Fault shutdown control of an electric machine in a vehicle or other dc-powered torque system

A vehicle comprising:

• a direct current (DC) power supply;
• a set of road wheels;
• a three-phase electric machine having an output shaft operable for transmitting an output torque to the set of road wheels to thereby drive the road wheels and propel the vehicle;
• a contactor pair;
• a DC voltage bus;
• an alternating current (AC) voltage bus;
• a power inverter module (PIM) having a plurality of semiconductor switches, wherein the PIM is selectively connected to the DC power supply via the DC voltage bus and the contactor pair, and is directly connected to the electric machine via the AC voltage bus;
• and
• a controller programmed to execute a control action with respect to the torque system in response to a predetermined fault condition, wherein the predetermined fault condition results in an opening of the contactor pair and a three-phase short condition, the control action including:
• calculating a back electromotive force of the electric machine;
• and
• transmitting switching control signals to the semiconductor switches to transition from the three-phase short condition to a three-phase open condition only when the calculated back electromotive force is less than a calibrated value and a voltage rise on a DC side of the PIM is less than a calibrated voltage rise.

A method of controlling a direct current (DC)-powered torque system in response to a predetermined fault condition, wherein the torque system includes a DC power supply, a power inverter module (PIM) connected to the DC power supply via a contactor pair and a DC bus, and an electric machine connected to the PIM via an AC bus, and wherein the predetermined fault condition is a fault resulting in an opening of the contactor pair and a three-phase short condition, the method comprising:

• detecting the predetermined fault condition via a controller;
• calculating a back electromotive force of the electric machine;
• and
• transmitting switching control signals from the controller to a plurality of semiconductor switches of the PIM to thereby transition from the three-phase short condition to a three-phase open condition only when the calculated back electromotive force is less than a calibrated value and a voltage rise on a DC side of the PIM is less than a calibrated voltage rise.