Jon Elson writes:

Anyway, after such a long winded description I'm wondering if I could
use 3 xmfrs buck configured to supply power to just the spindle drive.
I have some doubts this is your problem at all. Most VFDs will
handle a wide range of input voltages. I'd check you braking
resistors to be sure they are still working. There is also the
possibility the transistor that turns on the braking resistor
has gone bad. With 22 KVa this must be a pretty big motor and VFD, so
the braking resistor must also be pretty big.


I echo the above.

Can you disable the regeneration and use a {?different} braking
resistor? It's designed to pump power back into the grid vs
waste it; and I suspect your rotary converter does not like it.

Besides, wasting is the good old American way!

Or can you feed the VFD with the single-phase line?