I have had 2 VFDs on the same piece of equipment go bad by an apparent
line to line short circuit. It destroyed the line contactor, tripped the motor circuit breaker, the feed circuit breaker, and the main circuit breaker feeding the panel. Motor was meggered line to line, and line to ground with no bad readings. It is now running fine in bypass mode.
Any help would greatly be appreciated.
It sure sounds like you need a line reactor on that setup.
Does this load cycle frequently?
Do you stop the load by sending the stop command to the VFD, or opening the line side contactor?
Here's a good read on line and load reactor basics - https://precisionautomation.net/2019/05/11/line-and-load-reactors-basics/