Abstract
A simple linear firing circuit using IC chips for an AC voltage controller working under variable-frequency anode supply is described. Its performance for an inductive load supports the theoretical conclusions. Features of the proposed scheme include symmetrical firing for both halves of the supply voltage, adjustable pulse width to the thyristor gates and linear variation in the firing angle with the control voltage which is independent of the anode-supply frequency over a wide dynamic range 1-120 Hz. The scheme may easily be extended to three-phase circuits