A Thyristor Alternating-Voltage Regulator

The control of thyristors used in alternating-voltage regulators employing synchronous tap changing is normally complicated when there are wide variations in load power factor. The modified form of tap changing circuit described here simplifies these control problems and because of the different operating mode produces less distortion in the output waveform. The essential feature of this circuit is that a tapped inductor carrying a controlled direct current is connected in the output circuit of the regulator. This inductor prevents tap-to-tap short circuits and effectively provides an additional output voltage level.