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Large furnace (furnace) Medium-frequency electric furnace As mentioned earlier, the high-voltage power supply operating at power frequency has a power density of 600 W/m². If a medium-frequency induction furnace weighing over 1 ton is equipped with a power supply rated at 1250 kW and uses a 380 V power supply at power frequency, the resulting DC output voltage would be...
380 × 1.35 = 513 V
Intermediate-frequency voltage
513 × 1.4 = 718 V
Direct current
1250 ÷ 513 = 2437A
Suppose the Q value of the resonant load circuit, composed of an electrothermal capacitor and a furnace body, is 10. In the flat-pressure configuration, the current in the resonant circuit is:
9.20
2437 × 10 = 24370A
As can be seen, the large current leads to higher manufacturing and installation costs, resulting in reactive power losses due to Joule heating. If a 50-Hz power supply is used at 850 V, the DC output voltage would be 850 × 1.35 = 1147.5 V.
Intermediate-frequency voltage
1147.5 × 1.4 = 1606.5 V
Direct current
1250 ÷ 1147.5 = 1089 A
The Q value of the resonant load circuit composed of the electrothermal capacitor and the furnace body is 10. In the flat-pressure configuration, the current in the resonant circuit is:
1089 × 10 = 10890A
It is evident that the current flowing through the water-cooled cable and the induction coil has been reduced by a factor of 0.45. Therefore, using high-voltage AC power supplies—such as 50 V, 660 V, 750 V, 90 V, and 1250 V—with a specific voltage rating of over 2 tons—is an excellent approach for energy conservation and consumption reduction. On the one hand, this is made possible by the superior performance of modern electronic switching devices; on the other hand, it also calls for power supply bureaus serving industrial enterprises to collaborate closely with these enterprises under the overarching principle of energy saving and emission reduction, thereby ensuring reliable and efficient power supply.