What will happen if you attach the negative pole of welder to the rotor of the motor or the body , will that cause problem?

Question

I have built a machine that rotates a cylinder to weld it, I have to attache a negative pole to the cylinder which is connected directly to the rotor of motor, the motor is controled by a vfd , will that cause any issue to motor and vfd or not?

Answer 1

Most likely, yes, it will cause a problem. You need to isolate the VFD and motor away from the rotating cylinder or the welder will cause issues.