Self-circulation cooling structure design of permanent magnet machines for electric vehicle

The enclosed permanent magnet synchronous machines have been developed rapidly in recent years. The cooling of the rotor is a great obstacle in motor design because of the single way of heat dissipation. The wafters can only increase the air flow in end-space, the cooling performance for rotor is not satisfied. In this paper, a self-ventilated cooling structure is proposed. A novel inclined flow deflector is designed in this structure, which can promote the cooling efficiency of rotor. When the rotor rotates, the air pressure difference will be produced on both sides of the rotor axis, which makes the air circulate through the vent holes. To satisfy the cooling effect under various operating conditions, the highest permanent magnetic temperature-rise and air resistance loss are studied by Taguchi method, and the optimization scheme of the novel flow deflectors is determined, at the operating condition of rated, maximum torque, and maximum speed respectively. In the rated operating condition, the optimization scheme is compared with the motor adopted wafters, the permanent magnets temperature is decreased by 7%, the air resistance loss is decreased by 52%.