Design and analysis of a water-cooling system in a new YASA in-wheel motor for electric vehicles

An in-wheel motor, as a key part of an in-wheel driving system, needs to satisfy strict restriction on thermal balance for increasingly high-power density in limited space and weight. Therefore, a new in-wheel motor with an innovative water-cooling system for one newly developed electric vehicle was developed. Based on mechanical structure of the motor, all potential water-cooling layouts were firstly designed with consideration of mechanical strength and manufacturability. A thermal conjugate simulation model of the developed in-wheel motor was then built and its thermally fluid-solid interactions were investigated in this study. All potential water-path layouts of the motor were compared regarding cooling effect and fluid resistance, which impact performance of the motor. Fluid flow velocity and fluid state, determined by the water-path layout, significantly impact cooling effect of the motor. The well-designed water-cooling system significantly reduces motor's temperature at a low cost on required coolant driven pressure which benefits the efficiency of the developed motor. A prototype of the developed motor with the optimal water-path layout was built and tested on the test rig. The developed motor provides outstanding thermal performance.