Patent ID: 9590552
Date: 2017-03-07
CPC Classifications: H02P

Claim:
1. A motor drive device that drives a multi-phase synchronous motor in an electric compressor, the multi-phase synchronous motor including a rotor having a permanent magnet and a stator having coils of different phases, the motor drive device comprising: an inverter that supplies current to the coils; and a control unit that controls the inverter, wherein the control unit executes: an initial angular position calculation processing including detecting a d-axis and a q-axis of the rotor as an initial angular position of the rotor based on a current flowing in response to a voltage pulse applied to the coils of the stator; a rotating processing including rotating the d-axis and the q-axis of the rotor by a predetermined angle θa in a direction opposite to rotation of the rotor; an acceleration processing including accelerating the rotation of the rotor by rotating the rotated d-axis and the rotated q-axis in the rotating direction of the rotor and flowing through the stator the torque component current determined based on a d-axis and a q-axis; and a sensorless control processing including controlling the rotation of the rotor based on an angular position and a speed of the rotor estimated based on the voltage applied to or the current flowing through the coils after an angular velocity of the rotor has reached a predetermined speed by executing the acceleration processing, wherein the predetermined angle θa is determined based on an initial target of a d-axis and an initial target of a q-axis of the sensorless control processing.