In recent years, the power, torque, speed, and other performance of interior permanent magnet synchronous motor (IPMSM) for electric vehicles have improved. The temperature rise is an important factor limiting the performance of the motors. In this article, a novel hollow shaft oil injection cooling structure is proposed. The cooling oil is passed in from one end of the hollow shaft and enters the permanent magnet cavity through the radial oil channel. The centrifugal force generated by the rotation of the rotor causes the oil to be sprayed from the oil injection holes on the end caps at both ends of the rotor, and the winding ends and the stator are directly cooled, which reduces the internal temperature of the motor. The Taguchi method is used to analyze the influence of the novel hollow shaft oil injection cooling structure on the average temperature of the winding and the difference in the injection flow rate at both ends of the motor. Considering various operating conditions, the optimization scheme of the cooling structure is determined. Finally, the reliability of the structure is verified by stress calculation and modal analysis.

The Halbach array permanent magnet machine has several advantages. Most notably, it has more sinusoidal air-gap flux density distribution, higher air-gap flux density amplitude, and self-shielding magnetization property. In engineering, the segmented Halbach array is usually used considering the complexity of fabrication, and certain gap exists between segments inevitably. To analyze the effect of the gap between segments on air-gap flux density, an analytical model of the Halbach array permanent magnet machine considering the gap between segments is established in this paper. The finite element model is adopted to validate the established analytical model. Furthermore, effects of the parameters of the segmented Halbach array, including gap between segments, segment number per pole, and pole pair number on the fundamental amplitude, and waveform distortion factor of the radial component of air-gap flux density are analyzed using the established analytical model.

In this paper, a rotor magnetic potential (RMP) model is proposed, which can accurately describe the rotor surface magnetic potential distribution under the interaction of multi-excitation sources. Furthermore, a new magnetic equivalent circuit (MEC) model is used to model the complex saturation in the bridge region, which employs an improved nonlinear reluctance modeling method. Then, the unknown parameters in the RMP model are obtained by solving the MEC model. In this paper, the RMP model and MEC model are combined to consider the stator and rotor saturation effects, and the magnetic field is calculated accurately. Compared with the existing RMP model, the proposed one can take into account the effects of the stator saturation and PM magnetic field. Compared with the existing MEC and equivalent magnetic network (EMN), the area of the nonlinear reluctance in this paper varies with excitation conditions, which can accurately consider the saturation effects in the bridge region. This improvement can improve calculation accuracy on the basis of reducing the number of nonlinear reluctances. Moreover, the proposed method does not need to consider the change of the air-gap reluctances caused by rotor rotation. Finally, the proposed method is verified by both finite element analysis and experiments.

The iron loss of the interior permanent magnet (PM) machine is larger when the machine runs at a higher speed. The great stator and rotor iron loss have a negative effect on the machine, so the PM cavity of the interior PM machine with a single-layer U-shaped PM geometry is improved to reduce the iron loss of the machine in this paper. Meanwhile, the Taguchi method is utilized to optimize the improved PM cavity at the rated point, maximum torque point, and flux-weakening point, respectively. The effects of each optimization variable on the iron loss and electromagnetic torque of the machine are analyzed. Then, the optimization scheme of the improved PM cavity is achieved at each selected operating point, respectively. The final optimization scheme of the improved PM cavity will be concluded after the overall consideration of optimization schemes at the selected operating points. In addition, the electromagnetic torque ripple and cogging torque are also effectively reduced by adopting the improved PM cavity, which improves the running stability of the machine.