Design And Field-Weakening Control Of EV-Used PM Motor

As one of the core components of electric vehicles(EV), permanent magnet (PM) motor have a significant impact on the EV operation performance. Therefore, design of high-efficiency, high-reliability and superior-controllability motors is rather important. In this thesis, a high power density, high efficiency and wide speed range PM motor is designed in this paper, whilst its field-weakening control is investigated.Firstly, the interior V-shaped rotor is used in the EV PM motor, which has a rated power of20kW and rated speed of2000r/min. The basic design methodology and the structure selection criteria of the PM motor main are presented. With finite element analysis (FEA), optimal design of the rotor slots are carried out in order to reduce the cogging torque. Influence of the distance between the magnet poles on the parameters of electromotive force (EMF) and air gap flux density is studied, so as to find out the design rules of the V-shaped rotor slots. Moreover, the influence of the poles distance on the electromagnetic torque and torque ripple is also investigated when the maximum torque per ampere is realized and both rated and two times rated current are fed in the armature windings, respectively. By analyzing the no-load EMF the winding self-inductance and mutual-inductance harmonics, their impact on the motor torque ripple is revealed. Furthermore, finite element software Abaqus is used to analyze the stress field when the motor is running at the rated speed, to determine the maximum stress points and the resultant deformation of rotor lamination stack.Field-weakening control is a main strategy for EV. In this thesis, Matlab/Simulink software is used, and the field-weakening control system is designed and studied in order to implement speed extension of the motor.A prototype is built and its measured parameters and experiment results are given.