this paper proposed a new yokeless and segmented armature axial flux machine (YASA) applied in-wheel traction. The loss analysis for the motor is performed based on finite-element method (FEM), and several methods are adopted to increase the efficiency and the output power of the motor. Subsequently, a novel cooling system is proposed, and the thermal analysis of which is conducted. On this basis, computational fluid dynamics (CFD) is developed to investigate and optimize the cooling system to increase the heat transfer efficiency. And finally, the in-wheel motor is manufactured and tested. It can be concluded that the measured data matches well with the results of the electromagnetic and CFD analysis, and the peak power of the motor has been increased from 50kW to 65kW before and after improvement.

In this paper, a novel cooling system of the yokeless and segmented armature axial flux machine (YASA) applied in‐wheel traction is presented. Although the cooling system has high cooling efficiency, it will deteriorate the electromagnetic characteristics of the motor. The eddy current analysis for the prototype is performed based on the 3‐D finite‐element method, and the distribution of eddy current in the cooling fins is presented. Through the 2‐D finite element analysis, the cause of the eddy current loss of the fin is revealed. In order to increase the output power of the motor, the height of the fin in the axial direction is optimised by the magneto‐thermal coupling method. And finally, the hub motor is manufactured and tested. It can be concluded that the measured data matched well with the analysis results.

An in-wheel motor, as a key part of an in-wheel driving system, needs to satisfy strict restrictions 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 the mechanical structure of the motor, all potential water-cooling layouts were first 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 the cooling effect and fluid resistance, which impact the performance of the motor. Fluid flow velocity and fluid state, determined by the water-path layout, significantly impact the cooling effect of the motor. The well-designed water-cooling system significantly reduces the 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.

This paper takes the demand of high power density motor for new energy vehicles as the application background. In order to solve the problem of low power density of radial flux motor, a novel direct cooling yokeless and segmented armature axial flux machine (YASA) is proposed. The thermal-fluid multi-physical coupling field of YASA motor has been studied by combining numerical analysis and computational fluid dynamics (CFD). On this basis, the internal relationship among the output power, flow resistance and structural parameters of the cooling system has been studied, and then the parameters of cooling system has been multi-objectives optimized. On the premise of meeting the pressure loss of the cooling system, the heat transfer efficiency has been improved, and then the output power of the motor has been increased.

This paper mainly analyzes the influence of heat of the brake disc on the permanent magnet of yokeless and segmented armature axial flux machine (YASA) applied in-wheel traction when the vehicle is braking. Firstly, the influence of braking system on hub motor during emergency braking and long downhill braking is analyzed by computational fluid dynamics (CFD). Subsequently, a novel heat exchange system is proposed, and the thermal analysis of magnet of the hub motor with and without heat exchange is conducted. And finally, the hub motor is manufactured and tested. It can be concluded that the measured data matches well with the results of the CFD analysis, and the max temperature of the magnet of the hub motor decrease from 158 ℃ to 123℃ during long downhill working condition with the proposed heat exchange.