Thanks Terry
Yes it is same thread, I'm working on a complicated DC controller boards using IGBTs and boards keep blowing up, while on other machine having same system the factory engineer replaced DC motors with 2 AC motors and put a 300$ inverter (3.5 hourse power) to control the 2 parallel motors which they drive same load, and it seems to be ok for now, but I'm not very comfortable with it.
Motors are quite small, I didn't check because it is not my work but I guess it will be about 1.5 hp each.
Regards
Mahmood