Design and Research of Permanent Magnet Brushless DC Direct Drive Hub Motor

The permanent magnet brushless DC motor has many advantages such as simple structure, high power density, small volume, good mechanical properties and high efficiency, so it is very suitable for electric vehicle. However, the traditional brushless DC motor has the disadvantages of flux weakening speed regulating difficulty and torque ripple. According to the characteristic of permanent magnet motor, so a kind of special structure brushless DC hub motor with outer rotor was designed in this paper. The structure of interlaced arrangement of permanent magnet and non-salient pole of the outer rotor greatly increased the average inductance of the stator winding, so as the range of flux weakening speed regulating increased greatly as well. At the same time, large chute in stator core and fractional stator winding reduced torque ripple of the motor. The simulation model was established by using Ansys Maxwell software and the magnetic field was calculated and analyzed. It turned out that the magnetic field was rational and the optimum designed motor had less flux leakage. Simulation and test results showed that stator performance indicators of the prototype could meet the requirements of electric vehicle fully. So it has great value of generalization in practical application.