With the development of the rare-earth permanent magnets and their availability on the market the usage of permanent magnet synchronous motors increased. Nowadays this type of motor is commonly used in the electric vehicles. With the development of electric propulsion systems the requirements for quality of their properties have increased and one of them is torque ripple coefficient.
The introduction is a brief overview of the torque ripple and the most commonly used design methods for its elimination.
The second chapter is a summary of operation of a permanent magnet synchronous motor with focus on the dq axis theory of synchronous motor, which is necessary for the understanding of active reduction of torque ripple.
The third chapter describes the »in-wheel« motor developed by the company Elaphe Propulsion Technologies Ltd.. In this chapter, FEMM model of »in-wheel« motor, which is later used in the work for magnetostatic analysis, is explained. The principle of the program analysis of the motor model is also described here.
The fourth chapter describes the torque ripple of the permanent magnet synchronous motor. Torque ripple occurs because of different factors that are described in the subsections.
In the fifth chapter, active reducing of torque ripple is explained. The results of the magnetostatic analysis, calculated with program FEMM, are presented. At the end, we can see the shape of the supply voltage that ensures the constant torque of the motor.