Definition and Experimental Validation of a Second-Order Thermal Model for Electrical Machines

This article proposes a second-order thermal model useful to predict the average winding temperature of electrical machines used in electrical drives. Both analytical and practical considerations are provided. The proposed model is first described, including the physical meaning of each thermal parameter. Then, an experimental procedure to properly calibrate the thermal parameters of the proposed model is presented in detail. Later, experimental results providing the validation of the proposed thermal model both in transient and steady-state thermal conditions are presented, including their in-depth analysis. Although the proposed thermal model is calibrated and validated on a totally enclosed fan cooled induction motor, it has general validity, such that it can be adopted for any electrical machine, regardless of windings type, e.g., distributed or concentrated. The simplicity of the proposed thermal model and its high accuracy in estimating the average winding temperature make it useful in electric drives, e.g., its implementation on motor control algorithms to perform proper overload strategies.