Abstract
A motor variator and a driving method thereof are provided for controlling the operating speed of a fan, which employ an alternate current chopper to change the working cycle and the rotary speed of a stepless motor. The motor variator includes a high-frequency alternate current chopper connected to an induction coil of an induction motor, an alternate current power supply connected to the high-frequency alternate current chopper and a controller connected to the high-frequency alternate current chopper for outputting a switch signal to the high-frequency alternate current chopper, such that the high-frequency alternate current chopper is controlled by the switch signal to perform a chopper action for the alternate current power supply and output a drive voltage, so as to change the rotary speed of the induction motor.