Cooling Performance and Loss Evaluation for Water- and Oil-Cooled without Pump for Oil

This paper describes the cooling performance and fluid friction loss of water- and oil-cooled system for a motor in which parts of the rotor are soaked in oil coolant. To miniaturize the motor, the proposed cooling system does not use a pump or cooler. We developed a test motor and measured the proposed cooling system's fluid friction loss and temperature reduction effect. As a result, (1) the water- and oil-cooled can reduce coil temperature by 24% com pared with the water-cooled system; (2) the calculation error of the fluid friction loss of the rotor parts soaked in oil coolant is 30% at maximum; and (3) the water- and oil-cooled system has almost the same loss as the water-cooled system which demonstrating higher cooling performance.