Parallel inverter medium frequency power supply is generally used in the field of medium frequency induction heating

Introduction of Medium Frequency Induction Heating Power Regulator

The power regulating device for induction heating is a medium frequency induction heating power regulating device with high power factor. At present, in the field of intermediate frequency induction heating, parallel inverter intermediate frequency power supplies are commonly used. The most common way of power regulation is to change the control angle α of the three-phase bridge type fully-controlled rectifier device, thereby changing the DC output voltage to achieve the purpose of adjusting the output power. . The power factor of its rectifier circuit COSφ=COS(α+γ/2), where α——control angle, γ——commutation angle. That is to say, when the commutation angle γ is constant, the power factor COSφ decreases with the increase of α. When the equipment is working, it is necessary to ensure that the rectifier circuit has an appropriate power factor COSφ, so it is not suitable to work in the state of deep control. During the working process of the intermediate frequency power supply of the existing intermediate frequency diathermy and smelting heating device of Shenguang Furnace, the rectification is in the deep control state for only a small proportion of time, so even the large-capacity intermediate frequency power supply has not taken measures against it. However, when there are different heating temperature requirements, especially when the heating temperature is required to have a large difference, for example, when performing intermediate frequency quenching and tempering treatment on the workpiece, due to the large difference between quenching and tempering temperatures, the difference between the intermediate frequency power required by the two is within two If the same set of inductors is used for quenching and tempering, and the power is adjusted by changing the rectification control angle α, then the power factor will be greatly reduced, and the long-term operation of the equipment in this state will not be allowed . How to provide a medium-frequency induction heating power adjustment device that can adjust power in a wider range under the condition of maintaining a high power factor? The mid-frequency induction heating power adjustment device in the medium-frequency induction heating includes an inverter resonant circuit composed of a capacitor bank and an inductor. The special feature of the capacitor we use here is that there are a first capacitor bank and a second capacitor bank. The first capacitor bank and the inductor The inductor is connected in parallel with the second capacitor bank after being connected in series, and a switch capable of short-circuiting the capacitor bank is provided at both ends of the first capacitor bank. That is, the first capacitor bank and the inductor are connected in series to form a series resonant circuit. Through the above switch, the capacitance of the first capacitor bank can be switched in different combinations, and the voltage at both ends of the inductor can be changed, so as to achieve the purpose of adjusting the heating power of the inductor. . The above-mentioned switch may be a switch for short-circuiting all the capacitors of the first capacitor bank, or a switch for short-circuiting part of the capacitors of the first capacitor bank. For a high-power intermediate frequency heating device, the above-mentioned switch is preferably a water-cooled switch. The advantages of this new device are small investment, high efficiency, simple structure and reliable operation. In addition, this new type of Shenguang furnace also has the advantages of easy start-up of series inverters and good load adaptability of parallel inverters, especially through reasonable configuration of series capacitors and parallel inverters without the need for intermediate frequency transformers. The ratio of capacitors can be used to obtain an economical and reasonable inductor coil voltage.