Realisation of tests to determine the parameters of the thermal model of an induction machine

Tests are described to determine the parameters and coeficients of a thermal model, which allows one to estimate the stator and rotor temperatures in a three-phase induction machine, during operation. The model is obtained by analysing the power losses and the heat transmission inside the motor (considering it in two parts: stator and rotor) and with the environment. Two differential equations are deduced, which reflect, at each instant, the balance among the power losses, the evacuated heat and the stored heat in the motor. The study is carried out for a three-phase motor with a short-circuited rotor in a squirrel cage with nominal values: 1 kW, 380 V and 50 hz. From the stator and rotor temperatures provided by the thermal model, the updated values of the electrical resistances of the machine are obtained in real time during its operation.