The voltage works against you in this case. A motor that runs on 200V, 50 Hz will be just as happy with 240V, 60 Hz but run faster.
Can you reduce the power demand or raise the voltage somehow? (Changing gears between the compressor and motor, e.g.)
Another idea would be to deactivate the thermostat and run the AC on a timer: With an intervals short enough to give some cooling but not long enough for the motor to burn out.
