The a-c voltage control circuit, composed of parallel connection of a SCR and a reactor, gives the similar performance as the control circuit of a back to back SCR pair. However, the control characteristics of this circuit is affected by magnetizing characteristics of reactor. In this paper, the circuit with the resistive load has been analyzed by using the approximated models of hysteresis loop of core materials, where the SCR's forward voltage drop is taken into account. The results of the analysis have revealed the facts as follows, I) The control characteristics of the a-c voltage in average value is independent on the magnetizing characteristics of reactors except in the vicinity of minimum output point. But, in effective value, it is not valid. 2) A SCR's forward voltage drop results in the reduction of not only SCR's current but also reactor's current. 3) The a-c output current does not include the d-c component, if the winding resistance of the reactor is negligible.