Finite Element Analysis of Healthy and Faulty Permanent Magnet Synchronous Motors used in Hybrid Vehicles Jawad Faiz, H. Nejadi-Koti and Mehran Keravand Center of Excellence on Applied Electromagnetic Systems, School of Electrical and Computer Engineering, College of Engineering, University of Tehran, Tehran, Iran. Abstract- Precise simulation of permanent magnet synchronous motors (PMSM) is the most important part in many cases particularly in their fault diagnosis and optimal control. This paper introduces different simulation methods of PMSM where finite elements method (FEM) is chosen as computation tools. The logic and problem solving is investigated and positive and negative points are described. Then, the trend of simulation using FEM is explained and a PMSM used in hybrid vehicles is simulated under healthy and faulty conditions and the results are discussed. Finally, short circuit fault in a PMSM is diagnosed using the stator phase currents. I. INTRODUCTION Attempt has been made to introduce efficient solutions for energy crisis and greenhouse phenomenon. Considerable fossil fuels are consumed in road transportation and it is possible to solve the proposed problems by managing and modifying them. Hybrid and electric vehicles are substitution to traditional cars which can reduce the environmental pollution. Hybrid vehicles have both electric motor and combustion engine operating beside each other harmoniously. In order to be able to compete in the car market, the hybrid cars must be strengthened in several aspects; the most important one is their reliability. Most users of the hybrid vehicles are the ordinary peoples and do not have enough knowledge about electric motors. On the other hand, failure of electric motor with no warning to the user can lead to many problems. Fault occurrence in the motors used in the hybrid vehicles can even injure the users. So, the cost of fault diagnosis in the motors used in the hybrid vehicles has second priority. First and most important stage in designing fault diagnosis systems and introducing a convenient index for any fault diagnosis of the electric motor used in the hybrid vehicle is the choice of a suitable and precise method for electric motor modeling [1, 2]. So far, different methods have been introduced for modeling and simulating permanent magnet synchronous motor (PMSM). Winding function and magnetic equivalent circuit methods are two comprehensive techniques applied to PMSM as described in [3-12]. Finite element method (FEM) is the most precise technique which can be used for modeling and analyzing this motor. The FEM is a numerical method based on the geometry and windings of the motor. This modeling method uses optimal numerical computation algorithms such as regressive Euler and Runge- Kutta in order to obtain the magnetic field in different parts of the motor. Motor performance description is obtained through a very thin meshing of the motor and then magnetic field distribution of each part is obtained. The FEM has been applied for simulation of PMSM under demagnetization fault [13-19], inter-turn fault [20-25] and eccentricity fault [26-31]. Comprehensive review of demagnetization and inter-turn fault diagnosis indexes applied to PM machines is presented in [32- 33]. It is noted that the FEM computations results can be used for verification of the results of other modeling methods. The procedure for proposing and solving a problem is the distinguishing feature of FEM. In analytical method, the magnetic equivalent circuit of the motor is considered and differential equations of the machine are written using Kirchhoff's voltage law (KVL) and Kirchhoff's current law (KCL), then by solving these equations, variables are determined. In the next stage, these quantities are used to estimate the magnetic flux within the motor. However, FEM solves the magnetic field equations within the motor and this can be used to obtain other quantities of the motor such as air gap magnetic flux density, windings inductances, induced back-electromotive force (EMF), stator current and the developed torque. This paper reviews various steps in simulating an electrical motor and then modeling a healthy PMSM based of 2D-FEM. Then, a faulty case is modeled for the proposed motor. The healthy and faulty motor is simulated and diagnosis procedure for inter-turn fault of PMSM is introduced. Section VI concludes the paper. II. MODELING OF A HEALTHY PMSM USING FEM A healthy PMSM used in a hybrid vehicle is modeled here. Specifications of this motor are given in Table 1. In the simulation, different stages are followed as described in the following sections. A. Two- and Three-dimensional Simulation of Motor The motor can be simulated in two-dimensional (2D) assuming axial symmetry and/or three-dimensional (3D) in more general cases. In the 3D simulation, the whole actual ＹＷＸＭＱＭＵＰＹＰＭＴＴＸＹＭＴＯＱＷＯＤＳＱＮＰＰ＠ﾩＲＰＱＷ＠ｉｅｅｅ ＴＱＴ