FEM Analysis of Brushless DC Servomotor with Fractional Number of Slots per Pole

Abstract

The authors present in this paper the analysis with Finite Element Method (FEM) of the magnetic circuit for a Brushless DC servomotor with fractional number of slots/pole (9 slots and 10 poles). For this purpose, FEMM 4.2 software package was used for the analysis. To obtain the waveforms of Back-ElectroMotive Forces (BEMFs), electromagnetic and cogging torque for servomotor a program in LUA scripting language (integrated into interactive shell of FEMM4.2) has been created. A comparation with a structure with integer number of slots/pole (18 slots and 6 poles) was also realized. The analysis results prove that the structure chosen is an optimal solution: sinusoidal waveforms of BEMFs, improved electromagnetic torque and reduced cogging torque. Therefore, the operating characteristics of the servomotor with 9/10 slots/poles manufactured by Sistem Euroteh Company and included in an integrated electrical drives system are presented in this paper.

Keywords

• permanent magnet motors
• brushless motors
• finite element methods