A Single-Phase Controlled Rectifier with Unity Power Factor

An approach recently introduced to correct the power factor of single-phase and three-phase diode rectifiers is extended to single-phase line-frequency phase-controlled rectifiers. First of all, the conventional circuit of the thyristor based rectifier is proposed to be modified in order to make possible the control of the DC-voltage mean value also in presence of a fully resistive behaviour of the DC-load, being this last an imperative constraint for the proposed power factor correction technique. Then, the power factor of the new controlled single-phase rectifier is corrected by using a simple, reliable and economical passive correction technique, simply based on the use of a resistive-capacitive branch to be connected at the DCterminals of the rectifier. The designing procedure of the introduced passive correcting branch is investigated. Analyses of performances of the new controlled rectifier are developed with the help of several PSPICE simulations on a case-study of about 2.5 kW of active power and under different working conditions. Some perspectives on the possibility to improve the conversion efficiency of the introduced rectifier, sensibly worsen by the introduction of the dissipative correcting branch, are also developed. Key-Words: Controlled rectifier, DC Motor Drives, Power Factor Correction, Total Harmonic Distortion Factor, Conversion Efficiency.