Investigation of Key Factors Influencing the Response of Permanent Magnet Synchronous Machines to Three-Phase Symmetrical Short-Circuit Faults

Abstract

This paper investigates the three-phase symmetrical short-circuit (SSC) characteristics of a permanent magnet synchronous machine (PMSM). Closed-form solutions are derived to predict both the steady-state and transient response of a PMSM to three-phase SSC faults. The developed expressions account for the impact of prefault operating conditions and include provisions for incorporating magnetic saturation effects. The influences of machine parameters and prefault operating conditions are studied to identify the key factors that have a major influence on the steady-state and peak transient values of the fault currents. It is shown that higher machine characteristic current values, reduced stator resistance, higher q-axis prefault current, and higher magnetic saturation all increase the peak transient value of the demagnetizing d-axis current. Time-stepped finite element (FE) simulation is performed to investigate the rotor demagnetization characteristics of PMSMs under SSC fault conditions. Both two-dimensional (2-D) and three-dimensional (3-D) FE simulations are used to build confidence in the fault current predictions of the developed analytical model, accompanied by experimental verification.