Power factor correction and harmonic mitigation in a thyristor controlled glass melter

Severe disturbances to other plant functions resulting from operation of a new all-electric glass melting furnace in a manufacturing plant are discussed. The problem was traced to the thyristor controllers which regulated power to melter electrodes. Investigation showed severe distortion of the plant feeder-voltage waveform due to harmonic currents. Corrective measures consisted of installing a set of series-resonant harmonic traps and a high-pass filter on the 460 V feeder. Harmonic distortion of supply voltage was reduced from 5% to less than 1%, and power factor was improved.<>