Method for estimating the lifetime of electric motors insulation

In this paper we present the results of a study over the aging and the estimating lifetime of a new insulation system for a DC motor. In order to achieve the lifetime experiments, a group of 7 motorettes (made under IEC 60216-1) have been subjected to accelerated thermal aging at T = 260 ° C (for 1000 hours), followed by their requests to vibrations (1 hour) and humidity (48 hours). At every 200 hours were measured the insulation resistance, the losses factor and the electric capacity of motorettes, then these were tested in the AC withstand test voltage (600 V). The activation energy of oxidation of the enamel used as insulator of the conductors has been determinated by Differential Scanning Calorimetry (DSC). Considering as a diagnostic factor the insulation resistance and using the activation energy value determined by DSC the lifetime line to constant stress and then, the lifetime values for different temperatures were determined.