Cooling System Design of a High-Speed PMSM Based on a Coupled Fluidic–Thermal Model

To avoid overheating of a totally enclosed high-speed permanent magnet synchronous machine (PMSM) with an amorphous alloy core, this paper proposes a hybrid cooling system with both radial and axial vents to maintain the temperature rise below the rated value. The analytical models of cooling ability and frictional loss generated in the rotor ducts are derived in relation to the cooling structure parameters. The sensitivity of each parameter to the cooling effect is researched, and the parameter scopes are then determined. A coupled fluidic-thermal model based on the cell method is developed to predict numerically the temperature distribution to check the effectiveness of the cooling system. By analyzing the influences of the numbers and sizes of the cooling ducts on the efficient cooling air quantity and temperature, the feasible parameters that yield reasonable temperature distribution can be determined. The theoretical results are confirmed by experimental test results on a 15-kW 30 000-r/min PMSM prototype.