Short-circuit faults in distributed and concentrated windings of PM synchronous motors

For investigation of coil currents, torque and speed pulsation at coil short-circuit faults, an "independent coil" model is set up and presented. The model is based on the calculation of the self and mutual inductances and is implemented in MATLAB/SIMULINK (Matrix operation). Both distributed and concentrated windings are simulated at short circuit faults of different coils. For an x-by-wire application different pole numbers and winding configurations are investigated for the lowest torque pulsation at fault-condition. Moreover, a possible solution for avoiding a disturbing pulsating torque at short-circuit fault is discussed. This method comprises the short-circuit of the coils (or a multiple) constituting the "basic winding scheme".

1. Introduction

In order to predict the behavior of a motor under fault situation, i.e. short-circuit of one or several coils, an “independent coil” model for motors with concentrated windings has been developed [1], [2], [3]. The goal of this paper is to extend the model of [1], [2] to distributed windings so as to obtain a “general independent coil” model (Section 2), allowing the comparison of different three-phase motors regarding their ability to work under fault situations. The model is based on the calculation of the self and mutual inductances and is implemented in MATLAB/SIMULINK. Matrix operation is required in order to build a model which is independent of the number of slots, poles and number of layers per slot. For the comparison process, a PM motor prototype for X-by-wire in automotive application is defined as the reference, which has a concentrated winding with 18 slots and 16 poles, as illustrated in Fig. 1 . All compared motors are assumed to have the same stator lamination geometry with 18 slots. Only the number of rotor poles and the stator winding arrangement may differ. In Section 3, the behavior of these motors, when one or several coils are short-circuited, is compared and studied in order to show their ability of working under fault situation. Section 4 introduces an interesting fault situation on the reference motor: when three consecutive coils of the same phase are short-circuited, no torque and speed pulsation appear at all, for which an explanation is given. Fig. 1: Reference PM motor with concentrated winding, 16 poles 18 slots.