Thermal Model of Totally Enclosed Water-Cooled Permanent-Magnet Synchronous Machines for Electric Vehicle Application

Totally enclosed water-cooled permanent magnet machines have been widely applied in electric vehicles due to their advantages of high torque density, high power factor, and strong overloading capacity. However, this type of machine often suffers from extremely high ambient temperature in a very limited space, which may lead to serious faults during operation, such as demagnetization. In order to study the thermal performance in depth, after investigation on the air convection within end-space, this paper presents a thermal model which takes into account the influence of the air temperature within the end-space on the temperature distribution by convection. Combining electromagnetic finite-element analysis with thermal resistance network, the thermal model is established, which is based on the law of heat flux balance in two continuous iterative calculations. Furthermore, computational fluid dynamic technology and experiments are implemented to further validate the proposed thermal model.