Grid-controlled phase-advancers

Abstract

By connecting a charged capacitor between the anode and the cathode of a grid-controlled valve it is possible to break off the current through the valve. The paper deals with circuits for grid-controlled phase-advancers based on this principle. Into the circuit of a conventional grid-controlled rectifier are introduced auxiliary valves and a capacitor. The capacitor is connected, through the auxiliary valves, in parallel with each of the principal valves in turn, and extinguishes them. The effect of this is to make the current lead the voltage. There are (a) double-step circuits with two groups of valves and a capacitor which extinguishes in turn the valves of the first and of the second group; and (b) multistep circuits with N groups of valves and N capacitors changing their charge in a periodic fashion. The paper includes formulae and diagrams for the computation of the rated-output factors of the extinguishing capacitor and the smoothing reactor respectively. Experimental results and oscillograms are given which confirm theoretical conclusions. A grid-controlled phase-advancer can be utilized to improve the power factor of an a.c. main, instead of rotary machines or static capacitors.