How to adjust the voltage of arc furnace transformer?
Recently, TBEA announced its 2005 interim report. The results in the first half of the year were mediocre, with no bright spots. Similarly, Xuji Electric's semi-annual report showed that although the main business income increased by 7.56% compared with the same period last year, the profit decreased by 20.65%. During this period, the profit of the transformer business has dropped significantly. It is affected by factors such as the increase in raw material prices and the increase in financing costs.
The characteristics of the transformer manufacturing industry are that the delivery cycle is relatively long, generally 36 months, and even more than 1 year. Some contracts of large enterprises such as TBEA and Tianwei Baobian have even been signed in 2007. The production tasks of Xidian Group, a major transformer manufacturer, are also very full.
A special electric arc furnace transformer for powering electric arc furnaces used for steel tempering. It has large capacity, complex structure and high skill requirements. Its secondary voltage is low, generally from tens of volts to hundreds of volts, and it is required to be able to operate within a large range. Conditioning; the secondary side current often reaches thousands to tens of thousands of amps. In addition, in the steel tempering, the melting period requires high power, and the transformer is required to have a 20% overload capacity within 2 hours. In the steelmaking process, due to the collapse of the charge It is easy to form an electrode short circuit, so the primary side of the arc furnace transformer should be connected in series with a current limiting reactor, or make it have a large impedance to constrain the short circuit current.
When the electric furnace is running, it is also required that the power supply transformer can regulate the voltage. There are two methods of regulating the voltage of the electric furnace transformer.
On the primary winding of the electric arc furnace transformer, the lead-out tap is connected to the tap changer. △-Y switching can also be used between the three phases of the primary side to complete the secondary voltage regulation. △-Y switching is a very economical voltage regulation method. On the basis of not changing the number of turns on the primary side, the secondary side voltage can be reduced to the original 1\/. Because each phase winding has 9 taps, plus △-Y switching, a total of 29 or 18 levels of voltage can be obtained.
Main transformer 1 is a 3-winding transformer, winding 1 is a high-voltage winding connected to the power grid; winding 2 is a winding with taps, which is connected in series with the primary winding 4 of series transformer II through a fire switch; winding 3 is connected to the secondary winding of series transformer II. Winding 5 is connected in series to supply power to the load of the electric furnace. By changing the primary voltage of the series transformer II through the fire switch, the output voltage of the 3 and 5 windings can be changed. The 3 and 5 windings connected to the load generally only need 1-2 turns , generally made of copper or aluminum plate 8-shaped coil.
However, the prices of the products in the contract were calculated based on the prices of raw materials at that time. Most manufacturers did not expect that the prices of raw materials would rise so rapidly. Therefore, their achievements were not fully reflected. Recently, Wuhan Iron and Steel Co., Ltd. Adjusted the sales prices of some products in September this year. Under the background of the price reduction of various steel products, the price of oriented silicon steel sheets has been increased by 2,000 yuan \/ ton, and further price increases are not ruled out.
