Optimal Design Considering AC Copper Loss of Traction Motor Applied HSFF Coil for Improving Electric Bus Fuel Economy

Kyoung-Soo Cha, Young-Hoon Jung, Soo-Hwan Park () and Min-Ro Park ()
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Kyoung-Soo Cha: Advanced Mobility System Group, Korea Institute of Industrial Technology, Daegu 42994, Republic of Korea
Young-Hoon Jung: Department of Automotive Engineering, Yeungnam University, Gyeongsan 38541, Republic of Korea
Soo-Hwan Park: Department of Mechanical, Robotics, and Energy Engineering, Dongguk University, Seoul 04620, Republic of Korea
Min-Ro Park: Department of Electrical Engineering, Soonchunhyang University, Asan 31538, Republic of Korea

Mathematics, 2025, vol. 13, issue 9, 1-21

Abstract: Improving the fuel economy of electric buses requires traction motors that provide not only high-power density but also high efficiency under diverse driving conditions. While high slot fill factor (HSFF) coils such as the maximum slot occupation (MSO) coil improve motor torque and power density, they inevitably increase AC copper losses due to elevated AC resistance, especially at high speeds. Unlike conventional motor optimization studies that mainly focus on efficiency at specific operating points, this paper proposes a drive-cycle-aware design optimization method that minimizes AC copper loss to enhance real-world fuel economy. By combining 2D finite element analysis (FEA) with vehicle-level simulations under three representative driving cycles (Manhattan, HWFET, HDUDDS), an optimal motor design was derived. The optimized motor achieved improvements in fuel economy by 0.20%, 0.86%, and 0.36%, respectively, compared to the initial design. Experimental validation through prototype fabrication confirmed the effectiveness of the proposed method. These results demonstrate that the proposed design approach can contribute to improving energy efficiency and reducing operational costs in electric bus applications.

Keywords: AC copper loss; electric bus; fuel economy; optimal design; traction motor; vehicle simulation (search for similar items in EconPapers)
JEL-codes: C (search for similar items in EconPapers)
Date: 2025
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