Unbalanced Voltage Control of 3-Phase Loads by the Triggering of Silicon Controlled Rectifiers

It is shown that smooth nonreversible control of the unbalanced voltages applied to a 3-phase load may be obtained by using one or two back-to-back SCR pairs. The magnitude of the fundamental components of the nonsinusoidal load voltages can be accurately calculated by Fourier series. Two connections are given which yield smooth reversible voltages, suitable for 3-phase motor control.