Dynamic harmonic field analysis of an inverter-fed induction motor considering all harmonic components in the secondary current

This paper describes a quantitative method to analyze the harmonic fields of induction motors dynamically, considering all the higher harmonic components in the secondary current under the given analysis conditions. The method consists of two parts. Firstly, a magnetic field calculation is performed using a 2D-finite element method considering rotor movement, and then a harmonic analysis is carried out by considering the space and time harmonic components using results from the first part of the calculation. Dependence of periodicity on the magnetic fields, under the load conditions considering the rotor slip, is discussed. The relationships between the analysis period, the method of mesh division, and the periodicity are then clarified to facilitate calculation of the magnetic fields. The computation time needed to solve the magnetic field can be reduced by using these relationships. The method is applied to the analysis of a 240 kW cage induction motor supplied by a PWM inverter. From comparison of calculated and experimental results, the proposed method is shown to be appropriate and useful for the quantitative estimation of the harmonic fields in inverter-fed induction motors