There are two basic types of electromagnetic casting, vertical and horizontal, and the vertical electromagnetic casting can be divided into pull-up and pull-down. At present, the electromagnetic casting that has been put into industrial production on a large scale in the world is all down-quoted. Therefore, this book mainly introduces the electromagnetic casting device of vertical down-draw aluminum and its alloys.
8. 1. 2. 1 Power supply device and its system
The power supply device is an important equipment of electromagnetic casting, including intermediate frequency generator set or thyristor intermediate frequency power supply. The former Soviet Union, Hungary, Czech Republic, Germany and other European countries adopted intermediate frequency generator sets in the early stage, and a set of generator sets can only cast one ingot. After the 1970s, countries such as Switzerland and the United States applied thyristor intermediate frequency power supplies to electromagnetic casting technology, and a set of power supplies can cast multiple ingots. The thyristor intermediate frequency power supply has many advantages over intermediate frequency generator sets, so it is widely used.
The principle of the electromagnetic casting power system is shown in Figure 8-6.
Figure 8-6 Schematic diagram of power supply system
1-square aluminum ingot; 2-mold induction coil; 3-intermediate frequency transformer; 4-compensation capacitor;
5—Inverter circuit; 6—Smoothing inductor; 7—Rectification circuit; 8—Three-phase AC current
The thyristor intermediate frequency power supply is a device that converts three-phase power frequency alternating current into intermediate frequency alternating current. It uses an AC-DC-AC frequency conversion circuit, which is characterized by having a tributary intermediate link. Through the rectifier circuit, the power frequency AC power is first converted into DC power, and then the DC power is converted into AC power with a frequency of / through the inverter circuit. The thyristor intermediate frequency power supply has the advantages of simple circuit, convenient debugging, reliable operation, and efficiency above 90%. Devices with different capacities have slightly different control loops and different structures, but the principle is the same.