Design of Novel Spiral Magnetic Poles and Axial-Cooling Structure of Outer-Rotor PM Torque Motor

This paper introduces a Permanent Magnet (PM) synchronous torque motor with an external rotor. Firstly, the basic structural features of this motor are described. Novel spiral magnetic poles and axial-cooling structure is designed to increase the energy density and make the motor compact. The width, thickness and spiral angle of the poles are determined by magnetic computing, in order to ensure the wave of gap magnetic density is sine. To provide an effect cooling structure, the motor side hoods are designed as centrifugal fans to cool the coil down. Multiple air channels are cut in the stator core to increase the ventilation of air. The spiral poles can also constitute spiral air channels and produces wind to cool the magnets. It is possible to choose high electromagnetic load to gain high energy density based on a good cooling effect. Next, the method is determined and the program is compiled for electromagnetic computing. The finite element analysis on magnetic field is conducted by applying ANSYS. Finally, according to the optimization of the structure, a 3 kW prototype is fabricated. The no-load and load experiments are carried out to proof the performance of the motor.