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

A thyristor-based power circuit was recently implemented for the temperature control of the tin bath in a float glass manufacturing process. Heat control is accomplished by individual thyristor-based devices utilizing zero-voltage-fired thyristors in time proportioning mode for transformer primary voltage modulation. This approach allows fewer transformer taps while causing no degradation of circuit power factor. In addition, harmonic distortion usually associated with phase-angle control in this application is eliminated. The authors provide an update on this temperature control system, including information relating to system performance, harmonic distortion, and power factory history after about one year of operation.<>