Patent ID: 8581533
Filing Date: 2013-11-12
Classification: H02P

Abstract:
1. A motor driver that receives electric power supply from a power source to drive a permanent magnet motor, the motor driver comprising: an inverter that includes a switching device and performs electric power conversion between the power source and the permanent magnet motor; and a controller that controls switching of the switching device according to a desired output of the permanent magnet motor, wherein the controller includes: a magnet temperature detection device that detects a magnet temperature of the permanent magnet motor; a setting device that sets a threshold value of the magnet temperature corresponding to the desired output of the permanent magnet motor, based on a predetermined relation between an output from the permanent magnet motor and a critical temperature, up to which demagnetization in the permanent magnet motor is not caused; and a carrier frequency control device that, when the magnet temperature detected by the magnet temperature detection device exceeds the threshold value, changes a carrier frequency, at which the switching device is switched, in such a manner that a ripple current superimposed on a motor current that flows through the permanent magnet motor is reduced.