close the precharge contactor and open the main contactor. This helps protect the LDU as 0-"All Off" will kill it for sure if the error happens while its spinning.)
3. For switching 12V power to the OpenInverter board, run two switches in parallel (so both must be turned off to kill the power, so if 1 switch fails somehow, the other still works and the board as 12V)
4. For the negative contactor and main contactor, run two contactors for each in parallel (such that if 1 fails/opens, the other will remain closed. My assumption is that when a contactor fails internally then it opens. I hope that is correct.)
5. Give each contactor its own fuse (lower than the 5a fuse that is feeding the OpenInverter board, so a failure in a contactor doesnt cause the OpenInverter board to loose pwer)
6. Never run a fuse other lower than a 500a pyro fuse (assuming your HV wires are able to handle 500a)

Is the above correct? And is there anything else that can be done?
Should we be running 10kw cooking elements in parallel with both the main and negative contactors?
(My assumption is no as that sounds wacky outside of a bench test situation)

[jrbe]

All that redundancy adds a lot of complication but might not add any protection if they are still switched off accidentally. It's also less safe having 2 switchers to have to turn off. Don't compromise safety for you over saving the inverter.

One thought I had was to have the cabin heater on the inverter side of the contactor. If for some reason the contactor needs to open, the heater could be commanded on and confirmed on before opening the contactor(s).The heater should act as a load dump for at least some left over motor energy. Not sure what motor speeds this would work at. I'm sure at some point the regen will overpower the heater and voltage will jump above what the power section can handle.

The pre charge resistor would likely be overloaded. It also is allowing higher voltage in the motor vs the battery pack through its resistance. I see it as a very short term possible help.

You should be able to force no accel / no decel without shutting down the inverter. Why would someone chose to open the contactor over the no accel / decel besides a big crash?

*Edit*
You fuse to protect the wire and the battery. Size it appropriately. You only need one in the loop unless there's a battery short. 2 at the battery + & - as close to the battery as sensible is ideal for crash safety.

Should only need one oven element in series. It's just a big resistor if something is very wrong but still allows a decent amount of power through for testing.

Fusing the contactors drive lines sounds counterproductive. I'd run them straight off whatever is turning them on. More importantly, verify the economizer is working properly for any contactors. Without these the coils can overheat and might have thermal protection that opens when too hot.
I believe all the open inverter contactor mosfets are switched - side. As long as the grounds are good there should be no issue with the +12v side of things as far as contactor turn on / maintain on is concerned.