Rotor Temperature Estimation for Saliency-based Control of Induction Motors using Symmetrical Transient Reluctance

Performance of flux-oriented control of induction motors is highly impacted by accurate knowledge of rotor temperature. Rotor temperature mismatches lead to deviations of flux and torque calculated by motor models, also modifying the actual magnetic saturation level. Saturation level, at the same time, strongly influences the parameters of machine saliencies used for speed sensorless control. This paper proposes a novel rotor temperature estimation method that is integrated in a sensorless control scheme, using a voltage step excitation method and extracting rotor slotting information as control signal. The same excitation method is also used to calculate the symmetrical value of the transient reluctance using a new parallel signal processing scheme. The amplitude of the symmetrical transient reluctance presents a temperature-dependent behaviour, which is exploited by a controller leading to accurate rotor temperature estimation. Proposed temperature estimation requires almost no additional resources. Experimental results are presented to verify excellent sensorless FOC performance combined with accurate rotor temperature estimation.