Sensorless Rotor and Stator Temperature Estimation in Induction Motor Drives

Temperature monitoring is a major issue in induction motor drives, because temperature variations with the working conditions may affect the machine lifetime and the control performance as well. The paper presents a technique for on-line monitoring the rotor and stator temperature on field oriented induction motor drives, based on a new approach to estimate the rotor time constant and stator winding resistance. The proposed approach exploits the injection of small additional current signals to extract the thermal status of the electrical machine, without affecting the normal drive operation. Moreover, it does not require other transducers than those normally already present in a standard field oriented controlled drive and can be applied on both conventional and sensorless induction motor drives. The stator and rotor temperature estimation can be used either to prevent dangerous overheating, either to on-line tuning the control system. The practical effectiveness of the proposed approach is demonstrated by simulations.