now I'm working on a project which involves a dc motor and high voltage. I'm developing a machine consists of a motor to rotate a platform disc and high voltage will be applied during the rotation. The problem is when I supply a positive high voltage at motor shaft during rotation, the motor stop working. Do you guys have any idea, how I can supply the high voltage properly the high voltage supply?
Don't apply the high voltage to the motor shaft, isolate the disc and only apply the high voltage to that.
Edit based on comments:
isolate ie insulate, electrically separate the disc from the motor shaft while keeping the mechanical drive to make it rotate. Slip rings can be used to apply the voltage to the, now insulated, disc.
See here for an explanation of slip rings: https://en.wikipedia.org/wiki/Slip_ring