Experimental validation in operative conditions of winding thermal model for short-time transient

This paper presents the validation of a first-order winding thermal model in machine operative conditions. The proposed model can be used in motor control strategies for the winding temperature prediction during transient overload or vice versa, for the prediction of the maximum time duration of the overload maintaining the winding temperature within the limit imposed by the class of insulation. The thermal model has been validated using two different electrical machines. The first one is a 10 kW automotive starter-generator prototype for mini-hybrid powertrain equipped with distributed bar windings, while the second one is a 2.2 kW total enclosed fan cooled industrial induction motor equipped with conventional stranded wire windings. To both machines it is mainly required a short-duty transient operation in overload conditions. In particular, the automotive starter-generator must accomplish the engine cranking and torque assistance during the vehicle acceleration and braking, while the considered industrial induction machine has to operate in intermittent service in overload conditions for machine tool applications. As a consequence, an accurate stator winding temperature prediction is mandatory to fully exploit the machine performance. For both motors, the thermal model parameters have been evaluated by fast experimental approach and subsequently, the model has been validated during operative overload conditions.