Electromagnetic field analysis on high-power disc-type AC permanent magnet synchronous motor

A 3D electromagnetic field was modelled and simulated in the design of a 510 kW disk-type AC permanent magnet synchronous motor used on oil drilling platform. Considering the symmetry and periodicity of this model, the model was simplified into a one-fourth part hence the computing workload was greatly reduced. Under no-load condition, the no-load flux density distribution and the effects of pole arc-coefficient, slot opening width, and slot-pole combination on the cogging torque were analyzed. By optimization, the minimum value of cogging torque was 30.64 N·m when the pole arc-coefficient was set 0.85, the slot opening width was set 5 mm, and an 18 slot-16 pole combination was adopted. This significantly reduced motor torque fluctuation, hence reduced vibration and noise levels and improved the control accuracy and quality of the system. When the motor was working under loading condition, the waveforms of electromagnetic torque were analyzed under different exciting currents and inner power factor angles. The electromagnetic torques under different operation conditions were also obtained. Research shows that the electromagnetic torque density of this motor increases significantly compared with other motors with the same volume, and its adjustment margin of inner power factor angle is quite large, satisfying the requirement of overloading. Moreover, according to the obtained no-load and load parameters, the vectorgraph of this disk-type synchronous motor was drawn and the synchronous inductance value of 0.31 mH was obtained.