Effect of Cooling Methods on Continuous Output Capability of a Permanent Magnet Synchronous Motor

Operating points of a vehicle traction motor widely spreads in speed-torque (N-T) plane from low-speed high-torque to high-speed low-torque region. So, expanding continuously operatable region over N-T plane is important. Cooling methods selection is crucial for the purpose, but it has not been reported very well how cooling methods affect to the region expansion. In this paper, effect of cooling methods on continuous output capability improvement is studied. As cooling methods, a Case Water Jacket (CWJ), End-Winding Filling (EWF), a Rotor Shaft Oil Supply (RSOS) and a Rotor End Oil Impingement (REOI) cooling are selected from the point of ease of application. As first step, motor components temperature with only the CWJ cooling is calculated by using a Lumped Parameter Thermal Network (LPTN). So, relation between critical temperature portions and continuous output capability is clarified. As next step, continuous output properties under combination with the other cooling methods are calculated and compared. So, the effect of the cooling methods selection on continuous output capability improvement is clarified.