Patent ID: 6605912
Filing Date: 2003-08-12
Classification: H02P

Abstract:
A method of controlling operation of a permanent magnet motor, comprising:selecting a mode of operation from first, second and third modes of operation based on at least one of a signal indicative of a parameter of the motor and a command signal wherein the first and second modes of operation are constant torque modes and the third mode of operation is a field weakening mode; applying to the motor, phase currents which are substantially in phase with corresponding electromotive forces of the motor when the first mode of operation is selected; applying to the motor, phase currents which are substantially sinusoidal and are substantially in phase with corresponding electromotive forces of the motor when the second mode of operation is selected wherein the second mode of operation is selected from the first mode of operation when a load current exceeds a preset value; and applying to the motor, phase currents which are substantially out of phase with corresponding electromotive forces of the motor when the third mode of operation is selected; wherein the said permanent magnet motor comprises a permanent magnet brushless direct current motor having a trapezoidal distribution of magnetic field in an airgap thereof.