Determination of the magnetic losses in induction motors based on the generalized Epstein test

The results obtained from the standard method for the characterization of magnetic materials - the Epstein test - lead to significant errors in the estimation of magnetic losses in induction motors. Among the induction motor characteristics not accounted for in the Epstein test method, one can point out: winding distribution, cutting stresses, anisotropy, PWM supply and rotor losses (surface losses and interbar current losses). The generalized Epstein test method - GET - is introduced as an alternative to improve the estimation of magnetic losses in induction motors from tests performed on core material samples similar to the ones used in the standard Epstein test. In this paper, the GET is discussed and applied in the estimation of the magnetic losses in induction motors build from different core materials. Associated methods employed in the determination of the proper excitation harmonics and computation of rotor magnetic losses are also discussed. Experimental results are included to illustrate the proposed method.