Rotor Temperature Modeling of an Induction Motor using Subspace Identification*

Knowledge of the rotor temperature is important for an efficient and secure operation of induction motors, especially in electric vehicles. However, in vehicle applications, measuring the rotor temperature is not possible, making a model-based estimation necessary. In this paper, the modeling of the rotor temperature is presented based on subspace identification, a black-box system identification method. The performed steps to achieve a high quality model are described in detail, including a systematic selection of inputs from the large amount of available signals. The resulting model is applied as an open-loop observer and evaluated using measurements of a specially equipped induction motor on a test bench, where the rotor temperature was measurable. Finally, some remarks are given regarding the on-board implementation of the identified model into a vehicle control unit for open-loop observation of the rotor temperature.