Patent ID: 9088238
Filing Date: 2015-07-21
Classification: H02P

Abstract:
1. A method of determining the position of a rotor of a permanent-magnet motor, the method comprising employing a first scheme to determine the position of the rotor when rotating within a first speed range and employing a second scheme to determine the position of the rotor when rotating within a second speed range, wherein the first scheme comprises: sequentially exciting and freewheeling a winding of the motor; measuring a parameter that depends on the rate of change of current in the winding during excitation or freewheeling; comparing the measured parameter against a threshold; and determining that the rotor is at a predetermined position when the measured parameter is less than or greater than the threshold, and the second scheme comprises: generating a signal having a voltage that is proportional to the voltage across the winding; generating a further signal having a voltage that depends on the rate of change of current in the winding; comparing the voltages of the signal and the further signal; and determining that the rotor is at a predetermined position when the voltage of the signal corresponds to the voltage of the further signal.