Dynamic harmonic field analysis of an inverter-fed induction motor for estimating harmonic secondary current and electromagnetic force

The distorted power waveform from an inverter includes many time harmonic components which became a factor in increasing losses and generating noise. To evaluate the effect of these harmonic components quantitatively, this paper proposes a new harmonic field analysis method that considers the rotor movement dynamically and the harmonic components of the secondary current as induced current by a 2-dimensional finite element method (2D-FEM) using a time stepping technique. The proposed method is applied to the analysis of a cage induction motor supplied by a PWM inverter. As a result, the harmonic components of the secondary current and the electromagnetic force are shown quantitatively. These calculated results are confirmed by experiments measuring the secondary current and the sound level. From the comparison of calculated and experimental results, the proposed method is shown to be appropriate and useful for quantitative estimation of harmonic fields for inverter-fed induction motors.