Observation of transients in the series-connected saturable reactor with high-impedance control source

In a series-connected saturable reactor working in the proportional mode with its control winding fed by a direct current from a high impedance source, the gate current as a function of time has a rectangular shape and its amplitude, in ampere turns, is equal to the magnitude of the control current.1 Full-wave rectification of the gate current yields a direct current closely proportional to the control current, regardless of changes in line voltage, frequency, and load resistance. Hence the name d-c transformer. This relation holds in general even under transient conditions. For instance, the gate current follows changes in the control current instantaneously and a ripple component in the control current is reproduced faithfully in the gate current even when its frequency is higher than that of the power source.2