| Evaluating Hybrid Cooling in In-Wheel Motors with Reduction Gear for Electric Vehicles |
| Myeong Hyeon Park1, Ed Joshua Manalac2, Sung Chul Kim2 |
1LG Electronics, 51 Gasan digital 1-ro, Geumcheon-gu, Seoul, 08592, Korea
2School of Mechanical Engineering, Yeungnam University, Gyeongsan-si, 38541, Korea |
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Received: November 4, 2024; Revised: February 18, 2025 Accepted: March 6, 2025. Published online: April 27, 2025. |
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| ABSTRACT |
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The temperature of the windings of in-wheel motors affects the performance, efficiency, and driving distance of electric vehicles. During motor operation, heat is primarily generated in the coil. Additionally, the reduction gear integrated into the in-wheel motor assembly also generates much heat due to friction. Oil spray cooling (OSC) dissipates the heat better compared to other conventional methods; however, the components that are not directly sprayed exhibit elevated temperatures due to reduced cooling effect which results to temperature non-uniformity. Application of passive cooling combined with OSC can overcome these limitations. In this study, a hybrid cooling (HC) model that integrates rotational OSC and conduction cooling method using conductive silicone for an in-wheel motor with reduction gear is proposed. Silicone was applied to the outer surface of the end-windings, and the cooling performance of the HC method is evaluated. Due to the enhanced conductive cooling from the thermal conductive silicone, the temperatures of the in-wheel motor components are reduced by an average of 2.5 °C. Due to HC, the cooling performance of the coil and stator increased by 4.6% and 5.2%, respectively. Additionally, the temperature uniformity of the coil substantially improved. The heat flux at the surface was determined to be in the range of 1400–1900 W m-2. |
| Key Words:
Motor cooling · In-wheel motor · Reduction gear · Hybrid cooling · Oil spray cooling · Cooling performance |
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Corresponding Author.
Sung Chul Kim , Email. 
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