Piecewise variable parameter model for precise analysis of iron losses in induction motors

Abstract

This study proposes a two-term piecewise variable parameter model for precise prediction of iron losses in induction motors. In this model, two additional flux density terms reflect the non-linear magnetisation and the harmonic fields in the motors, and the main loss parameters are piecewisely variable with the magnitude and frequency of flux density, so that higher accuracy of iron loss prediction can be achieved for a large range of flux density frequencies and magnitudes. Meanwhile, the fine analysis of the fundamental and harmonic iron losses can also be carried out with the proposed model, and the influence of the harmonic fields on the hysteresis and eddy current losses can be revealed. Experimental validations are carried out on the laminated steels, DR510 and DW470, as well as, the Y132S-4, 5.5 kW and YX3-250M-4, 55 kW induction motors whose cores are made of the above steels. The experiments on the motors are performed with the voltage supply of different magnitudes, and both the proposed model and Bertotti model are used to predict the iron losses. It is shown that the iron losses predicted by the proposed model agree well with the test results over a wide range of supply voltages. This study contributes the technical support for the development of new premium efficiency motors.