A Time-Domain Analysis of the Power Factor for a Rectifier Filter System with Over- and Subcritical Inductance

Abstract

A simple switching network in form of a rectifier filter is analyzed with application of time-domain methods. Exact expressions are derived for currents in the filter network and the ac supply line as functions of the size of a series inductor in the L-type low pass filter connected to a resistive load. The power factor as viewed from the ac supply line is derived from the time-domain expressions for conditions of continuous and discontinuous current. A current form factor is introduced in form of the ratio irms/iav to provide a measure for the added burdens that are imposed on the circuit components due to current deformations inside the switching network. Normalized numerical results for average and rms currents, their form factor, output voltage, and power factor are presented as functions of the ratio of the series inductance L and the critical inductance Lc in form of graphs. The presented treatment of the problem provides insights and information which would require cumbersome work if approached with the conventional methods of frequency domain analysis. Rectifier-filer systems with series inductances L<Lc, the critical inductance for which the inductor current i=0 at times, have recently gained significance for systems that provide energy to voltage or current regulators.