Guaranteed Torque and Demagnetization Current During Active Short-Circuit Transients of PMSMs

Active short-circuit is a standard emergency procedure applied to three-phase permanent-magnet synchronous machine drives in battery-electric and hybrid electric drivetrains to comply with stringent automotive safety standards, such as the ISO 26262. Unfortunately, the ensuing torque and current transients can harm the passengers and the driveline itself. This paper develops and validates a mathematical and graphical method to determine the safe operating area of pre-fault current conditions to guarantee that the torque remains within user-defined acceptable bounds and that the permanent magnets do not demagnetize during the short-circuit transient. The new method utilizes an inductance-based dynamic model of the motor, including magnetic saturation. The proposed methodology promises to be useful in the design, initial testing, and commissioning of permanent-magnet synchronous machines used for the propulsion of automobiles.