Development and analysis of an input power factor corrected variable speed motor drive system

This paper provides the improvement of the system power quality which involves a high power factor (PF) and low total harmonic distortion (THD) by employing an active input power factor correction (IPFC) circuit as a front-end converter for the variable speed induction motor drive system. The variable speed motor drive (VSMD) saves more electrical energy than the fixed motor drive under the assumption that both are operating on the same load factor. Almost all of the small VSMDs have no IPFC circuits to save their production costs. A three-phase inverter-fed induction motor drive (IMD) with a single-phase source and an active IPFC circuit is proposed in this paper to study the impact of IPFC circuit experimentally. The foremost subject in the study of an input PF corrected VSMD are the effects of an IPFC circuit on overall system efficiency and input PF. Empirical comparisons between the conventional bridge rectifier circuit and IPFC circuit in terms of PF and efficiency against motor speed are developed. A steady-state model of the IMD, including a three-phase inverter and an active IPFC circuit, is developed to predict system performance. The analytical results are correlated to the experimental results obtained from a prototype one-horsepower IMD with a constant volts per hertz (V/Hz) control strategy. The overall system performance with an IPFC circuit is better than the system performance without it in terms of harmonic contents and PF. The system efficiency, however, shows marginal inferiority with an IPFC circuit because the front-end IPFC circuit and the three-phase inverter are connected serially. It should be emphasized that the IMD with IPFC is desirable in utilizing the generated electrical energy effectively and minimizing the harmonic contamination.