Patent ID: 9660560
Date: 2017-05-23
CPC Classifications: H02P

Claim:
1. A drive system for a brushless DC motor having a rotor including at least one permanent magnet and a stator including at least one phase winding, the drive system comprising: a drive circuit including switch means associated with the winding for varying current passing through the winding; rotor position sensing means arranged to sense the position of the rotor; and control means arranged to provide drive signals to control the switch means; the drive circuit further being arranged to receive a temperature signal that has a value dependent upon the temperature of the at least one magnet of the rotor, characterized in that the control means is arranged to vary the phase of the current passing through the winding relative to the rotor position dependent upon the temperature of the rotor magnet by controlling the motor in a normal mode when the temperature of the rotor magnet is below a predetermined temperature and in an abnormal mode when the temperature of the rotor magnet is above the predetermined temperature.