Control strategy of a dual lane fault tolerant permanent magnet motor to reduce drag torque under fault condition

A method of controlling a motor drive circuit for driving a dual lane fault tolerant permanent magnet motor, the method comprising:

• monitoring the motor speed of the dual lane fault tolerant permanent magnet motor;
• detecting when a switch short circuit occurs in any switch in any of two inverters connected to the dual lane fault tolerant permanent magnet motor;
• comparing the motor speed to a predetermined threshold;
• short-circuiting all motor phases of a the dual lane fault tolerant motor connected to the inverter in response to detection of both:
• i) a switch short circuit in any switch in the inverter, and ii) the motor speed exceeding a predetermined threshold;
• and
• not short-circuiting any motor phases not containing the short-circuited switch if the motor speed does not exceed the predetermined threshold.