Assessment of available methods for estimating rotor temperatures of induction motor

Rotor bars of induction motors are at a high risk of thermal damage during heavy overload, impaired cooling conditions or prolonged starting. State-of-the-art relays for induction motors utilize a starting inhibit algorithm for the thermal protection. In many cases, it is too conservative and can not adapt to the changes in the motor´s cooling capability. This paper reviews available thermal model-based approaches and parameter-based approaches to estimate the rotor bar temperature for line-connected induction motors. Under the condition that only voltage sensors and current sensors are used, these methods are discussed, implemented and compared based on experimental results. This paper provides guidelines on rotor temperature estimation for line-connected induction motors.