How to choose a high-quality induction melting furnace?
1. The rectifier circuit of the induction melting furnace is a bridge rectifier, which is divided into three phases and six phases. Among them, the three-phase bridge rectifier circuit is composed of three groups of thyristors, commonly known as six-pulse rectification; the six-phase bridge rectifier circuit is composed of six groups of thyristors, commonly known as twelve-pulse rectification; it is also used in high-power induction melting furnaces. There are twenty-four pulse rectification or forty-eight pulse rectification.
The working principle of the rectifier circuit of the induction melting furnace is to arrange the corresponding thyristor to be turned on and off at the right time according to a certain rule, and finally realize the conversion of three-phase alternating current into direct current.
2. The inverter circuit of the induction melting furnace is to convert the rectified direct current into a higher frequency alternating current to supply the coil load, so this induction melting furnace inverter is actually an “AC-DC-AC” process.
The inverter circuit of the induction melting furnace is divided into a parallel resonance inverter furnace and a series resonance inverter circuit. The parallel resonant inverter circuit is widely used, and almost all of the early induction melting furnaces use this control circuit, which is relatively mature. The disadvantage is that the power factor increases with the increase of the charge, and the general power factor is about 0.9; the series inverter induction melting furnace has appeared in the past ten years, and the advantage is that the power factor is high, generally above 0.95 , can realize two furnace bodies work at the same time, so it is called one-for-two melting furnace in the foundry industry.
3. For the filtering of the induction melting furnace, due to the large fluctuation of the rectified voltage, it is necessary to connect a large inductor in series in the circuit to make the current smoother, which can make the voltage with large fluctuations smoother. This is called filtering. This inductance is usually called a reactor. The characteristic of the reactor is to keep the current from sudden change.
The induction melting furnace is supplied to the inverter circuit through the smoother DC power after filtering. Series devices are filtered with capacitors to obtain a smoother voltage.