Patent ID: 7315147
Filing Date: 2008-01-01
Classification: H02P

Abstract:
1. A drive system of an AC motor having a plurality of coil pairs and a permanent magnet, one of said coil pairs being positioned to have phase difference from the other and said permanent magnet being constituted such that a plurality of polar elements are disposed to become alternating opposite poles, said drive system comprising: a first phase sensor constituted to detect a magnetic field generated by one of said coil pairs to produce a sinusoidal voltage waveform that is identical to a back electromotive force waveform of said one of said coil pairs; a second phase sensor constituted to detect a magnetic field generated by the other of said coil pairs to produce a sinusoidal voltage waveform that is identical to a back electromotive force waveform of the other of said coil pairs; rotation detection means constituted to detect a direction of rotation of said AC motor; a rotation control circuit constituted to reverse a polarity of either of the sinusoidal voltage waveforms detected by said first and second phase sensors depending on the direction of rotation of said AC motor; and an amplifier constituted to provide each of said coil pairs with electric current of the voltage waveform reversed by said rotation control circuit according to the direction of rotation of said AC motor, wherein said rotation control circuit respectively provides rectangular waveforms respectively converted from the sinusoidal voltage waveforms generated by said first and second phase sensors until a rotation speed of said AC motor exceeds a prescribed value, wherein said rotation control circuit respectively provides each of the sinusoidal voltage waveforms generated by said first and second phase sensors when the rotation speed of said AC motor exceeds the prescribed value.