Thermal Characterization of a Power Loss Minimization Technique in Induction Motor Drives

This paper is focused on the experimental identification of the variability of the minimum point of power losses as a function of the thermal state condition of an induction motor drive. More in detail, once identified the optimal level of magnetization of a 5.5 kW three-phase induction machine for the minimum absorption of power losses for different conditions of operation in terms of load and speed, the variability of these values has been characterized as a function of the induction motor frame temperature. The experimental results highlight the need to account for the machine's thermal state when optimizing the performance, due to a shift of the power curves. Therefore, the control algorithm for loss minimization must recognize this thermal variation to properly adjust the value of the loss variable and optimize the power efficiency of the whole system.