Heating coils are lightweight, quiet and reliable in operation

The conductor itself is heated by the thermal effect formed by the induction current (eddy current) generated by the conductor in the alternating electromagnetic field. According to different heating process requirements, the frequencies of AC power used in induction heating include power frequency (50-60 Hz), intermediate frequency (60-10000 Hz) and high frequency (higher than 10000 Hz). The power frequency power supply is the AC power supply usually used in industry, and the power frequency in most countries in the world is 50 Hz. The voltage applied to the induction device by the power frequency power supply for induction heating must be adjustable. According to the power of the heating equipment and the capacity of the power supply network, a high-voltage power supply (6-10 kV) can be used to supply power through a transformer; the heating equipment can also be directly connected to a 380-volt low-voltage power grid.
The intermediate frequency power supply has used the intermediate frequency generator set for a long time. It consists of a medium frequency generator and a drive asynchronous motor. The output power of this unit is generally in the range of 50-1000 kilowatts. With the development of power electronics technology, the intermediate frequency power supply of thyristor inverter is used. This kind of intermediate frequency power supply uses thyristors to convert power frequency alternating current into direct current, and then convert direct current into alternating current of required frequency. Due to the small size, light weight, no noise and reliable operation of this kind of frequency conversion equipment, it has gradually replaced the intermediate frequency generator set.
The high-frequency power supply usually uses a transformer to raise the three-phase 380-volt voltage to a high voltage of about 20,000 volts, then uses a thyristor or a high-voltage silicon rectifier element to rectify the power-frequency alternating current into direct current, and then uses an electronic oscillation tube to Direct current is converted to high-frequency, high-voltage alternating current. The output power of high-frequency power supply equipment ranges from tens of kilowatts to hundreds of kilowatts.
Objects to be heated by induction must be conductors. When high-frequency alternating current passes through the conductor, the conductor produces a skin effect, that is, the current density on the surface of the conductor is large, and the current density in the center of the conductor is small.
Induction heating can be used for overall uniform heating and surface heating of metal objects; it can be used for smelting metals, it can be used for metal brazing, it can be used for various heat treatments (quenching, tempering, normalizing) and forging, and it can be used for forging. Frequency band, changing the shape of the heating coil (also known as inductor), can also perform arbitrary local heating.