The rectifier is the core equipment of the electrolytic aluminum plant. Once it is put into operation, no longer shutdown is allowed. This article focuses on the application of fast fuses in high-power rectifier equipment in the electrolytic aluminum industry.
1 Introduction
High-parameter fast fuse is mainly used for the protection of high-power semiconductor equipment. A typical semiconductor device of this type is a high-power rectifier that uses diodes or thyristors to convert AC power to DC. There are many industrial applications of high-power rectification, and this article mentions only some of them.
2. High-power rectifier applications
Aluminum electrolysis Metal aluminum is mainly produced by electrolysis. Many aluminum factories in the world are expanding their production scale to improve efficiency and meet the market's demand for aluminum. The process of aluminum electrolysis is that aluminum oxide (Al2O3) undergoes an electrolytic reaction in the electrolytic cell to generate aluminum and oxygen: 2 Al2O3+3C→4Al+3CO2
The electrolytic cell is a large and shallow steel tank with a carbon layer on the inside. Different electrolytic cells are electrically connected in series. In each electrolytic cell, the direct current flows into the molten alumina electrolyte through the graphite anode, and then flows out through the carbon cathode lining the electrolytic cell, and enters the anode of the next electrolytic cell, and so on. Under the action of the electric current, the oxygen element in the alumina is separated and combined with carbon in the upper part of the electrolytic cell to form carbon dioxide, and liquid aluminum is deposited at the bottom of the electrolytic cell.
Chlorine electrolysis Usually chlorine is obtained from the electrolysis of brine, and hydrogen and caustic soda are simultaneously produced. It takes about 4000 degrees of electricity to produce one ton of chlorine. The DC process current required for the chlorine electrolysis process is between 300-350kA, and the required DC voltage can be as high as 1000Vdc.
DC Electric Arc Furnace Many large modern steel plants use DC electric arc furnaces to melt recycled scrap steel. The advantages of using DC electric arc furnace are large production capacity, high production efficiency and low noise. The process current of the electric arc furnace for iron and steel smelting is about 100kA, and the voltage is generally higher than 1000Vdc. The electrolysis process is generally clean, and the continuous load current flows steadily through the semiconductor and the fuse. The application of electric arc furnaces is different. The characteristics of their production process make the load current often have serious pulse components, so very careful calculation and verification are required when selecting semiconductors and fuses.
Graphite furnace The production of many graphite products, such as electrodes, also uses a direct current furnace. Typical process parameters are: the voltage is generally not higher than 300V, and the current may be as high as 160kA. Other metal smelting Process currents in the production of metals such as copper, zinc, lead, nickel, and cadmium also need to be generated by a high-power rectification process.