What are the requirements for the output frequency of high-frequency annealing power supply for induction furnace?

There is a correlation between the electrical efficiency of an induction furnace and its frequency. If the output frequency of the high-frequency annealing power supply can be determined based on electrical efficiency, the power can be called f0. The inductor is actually an inductance coil. In order to compensate for the infinite power of the coil, capacitors are connected in parallel at both ends of the coil. This forms an LC oscillation circuit. When the output power f of the inverter is equal to the natural oscillation frequency f0 of the induction furnace circuit , and at this time the power factor of the loop is equal to 1, and greater power will be obtained in the induction furnace. Since the natural oscillation frequency of the loop is related to the values of L and C, the value of the compensation capacitor C is generally fixed, while the inductor L changes due to changes in the magnetic permeability of the charge. For example, when steelmaking is in a cold furnace, the magnetic permeability of the steel is very large, so the inductance is large. When the temperature of the molten steel is higher than the Curie point, the magnetic permeability of the steel is 1, so the inductance L decreases, so the inherent resistance of the induction furnace circuit The oscillation frequency f0 will change from low to high. In order to ensure that the induction furnace can always obtain a larger edge rate during the melting process, this requires that the output frequency f of the high-frequency annealing power supply changes with the change of f0 and always maintains automatic frequency tracking.

In addition to the requirements for output power and output frequency, high-frequency annealing power supplies also have other performance requirements.

During the smelting process of the induction furnace, once the high-frequency heating power supply fails, the crucible will be damaged in severe cases. Therefore, the high-frequency heating power supply is required to work reliably, and it must have the necessary voltage limiting, current limiting performance, and overvoltage, Overcurrent protection, water cutoff protection, furnace leakage protection (furnace lining thickness detection) and other automatic protection devices. In addition, the high-frequency annealing power supply is also required to have a high start-up success rate, even up to 99%, and to facilitate start-stop operations.