Design, Simulation and Comparative Analysis of Control Topologies for Thyristor Power Controllers

Every batch of reduction process for zirconium sponge production consumes nearly 4 MWh of energy in the operation of heaters. The heating circuit of reduction furnaces generally divided into four zones, each consists of nichrome heating elements fed by 3 phase, 415 Volts, 50 Hz AC supply. The process temperature is maintained by switching the state of these heating elements at specific intervals incorporating ON/OFF controller, using power contactors of suitable rating. However, in view of certain drawbacks of ON/OFF control system, thyristor power controllers have been proposed based on either phase angle control technique or integral cycle control topology. The paper presents the design schematic of these two control topologies and subsequently performs the circuit simulation to evaluate the parametric performance. The simulation results are also highlighted in the paper. The comparative analysis of phase angle control topology with integral cycle control scheme has been presented to find out the best temperature control strategy to keep the retort temperature within certain optimal limits. The FFT analysis of electrical parameters including total harmonic distortion, power factor and input waveforms has been discussed to meet the limits of IEEE: 519–1992. The paper also proposes a best suited control topology through comparative study to minimize the power consumption and maintenance downtime of reduction process enhancing the overall efficiency of the power system.