Patent ID: 8314577

Claim:
An electromechanical apparatus comprising: magnetic coils of N phases (N is an integer of 3 or more); magnets; and a PWM drive circuit that drives the magnetic coils of N phases, wherein the magnetic coil of each phase can be independently controlled by the PWM drive circuit, the PWM drive circuit drives all the magnetic coils of N phases at a starting time and, after the starting, selects the number of phases to be driven in accordance with the magnitude of torque required for the electromechanical apparatus, a control unit that controls voltage to be applied to the magnetic coil, wherein the control unit applies voltage to the magnetic coil in an excitation interval that is symmetric about a π/2 phase point when a position at which the polarity of a waveform of induced voltage induced in the magnetic coil due to the movement of the magnets is reversed is defined as a π phase point, does not apply voltage to the magnetic coil in a non-excitation interval that is symmetric about the π phase point of the waveform of the induced voltage, and makes the length of the non-excitation interval greater as the electromechanical apparatus rotates at high revolution.