Induction motors thermal monitoring by means of rotor resistance identification

Rotor and stator temperature are of concern in both short-term machine protection and in longer term condition monitoring for large induction machines. Especially, when operating with overload cycles, it is necessary to monitor rotor bars and stator winding temperatures to make sure that the temperature remains below prescribed limits. The purpose of this paper is to present a thermal monitoring technique, for induction motors steady-state operation, based on the rotor resistance identification. Experimental results, for a 4-kW four-pole squirrel cage induction motor, show the industrial viability of the proposed technique.