Magnetic-equivalent-circuit approach for inter-turn and demagnetisation faults analysis in surface mounted permanent-magnet synchronous machines using pole specific search-coil technique

Abstract

Magnetic-equivalent-circuit model for surface mounted permanent-magnet synchronous machines in both healthy and faulty cases is presented in this study, where both saturation effect and space harmonics are considered. Pole numbers, magnets and slot numbers can be chosen arbitrarily in the proposed model, and the behavior of the machine can be studied under various kinds of faults by a single model. Demagnetization, as well as inter-turn short short-circuit faults of the stator windings, are modelled, and a fault detection method is proposed. It is shown that the demagnetization fault is not detectible by stator current analysis, therefore an additional pole specific coil is considered in this study as a search coil. For modelling, the differential equations representing the electrical part of the PMSM model are converted into an algebraic type using the wellknown trapezoidal technique and are solved simultaneously together with the non-linear magnetic equations using the Newton- Raphson method. It is shown that the presented model in this study is capable of effective modelling of the healthy and faulty machine under mentioned faults by a single model, thus reducing the computational complexity of the model. The effectiveness of the proposed MEC model is verified using finite-element method via Maxwell software.