In this paper, the cooling performance of oil-cooling PMSM with hairpin winding under various oil parameters is analyzed via a simulation and an experiment. The effects of oil jet positions, oil temperatures, and oil flow rates on the cooling performance are analyzed. It is found that increasing the oil temperature in the range of 20 °C to 60 °C, increasing the flow rate of oil jets whose position angle is from 15° to 45°, and increasing the flow rate in the range of 1 L/min to 2 L/min will significantly improve the cooling performance. The apertures of the oil spray ring are optimized using the Taguchi algorithm. The cooling performance is the best when the flow ratio is m(0°):m(15°):m(30°):m(45°):m(60°):m(75°) = 4%:19%:10%:10%:4%:4%. This study provides a guide for the design of the oil-cooling system for the hairpin winding of the PMSM.

Studies on the central and bilateral bridges of interior permanent magnet (IPM) motors often focus on individual mechanical strength or electromagnetic performance, lacking comparative studies on the electromagnetic performance of motors with different central and bilateral bridges under the same mechanical strength. This paper designs three rotors with different central and bilateral bridges and compares the electromagnetic performance of the three motors. First, to ensure the safe operation of the three rotors at high speeds, the mechanical stress of each rotor has been analyzed using the finite-element method (FEM). Subsequently, the major electromagnetic performances of the three motors are analyzed and compared, including the air-gap flux density, back electromotive force (back-EMF), inductance, salience, torque, power, loss, efficiency, and demagnetization. The results indicate that the rotor without central bridges has the largest leakage flux and the lowest torque but exhibits minimal torque ripple. The rotor with narrower bilateral bridges has the highest torque and maximum torque ripple. The torque performance of the rotor with wider bilateral bridges lies between the two aforementioned motors, and it possesses the highest efficiency. In the end, by adjusting the dimensions of the permanent magnets, the torque of all three models increases, but the motor with narrower bilateral bridges still has the largest torque. These findings provide valuable references for rotor design.

To improve the power density of permanent magnet synchronous motors (PMSM) for electric vehicles, round wire winding is gradually replaced by flat wire winding. The large cross-sectional area of the flat wire winding causes significant AC loss and temperature. AC loss includes the eddy current loss and DC loss. The eddy current loss in the high-frequency region needs to be suppressed, and the slot fill rate needs to be guaranteed to suppress the DC loss in the high-torque region. The loss distribution of different layer windings is affected by the distribution of magnetic leakage in the slot. The magnetic leakage is generated by the joint action of armature current and the permanent magnet. Based on the analysis of the causes of AC loss in different layers under various working conditions, this paper proposed the layered loss suppression method (LLSM). The novel hybrid-cross-section flat wire winding (HCSW) is proposed based on the LLSM and verified by experiments. Results show that the loss of HCSW is reduced by 21.4% in peak speed working condition and the slot fill rate is guaranteed. The area of the high efficiency region is increased by 11% compared with the original model.