Study on the Fluid Field of Oil-Cooling PMSM Considering Oil Enters the Air Gap

In the oil-cooling PMSM, the oil that drips on the windings and motor cavity has a risk of entering the air gap when the motor rotates at a high speed. Since the oil viscosity is higher than the air viscosity, the mechanical friction loss increases when oil enters the air gap, resulting in a sharp rise in the rotor temperature. Therefore, based on experiments and simulation, the paths that oil enters air gap are analyzed in this study. And the CFD model of the oil-cooling motor is built to analyze the fluid field at various times. Friction loss and temperature are calculated at various speeds and oil volume ratios. The result shows that the process of oil entering the air gap changes the fluid form and increases the friction loss.