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.

Keywords

• Active short-circuit
• cross saturation
• demagnetization
• direct flux-vector control
• PMSM