Design Of The 3500kW Mid-Frenquency Induction Furnace System Of Series-Resonance

As the new industrial methods, induction melting and heating has been widely used in the past 30 years. Mid-frequency induction furnace smelting required high-power input and continuous batch of hot metal output, the energy saving indicators of furnace, reliability and reducing the harmonic pollution become the new research topic. The key technology of furnace is mid-frequency power, the parallel resonant inverter mid-frequency power is widely used currently. It has simple structure and low cost, but has low power factor and low efficiency of energy use, compared to the series resonant frequency power supply. The technical of the series resonant frequency power supply is complexity, and comes from foreign (US INDUCTOTHERM company), and its production and development has a certain degree of technological bottlenecks in the domestic furnace company. So based on the theory of the series resonance energy-saving of the Cui Jingping’s Vol, the paper designed the system of the series resonance mid-frequency furnace, that is 5 tons capacity. The main research works is:1. Analysised of the work principle of the series resonance mid-frequency furnace, including the principle of the induction heating and the introduction of the induction loop load;2. Designed the main circuit of the series resonance mid-frequency furnace system, including rectifier circuit and inverter circuit, and further elaborated its principle of the power regulating and energy-saving;3. Designed the control circuit of the series resonance mid-frequency furnace system, including rectifier control circuit and inverter circuit, the rectifier digital phase circuit and the inverter trigger circuit;4. Designed the protection circuit, including input line over-current protection, mid-frequency over-current protection, and mid-frequency overvoltage protection, and analyzed the problem of thyristor current sharing and dynamic protection;5. Based on the energy conservation principle, researched the parameter matching of the mid-frequency power and induction loop(load),and proposed the design principle of the energy-saving matching;6. Data of the actual operation showed, this system completed of the basic functions of the mandate, achieved the desired effect of energy saving.