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High-power molten iron preservation has traditionally been dominated by core-type power-frequency induction furnaces. The successful application of high-power coreless medium-frequency induction furnaces for high-power molten iron preservation represents a pioneering achievement in China. Currently, a 50-ton coreless medium-frequency furnace for molten iron preservation is already in operation. As a preservation furnace, the thyristor-based coreless medium-frequency induction furnace offers significant advantages over the core-type power-frequency induction furnace. Based on twenty years of practical application experience, the following conclusions have been drawn: Coreless medium-frequency induction... Electric furnace Performance Comparison with Core-Type Power Frequency Induction Furnaces (Taking Cast Iron as an Example)

Intermittent smelting operation Medium-frequency furnace Each time, the slag can be completely cleared, and when starting a cold furnace, there’s no need to lift the melting charge. This also limits the overheating time of the charge size and condition. These are all advantages that are lacking in industrial-frequency furnaces used for residual-liquid smelting. Currently, the trend toward larger-capacity industrial-frequency induction furnaces has essentially come to a halt. However, the development of new equipment—such as thyristor medium-frequency furnaces and IGBT-based systems—as well as a series of innovative vibration-type variable-frequency medium-frequency furnaces, is thriving and gaining momentum.

A molten iron melting and holding system comprising medium-frequency induction furnaces with large tonnage or large-tonnage medium-frequency induction furnaces coupled with blast furnaces for ironmaking represents the optimal choice for energy conservation and emission reduction. This system can significantly reduce specific energy consumption, markedly lower pollutant emissions, minimize capital investment, shrink equipment installation space, and provide excellent equipment that facilitates flexible product design, process selection, and operator deployment. According to reports, when paired with other melting equipment, large-tonnage medium-frequency induction furnaces can achieve energy savings of 25% to 40% per ton of material processed. The insulated medium-frequency power supply must exhibit low melt performance, maintaining a superheat temperature of no less than 25–30°C per minute, and allow for arbitrary adjustment of power output while ensuring a power factor consistently above 92%. It should also feature precise temperature measurement and control capabilities. Since holding molten iron at temperatures above 1500°C for more than one hour can lead to the formation of white cast iron, it is crucial to continuously monitor the molten iron’s temperature and promptly adjust it downward—this can only be effectively accomplished through the advanced, intelligent, and computerized nature of medium-frequency holding power supplies. Conventional core-type power-frequency holding furnaces lack these capabilities. The series-connected variable-power supply composed of thyristors, with a power rating below 60 watts, boasts cutting-edge technology and reliable operation, fully meeting the aforementioned technical requirements. Given its exact match in specifications to the 45-ton thyristor-based medium-frequency holding furnace, large-tonnage thyristor-based medium-frequency holding furnaces are preferably equipped with thyristor technology. Series Resonant Power Supply 。