AUTOMATIC VOLTAGE CONTROLLER

PURPOSE:To improve the voltage control accuracy by switching the taps of plural boosting transformers with tap switches in the prescribed order so as to select each tap at one time. CONSTITUTION:When a drop pulse DP is outputted from an anti-time limit timer 13, a flip-flop 24 switches a switch circuit 23 to connect a common connection terminal 23c of the circuit 23 to a switch connection terminal 23b. As a result, a drop pulse DPb is applied to a boosting transformer 2B with tap switch and the tap of this transformer 2B drops by a step. Then the output voltage of the transformer 2B drops by a step. Therefore the output voltage levels of the boosting transformers 2A and 2B with tap switches are controlled so that the output voltage applied to a system 3 is coincident with the set value VR of the system voltage. Then the fluctuation of the system voltage is reduced and the voltage control accuracy is improved.