An unity PF controlled rectifier driving a shunt DC motor for power quality application

This paper describes a technique to achieve low harmonics and unity power factor for a three-phase controlled rectifier based dc motor drive by applying a simple current injection topology. This scheme consists of a thyristor bridge, three bi-directional current by-pass switches, and a simple current shaping network. The bi-directional switches are switched at double the line frequency while its current shaping network consists of only two capacitor and three resistors. Input current THD and power factor of the controlled rectifier is within acceptable limit even some variation in bridge working conditions, due to changes in either load or bridge delay angle are happened. The scheme provides a simple, light, fast, and economical upgrading to controlled rectifier based DC drives. The effectiveness of this method has been confirmed by both simulation and laboratory tests.