Numerical Analysis of Turn-to-Turn Short Circuit Current Mitigation for Concentrated Winding Permanent Magnet Machines With Series and Parallel Connected Windings

Due to its high power density, the fractional slot concentrated winding permanent magnet synchronous machine (PMSM) is a competitive candidate for the aircraft starter generator (SG) system. However, the short circuit (SC) fault, especially the turn-to-turn SC fault, is the obstruct crux in aviation applications. The turn-to-turn SC current can be restricted to a permissible level with higher reactance and the current injection mitigation method. However, higher self-inductance always leads to lower power density. So far, there have been no numerical criteria for the tradeoff between the two characteristics in machine design. In this article, an analytical model based on flux distribution is used to estimate the SC current. The effectiveness of the d-axis current injection mitigation method is numerically analyzed in the series and parallel connected windings individually. The requirement for PMSMs to survive the turn-to-turn SC fault is derived. The mathematical analysis is verified by finite-element analysis and experiments on a 12-slot, 10-pole PMSM. This article provides theoretical support for designing high-performance permanent magnet starter generator (PMSG) with SC current mitigation ability for the aviation power system.

I. Introduction

Fractional slot concentrated winding (FSCW) permanent magnet synchronous machines (PMSMs) are characterized by high torque and power density. Their appealing properties of fault tolerance in response to open circuit faults and terminal short circuit (SC) faults make them very competitive in the aircraft starter generator (SG) applications [1], [2]. However, the turn-to-turn SC current still remains excessively high in the FSCW-PMSM. If left uncontrolled, the heat generated by the SC current can threaten the operation of the machine, even the safety of the system.