A Novel Cooling Technique for the Windings of High-Torque-Density Permanent Magnet Machines

In this paper, a novel cooling technique for the windings of high-torque-density permanent magnet machines is presented, that is, a miniature heat pipe inserting into the slot is adopted, thus, transferring the heat of the winding to the ambient air axially and increasing the convective area by fins. To describe the thermal performance accurately, a heat pipe with outer diameter of 2mm is tested and its thermal model is obtained according to the test result. To investigate the validity of the proposed technique, a lumped parameter transient thermal network (TN) model of the stator with heat pipes is established. The thermal performance of a 167W machine whose torque density is 5N·m/kg with this cooling technique is studied by using the thermal network. The analytical results show that the winding temperature is not more than 100°C when the current density is up to 12.5A/mm ² with 4m/s forced air cooling. A finite element analysis (FEA) model is built and simulated to verify the analytical results.