Active Short-Circuit Strategy for PMSMs Enabling Bounded Transient Torque and Demagnetization Current

Abstract

The active short-circuit is a standard safety measure for permanent-magnet synchronous machine drives in electric vehicles, but it can lead to harmful torque and current transients. This paper introduces a mathematical and graphical method to determine the safe operating area of pre-fault current conditions, complying with user-defined torque bounds and preventing magnet demagnetization during short-circuit transients. The method incorporates an inductance-based motor model considering magnetic saturation, which is used to outline a strategy for transitioning to safe initial conditions in the minimum time for the available voltage. Experiments on a 35-kW permanent-magnet synchronous machine support the efficacy of the proposed strategy, offering promise for its use in automotive propulsion where compliance to safety standards such as the ISO 26262 is paramount.