Maximization of High-Efficiency Operating Range of Spoke-Type PM E-Bike Motor by Optimization Through New Motor Constant

This work focuses on maximizing the high-efficiency operating range of a spoke-type permanent magnet (PM) motor by minimizing losses with a proposed motor constant to extend the cruise range for E-bikes. Multiple factors are usually involved in reducing copper and iron losses, and the efficiency may not be easily manipulated in the design processes for high-performance motors. The motor efficiency may directly be obtained through simulations upon completion of designs, resulting in a long product development period. Therefore, this paper proposes a simple optimization method covering copper and iron losses to expand motor high-efficiency ranges. A 300 W spoke-type PM motor for E-bikes is used as the target. The torque density is enhanced and the power losses are minimized based on the proposed new motor constant, which is developed to comprehensively evaluate motor performance and efficiency. The Genetic Algorithm is used in conjunction with the new motor constant to maximize the high-efficiency operating range. The analysis results reveal that the optimized spoke-type PM motors can achieve a higher torque density and broader high-efficiency range than that without being optimized. A prototype is fabricated, and experiments are conducted to validate the analysis.