Study on the Slotless PM Motor Design Process Considering High Speed

Slotless-type motors have a very constant torque without cogging torque because the windings are arranged in the gap of the stator. In addition, since there is no stator teeth structure, reduces harmonic generation, and the eddy current loss of the permanent magnet and iron loss are small, resulting in high efficiency. However, slotless motors generate large current harmonics due to their low inductance when pulsewidth modulation (PWM) control is considered. Large current harmonics affect torque ripple and voltage THD, resulting in reduced motor performance. Therefore, additional inductance is required for slotless motors. In this article, the process for the detailed design of slotless-type motors and determining the inductance through PWM analysis is proposed. A detailed design technique for a slotless motor that satisfies the target performance and limitations was presented. In addition, PWM control was implemented using MATLAB’s Simulink to determine the accurate inductance. The validity of the proposed process is verified by finite element analysis (FEM) using PWM control.