Development of 13-V, 5000-ADC Power Supply with High-Frequency Transformer Coupling Applied to Electric Furnace

This paper describes a low-voltage and large-current DC power supply with a high-frequency transformer coupling, which is applied to electric furnaces. The power supply is simply composed of a full-bridge inverter, an amorphous-core step down transformer and a Schottky diode rectifier. The magnetizing frequency of the transformer is raised up to 15 kHz and the maximum output rating of this system is 13 V and 5000 A. The most important key feature of this system is reduction of line inductance and leakage inductance in the whole power circuit, which exist mainly in wire harnesses, the transformer windings, the output DC bus, etc. Even such inductance of micro-Henry order detrimentally affects the total output power to the load because a long overlapping period in commutation of the final rectifying stage can be caused by the large current and such minute inductance. The maximum total efficiency between the utility AC power source and the load is 89.9% and the maximum total input power factor at the front end stage of the prototype is 83.5%, respectively. Although the output voltage and the current of the system are considerably low and large, the confirmed experimental results demonstrate rather excellent performance and feasibility of the developed system, compared with conventional thyristor-based power supplies.