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Power supply for an electric resistance melting furnace Alimadadi, Mehdi

Abstract

In recent years, the field of power electronics has experienced a large growth due to the confluence of several factors. Revolutionary advances in microelectronics methods have led to the development of controllers that include linear ICs and DSPs. Moreover, advances in semiconductor fabrication technology have made it possible to significantly improve the voltage/current handling capabilities and the switching speeds of power switches. This work is intended as a pilot 400kW unit for testing in the Advanced Material and Process Engineering Laboratory (AMPEL) building. The eventual goal of this project is to produce a full size commercial unit at 2.4MW. The conventional supply for an electric resistance-melting furnace consists of a singlephase low voltage source obtained from a 60Hz transformer. This high power single-phase load is becoming increasingly unacceptable to customers and a method of transforming the load into an effective balanced three-phase equivalent is sought. In single-phase sinusoidal loads the instantaneous power pulsates at twice the source frequency but the total instantaneous power drawn by a balanced three-phase load is constant. This implies that a substantial energy requirement must be present in any converter between the two systems or an unbalanced load to the three-phase source will be presented. Among the possible solutions, an AC/DC/AC conversion was chosen. A thyristor bridge rectifier is used as the AC/DC converter and a voltage source inverter is used as the DC/AC converter. Several previous papers have been reviewed to have a better idea on designing the DCbus filter, the effect of non-sinusoidal voltage/current on the transformers, etc. Practical considerations were one the most important factors in the design and choosing of the elements.

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