Dual Controller for Inductive Loads

Abstract

A controller for inductive loads is introduced and analyzed. The controller operates as follows: a capacitor begins to charge through an inductance at an angle α of the positive half-cycle of the supply voltage. At the same time a second capacitor previously charged in the negative half-cycle begins to discharge in the load. A dual action takes place in the negative half-cycle. Power control is achieved by means of changing the firing angle α. The controller circuit description, theory of operation, analysis, and numerical results are given along with experimental results. It is shown that the controller gives a very high input power factor, over a wide power range, much higher than the load power factor to sinusoidal currents. Thus for a load whose cos ϕ = 0.2, an input power factor greater than 0.9 is achieved over a power range 10-100 percent. Also the controller gives rise to negligible distortion in the supply and load current waveforms. © 1979 IEEE