Zero-voltage-fired transformer-coupled thyristor power control applied for temperature control of the tin bath in the float glass process

A novel thyristor-based power circuit is described that substitutes zero-voltage-fired time-proportioning control and thus allows fewer transformer taps while causing no degradation of circuit power factor. Harmonic distortion usually associated with phase angle control in this application is eliminated. A system description outlining power requirements, a comparison of power factor costs, and system design philosophy are provided along with some operational history and an explanation of the thyristor control