Effect of Loading of VSI-Fed Three-Phase Induction Motor on the Line Current THD
Kamal A. Khandakji |Pages: 53-60|

Abstract— Three-phase inverters using PWM are widely used in industry for speed control of three-phase motors. However, these inverters may significantly reduce the quality of the ac supply to which these inverters are connected; such inverters draw non-sinusoidal current from the mains. This leads to the generation of high-order harmonic current content. Usually, these harmonics are reduced by using passive filters like dc chokes or line chokes or/and active filters, which should be carefully chosen. In this work, the effect of loading of VSI-fed three- phase induction motor on the line current total harmonic distortion (THD) is experimentally tested and analyzed; line current THD vs. line current fundamental harmonic curves for different inverters are developed. Recommendations about the use of filters with adjustable parameters for effective harmonics mitigation with mechanical load variations are given. The use of the recommended filters can significantly decrease the line current THD independent of the actual load on the driven motor, enhance the quality of the power system and increase the energy efficiency.