The thyristor intermediate frequency induction heating power supply, also known as the thyristor intermediate frequency power supply, is the main induction heating power source in the 0.4~10KHz frequency band, and is also the power source for most steel induction heating rapid heat treatment. There are two types of thyristor intermediate frequency power supply from the power supply from the circuit structure, namely parallel inverter intermediate frequency power supply and series inverter intermediate frequency power supply. These two intermediate frequency power supplies have been mass produced and widely used in China.

Thyristor parallel inverter medium frequency induction heating power supply

The thyristor parallel inverter intermediate frequency power supply has the advantages of strong load adaptability, stable and reliable operation, good overcurrent protection characteristics, and large power supply. It is the most widely used intermediate frequency power supply.

The basic structure of the power circuit is the basic structure of the thyristor parallel inverter IF power supply circuit. The three-phase bridge type full-controlled rectifier circuit is composed of VR1~VR6, and the rectified DC power is filtered by the inductor coil filter Ld, and then input into the inverter circuit composed of the thyristors VR7~VR10. The rectifier circuit controls the thyristor conduction angle a in a phase-controlled manner to adjust the output voltage Ud. The load circuit is composed of a compensation capacitor Ch and an inductive load LH in parallel.

The working principle of the inverter circuit The inverter circuit converts the DC power Id into the VR7~VR10 thyristor and converts it into an intermediate frequency current supply circuit with frequency f. Before introducing the principle of inverter, let's first understand the relationship between the period T of the alternating current and the frequency f. Inverter is to convert DC power into AC with sinusoidal waveform with period T. The current f of the intermediate frequency band is 0.4~10KHz, and its T value is 4*10-2~10-4s. The working principle of the thyristor inverter circuit is described below. Assume that during 0<t<T/2, VR7 and VR9 are turned on, and VR10 is turned on; and VR9 is turned off. At this time, the inverter circuit outputs an alternating current of Id and current frequency f=1/T. This is the simple working principle of the thyristor inverter circuit. For details, please refer to the professional electronic power technology literature (the following types of inverter circuits are the same, do not repeat)

Application of thyristor parallel inverter medium frequency induction heating power supply This type of medium frequency induction heating power supply is suitable for steel continuous heat treatment production line power supply due to its strong load adaptability and inconvenient starting operation. In addition, its large capacity, stable and reliable work, it is suitable for seamless steel pipe induction heating and quenching and tempering processing line power supply. In short, the thyristor parallel inverter medium frequency induction heating power supply can be used as the main power source for rapid heat treatment of steel continuous induction heating.

Thyristor series inverter medium frequency induction heating power supply

The thyristor series inverter IF power supply circuit has the characteristics of simple circuit, easy startup, constant output power, etc., but the overcurrent protection performance is slightly poor.

The basic structure of the power circuit, the basic structure of the thyristor series inverter IF power circuit. The rectifier circuit consists of a three-phase bridge rectifier current circuit composed of VD1~VD6 diodes, which rectifies the three-phase AC power of the grid into single-phase DC power, and is filtered by Cd into a smooth DC voltage Ud. Ud is applied to the input terminal of the inverter circuit composed of thyristors VR1 to VR4 and diodes VD1 to VD4. Ld is used to limit the peak size of the rectifier bridge to the Cd charging current. The main circuit is simplified due to diode rectification. However, Ud is a constant DC voltage, which is not adjustable, so its output power is constant, which is one of the characteristics of the series inverter IF power supply.

The working principle of the inverter circuit assumes that VR1~VR3 are turned on and VR2~VR3 are turned off during 0<t<T/2, then the output voltage of the inverter circuit is Ud?, and the frequency is f=1/T. The phase changes with the phase of the inverter output current iH, which is the working principle of the series inverter circuit.

The application of thyristor series inverter IF induction heating power supply, this type of IF induction heating power supply is suitable for frequent starting conditions due to its constant output power and convenient starting. For smelting, billet heating, surface quenching, heat treatment of short materials, etc., it is suitable to use, such as heat treatment of steel, such as cold drawing material recrystallization annealing, such intermediate frequency power supply can be used.

Transistor super audio induction heating power supply

Transistor super-audio induction heating power supply refers to a power supply with a frequency of 10~100KHz and a new transistor to form an inverter circuit. IGBT transistors (insulated gate bipolar transistors) are representative of transistors, IGBT transistors with MOS devices and bipolar devices: low on-state voltage, high input impedance, fast switching speed and strong current capability. The inverter circuit power supply constructed by such a device is called an IGBT super audio induction heating power source.

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