What are the classifications of electric furnace transformers?
Electric furnace transformers are transformers designed to provide power for various electric furnaces. Industrial electric furnace transformers can be roughly divided into three categories: resistance furnace transformers, electric arc furnace transformers and induction furnace transformers. Let me tell you what these three types of transformers are. ?
1. Resistance furnace transformer
Resistance furnaces and salt bath furnaces used for heating of mechanical parts, heat treatment, powder metallurgy sintering, non-ferrous metal smelting, etc. Because the resistance of the heating element is too small, or the resistance of the heating element changes too much during the heating process, it needs to be heated in the furnace. A resistance furnace transformer is equipped between the power grid and the power grid to reduce and adjust the input voltage of the electric furnace.
Small-capacity, low-voltage resistance furnace transformers and salt bath furnace transformers are mostly dry-type transformers, with box shells, and natural cooling; medium-capacity (hundreds of thousands of VA) resistance furnace transformers are mostly oil-immersed self-cooling transformers; The larger capacity is the forced oil circulation water-cooled transformer.
2. Electric arc furnace transformer
A special transformer for powering electric arc furnaces used in iron and steel smelting. It has large capacity, complex structure and high technical requirements. Its secondary voltage is low, generally from tens of volts to hundreds of volts, and it is required to be adjustable within a large range; The secondary side current often reaches thousands of tens of thousands of amperes. In addition, in steel smelting, the melting period requires high power, and the transformer is required to have an overload capacity of 20 percent within 2 hours. In the steelmaking process, the collapse of the charge is likely to cause electrode damage Therefore, the primary side of the arc furnace transformer should be connected with a current-limiting reactor, or it should have a large impedance to limit the short-circuit current.
3. Induction furnace transformer
The winding of the shell-type electric furnace transformer is a rectangle with the same cross-sectional shape as the core column. The low-voltage winding is made of a single piece of copper plate, with good heat dissipation conditions, and the outlet is a welded structure; the high-voltage winding is a cake-type structure. The high-voltage line segment and the low-voltage line segment should have the same magnetic potential, and their radial dimensions should be basically the same. Theoretically, the low-voltage line segment should be placed on the 2 end, because the insulation distance to the iron core is small. However, in order to make the short-circuit impedance of the transformer smaller, it is necessary to Multiple magnetic flux leakage groups can meet the requirements, and placing the low-voltage line segment on the 2 end will limit the number of magnetic flux leakage groups, so sometimes the high-voltage line segment is placed on the 2 end. During the voltage regulation process, in order to make the line segment configuration symmetrical and ensure the In order to ensure the potential balance, the voltage regulation line segment usually adopts multiple parallel connections, so as to ensure that the impedance of each leakage flux group is equal, and the current of each low-voltage line segment is also equal.
