Patent ID: 8860356
Filing Date: 2014-10-14
Classification: B60L,H02K,H02P,Y02T

Abstract:
1. A motor drive system comprising: an inverter for driving a motor having a rotor in which a low-coercive permanent magnet is embedded; a rotation angle sensor for detecting a rotation angle of the rotor; a boost circuit for boosting a DC voltage, to be supplied to the inverter, from a first voltage value to a second voltage value so as to vary magnetic flux of the low-coercive permanent magnet; and a controller for controlling the boost circuit to boost the DC voltage value to the second voltage value when varying the magnetic flux of the low-coercive permanent magnet, and controlling the inverter to generate magnetization current when boosting the DC voltage value to the second voltage value is completed, wherein the controller calculates a rotation speed of the rotor based on the rotation angle, calculates a magnetization current value for the magnetization current based on a target value of magnetic flux for a present magnetic flux of the low-coercive permanent magnet existing when the magnetic flux of the low-coercive permanent magnet is to be varied, and sets the second voltage value by referring to a table, in which a plurality of voltage values corresponding to plural stored sets of magnetization current values and rotation speeds, using the calculated magnetization current value and the calculated rotation speed.