Patent ID: 8497648

Claim:
A synchronous motor drive system, comprising: three-phase inverters each operable to convert a direct current to a three-phase alternating current; a current application control unit operable to control operations of the three-phase inverters; and a synchronous motor operable to drive by the three-phase alternating currents supplied from the three-phase inverters, wherein the synchronous motor includes: three-phase coil groups each supplied with a three-phase alternating current from one of the inverters; a rotor that has magnetic poles distributed circumferentially along a rotation direction of the rotor at equal intervals; and a stator on which stator coils are arranged circumferentially along the rotation direction of the rotor, each stator coil wound by concentrated winding and belonging to one of the three-phase coil groups, wherein every M consecutive stator coils belong to one of stator coil groups arranged at equal intervals, M being an integer two or greater, at least two consecutive stator coils in each stator coil group are arranged at an interval different from the intervals of the magnetic poles of the rotor and belong to different three-phase coil groups, the current application control unit determines, for each three-phase inverter, a current phase angle and a current amount of a three-phase alternating current to output so as to control at least one of the three-phase inverters to operate in a first current application mode and control at least another one of the three-phase inverters to operate in a second current application mode, the first current application mode being a mode in which the three-phase inverters generate a three-phase alternating current having a sinusoidal waveform, the second current application mode being a mode in which the three-phase inverters generate a three-phase alternating current having a step waveform with polarity alternating before and after part of a period of 2π electric radians, supply the three-phase alternating current except during the part, and do not supply the three-phase alternating current during the part, and each inverter supplies a three-phase alternating current having the determined current phase angle and current amount to a different one of the three-phase coil groups.