Study on Winding Method and Mechanical-electronic Design for High-speed Operation of Electric Motor

Abstract

In response to the tightening of environmental regulations due to climate change and the gradual depletion of fossil fuel resources, the automobile industry is accelerating the transition from conventional internal combustion engine systems to high-efficiency, low-carbon electric drive systems. This shift applies not only to passenger cars but also to high-performance vehicles such as sports cars. In high-performance electric vehicles that employ a fixed gear ratio, the drive motor’s rotational speed is directly linked to the vehicle’s wheel speed. Therefore, a high-speed motor design is essential to expand the vehicle’s driving speed range. In this study, we conducted a detailed analysis of a commercial model from a leading manufacturer capable of operating at over 20,000 RPM to derive its input/output characteristics. Based on this analysis, we designed a drive motor capable of achieving even higher speeds under the same output conditions. The number of poles was selected to ensure sufficient control resolution within the limited switching frequency of the insulated-gate bipolar transistor (IGBT) elements during high-speed operation. Additionally, the optimal winding type for high-speed driving was determined by comparing the AC loss characteristics of hairpin windings with a round-wire model using parallel strands. To ensure mechanical reliability, the rotor design was optimized to reduce stress during high-speed operation. To validate the proposed motor design, efficiency maps were generated across the full driving range to assess output characteristics. Finally, a prototype was fabricated and tested to confirm the validity of the design.