Quasi continuous control of sinusoidal AC voltage - uses full wave rectifier and control voltage derived from it through RC filter element

摘要

The sinusoidal voltage is keyed by an a.c. switch with two antiparallel thyristors. The keying ratio is controlled by the full wave rectified a.c. voltage to be controlled, through an RC filter circuit determining the keying ratio and frequency. The thyristors in the switch are controlled by a control quantity obtained by comparison of the filter circuit voltage with the mean keyed sinusoidal voltage. It is done through a synchronisation device (with a control logic system) by a pulse generator at zero crossings of the sinusoidal voltage. Filter voltage (U M) is produced as actual value (U'ist) of the quasi continuous voltage control by key modulation of the full-wave rectified a.c. voltage (u'v) to be controlled. Its variable keying ratio (m) is proportional to the instantaneous value of this a.c. voltage, and the key modulated rectified a.c. voltage (U M) is integrated.