Patent ID: 6720792
Filing Date: 2004-04-13
Classification: B60K,B60L,B60W,G01R,H02K,Y02T,Y10S

Abstract:
A device for detecting permanent magnet demagnetization in a motor in a vehicle comprising:a permanent magnet induced voltage monitor that measures a detected permanent magnet induced voltage of the motor at a predetermined speed, wherein the permanent magnet induced voltage monitor has a sensor coil wrapped around a plurality of teeth in a plurality of slots of a stator of the motor adjacent to a rotor of the motor at an edge closest to a gap between the stator and the rotor of the motor, and wherein the sensor coil is not related to a plurality of windings of the motor, and a voltmeter disposed in the vehicle coupled to the sensor coil of the motor, wherein the voltmeter periodically monitors of the state of magnetism of the permanent magnets in the motor during no load conditions to provide the detected permanent magnet induced voltage to a processor; a predetermined irregularity in the motor that cooperates with the sensor coil to locate a position of each of a plurality of permanent magnets in the motor; and a processor that: compares the detected permanent magnet induced voltage with a reference voltage that reflects a permanent magnet induced voltage of the motor with a fully magnetized permanent magnet at the predetermined speed; and analyzes the detected permanent magnet induced voltage with reference to the reference voltage to determine whether a characteristic of the detected permanent magnet induced voltage indicates a demagnetized permanent magnet of the motor.