Control scheme for fault tolerant converter topology based dual channel permanent magnet motor drive system

An electric motor system comprising:

• a control circuit;
• a motor drive system;
• a motor that comprises a rotor having a magnet mounted thereto and a stator that comprises one or more motor phase windings connected to the motor drive system to allow the motor drive system to drive rotation of the rotor;
• wherein the motor drive system comprises two channels, each channel comprising a respective power inverter that can be controlled to provide torque for driving rotation of the rotor, and wherein in the event of a one switch short circuit (OSSC) fault affecting the power inverter in one of the channels, the power inverter in that channel is operable to produce intermittent assistive torque using the remaining switches;
• wherein the electric motor system is configured such that:
• when it is determined that one of the channels of the motor drive system has a OSSC fault:
• during a start-up operation of the motor system, wherein the rotor is to be driven from standstill to a continuous rotation the control circuit is configured to:
• determine whether or not the initial angular position of the rotor at standstill falls within a range of angles where the channel of the motor drive system that has the OSSC fault can provide assistive torque;
• and
• when it is determined that the initial angular position of the rotor does not fall within a range of angles where the channel of the motor drive system that has the OSSC fault can provide assistive torque, the control circuit is operable to control the motor drive system to move the rotor so that the angular position of the rotor falls within a range of angles where the channel of the motor drive system that has the OSSC fault can provide assistive torque, and then once the rotor is moved to an angular position where the channel of the motor drive system that has the OSSC fault can provide assistive torque, the control circuit then controls the motor drive system to use both channels to start driving continuous forward rotation of the rotor.