To improve precision in zero point correction of resolver of a polyphase motor.
When a first DC current is supplied to coils of a three-phase motor in a first energization (steps S2 to S4), rotation of the motor is locked at either of a plurality of electrical angles (180° or 0°) where torque becomes zero. When a second DC current is subsequently supplied to the coils of the motor in a second energization (steps S5 to S6), rotation of the motor is locked at an prescribed electrical angle (210°) where the torque becomes zero. The electrical angle appearing when the second energization is started is assured to be either of 180° or 0° by performing the second energization after the first energization, so that the motor is surely locked at the electrical angle of 210°, even if there is an electrical angle (30°) where torque becomes zero in addition to the electrical angle of 210°. Thus, the zero point of the resolver can be precisely corrected by comparing the electrical angle of 210° with output of the resolver.
TAKAGI MASANORI
TSURUMIYA OSAMU
NAKANO YASUHIRO
HORII HIROAKI
MORISHITA FUMIHIRO
Kazuaki Niki
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