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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.

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Purpose – The purpose of this paper is to obtain an integrated method for inter-turn short circuit fault detection for the cage-rotor induction machine (CRIM) considering saturation effect. Design/methodology/approach – The magnetic equivalent circuit (MEC) is proposed for machine modeling and nonlinear B-H curve is considered for saturation effect. The machine has some differential equations which are converted to algebraic type by trapezoidal method. On the other hand, some nonlinear equations are present due to saturation effect. A set of nonlinear algebraic equation should be solved by numerical method. Therefore, the Newton-Raphson technique is used for equation solving during of the considered time step. Findings – Generally, the operating point of electrical machines is close to the saturation zone due to designing considerations. Moreover, some current and torque harmonics will be produced due to time and space harmonics combination, which cannot be studied when saturation modeling is neglected. Considering both space and time harmonics, a method is proposed for inter-turn short circuit fault detection based on the stator current signatures and the machine performance is analyzed in healthy and faulty cases. In order to obtain the integrated method, two sample machines (two and also four-pole machines) are modeled and finally the accuracy of the proposed method is verified through the experimental results. Research limitations/implications – The calculations have been done in this work is limited to CRIM considering. However, the presented modeling method can be used for another types of electrical machines by some minor modifications. Originality/value – Obtaining of an integrated formula for the inter-turn short circuit fault detection which has been presented for first time is the more advantages of present work. Moreover, in order to saturation effect considering, a new method is presented for solving of nonlinear equations which is another novelty of paper.