Design of a permanent magnet brushless DC motor for the electric three-wheeler in Bangladesh

Abstract

The design of a 1 KW PM BLDC motor for compact-sized electric three-wheelers (C-E3Ws) has been presented here. The C-E3Ws primarily operate in the cities, especially Dhaka, and they are more suitable for congested city roads than other E3W variants. Few works have been reported on the design of PM-BLDC motors for E3Ws. However, none of them addressed the BLDC motor's performance in C-E3Ws. This work addresses this research gap. Three real-time driving profiles of C-E3Ws have been recorded from three different areas of Dhaka City. These driving profiles have been analyzed to determine the prospective motor peak torque, rated speed, and continuous torque region for the motor design. The primary motor design goals have been set based on motor efficiency, speed, and torque. A mathematical equation-based analytical sizing model has been developed for the motor design. Practically measurable parameters are chosen from a commercial C-E3W motor, and others are selected for effective design consideration. A 2-D finite element (FE) based electromagnetic model of the PM-BLDC motor has been developed in Ansys Maxwell with the values obtained from the analytical sizing model, which is optimized to achieve the design goals. The magnet dimensions and motor stack length are considered as the optimized design variables. From FE analysis, motor torque and different types of losses are determined. The results show that the designed motor has achieved the design targets. A lumped parameter-based thermal model has been developed in Ansys Motor-CAD to evaluate the motor's thermal performance over the recorded driving profiles and the motor's continuous operation region. The necessary parameters are appropriately calibrated for the thermal analysis. The performance of a commercial C-E3W motor is evaluated with experimental set-up and compared with the designed BLDC motor. The designed PM-BLDC motor displays better performance in terms of efficiency and power factor than its commercial counterpart.