Patent ID: 7960930

Claim:
A control apparatus for a motor drive system including an inverter that drives an alternating-current motor, comprising: a current detector that detects a motor current flowing to the alternating-current motor; a position detector that detects a rotational position of the alternating-current motor; a control mode selection device that selects a control mode for voltage conversion performed in the inverter based on an operating state of the alternating-current motor; a first motor control device that performs, when the control mode selection device selects a first control mode, in which a rectangular-wave voltage is applied to the alternating-current motor, torque control by performing feedback control, in which a phase of the rectangular-wave voltage is adjusted based on a deviation of a torque output from the alternating-current motor (M 1 ) from a torque command value; and a second motor control device that performs, when the control mode selection device selects a second control mode, in which a voltage applied to the alternating-current motor is controlled in a pulse-width modulation mode, torque control by performing feedback control on the motor current based on a current command value corresponding to the torque command value, wherein the first motor control device includes: a first torque estimation device that estimates the torque output from the alternating-current motor based on outputs from the current detector and the position detector; a voltage phase control device that determines the phase of the rectangular-wave voltage based on a deviation of the torque estimated by the first torque estimation device from the torque command value; and a first voltage control device that controls voltage conversion performed in the inverter so that the rectangular-wave voltage with the phase determined by the voltage phase control device is applied to the alternating-current motor, and the second motor control device performs the feedback control on the motor current based on the outputs from the current detector and the position detector.