Characteristics and classification of intermediate frequency power supply for induction melting furnace

    The intermediate frequency power supply of the induction melting furnace is a static variable frequency power supply composed of power semiconductor components. It has two modes: AC-DC-AC and AC-AC. This is only the former, which is the most commonly used medium frequency power supply for medium frequency melting furnaces.

    Compared with the traditional medium frequency power generator set, the intermediate frequency power supply has the advantages of high efficiency, variable frequency, low noise, small size, light weight, easy installation, and easy operation and maintenance.

    Compared with power frequency induction furnaces, medium frequency induction melting furnaces have significant advantages in terms of operational flexibility and economy. Mainly in the following aspects.

    1 high power density, high melting rate and thermal efficiency.

    2 The electric furnace can be emptied, no need to leave the molten liquid, and it is easy to replace the metal type.

    3 The wet or oily charge does not need to be dried, and can be directly charged into the furnace for melting.

    4 It can automatically change the frequency to adapt to the change of the material parameters. It is not necessary to use the contactor to cut the capacitance to compensate the power factor like the power frequency induction furnace.

    5 At the same productivity, the volume of the medium frequency induction furnace body is small, so the heat loss and the thermal stress of the lining are also small, and the service life of the lining is prolonged.

    6 No need for easy-to-failure pressure regulating switches to reduce maintenance workload.

    7 does not require a three-phase balancing device.

    8 small footprint, less civil engineering and installation costs.

IF power supplies also have certain shortcomings. Harmonics and noise generated by high-power IF power supplies can interfere with the power grid and the environment, and measures must be taken to solve them.

Depending on the filter used, the IF power supply can be divided into current type and voltage type. The current type is filtered by DC smoothing reactor to obtain a relatively straight DC current. The load current is a rectangular wave, and the load voltage is approximately sinusoidal. The voltage type is capacitor filtered to obtain a relatively straight DC voltage. For rectangular waves, the load supply is approximately sinusoidal.

According to the load resonance mode, the intermediate frequency power supply can be divided into three types: parallel resonant type, series resonant type and series-parallel resonant type.

The current type is often used in parallel and series-parallel resonant inverter circuits, and the voltage type is mostly used in series resonant inverter circuits.

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