Furnace Transformer

The transformer for electric arc furnace steelmaking shall be able to adjust the voltage and current separately according to the smelting requirements, and be able to withstand the impact of working short-circuit current.

There are many factors to be considered in the selection of the rated voltage of the furnace transformer. If the primary side voltage is higher, the system has small reactance and large short-circuit capacity, which can reduce flicker, but the cost of the power distribution device must be increased. If the secondary voltage is higher, the power factor is higher and the electric efficiency is higher, but the arc is longer, the furnace wall loss is faster and the comprehensive efficiency is lower.

Generally, the secondary side of the furnace transformer is low voltage (tens to hundreds of volts) and high current (thousands to tens of thousands of AMPS). In order to ensure the different needs of electric power in each smelting stage, the secondary voltage of the transformer should be adjustable in the range of 50% ~ 70%, so it is designed as a multi-level adjustable form. The adjustment methods include transformation, on-load tap changer, etc. If the transformer capacity is less than 10MVA.

On load switching; for capacity above 10MVA, load voltage regulation shall be adopted generally. There are also three-phase taps, which can be adjusted to ensure the three-phase heat balance in the furnace.

Compared with the common power transformer, the special transformer for the electric furnaces has the following characteristics: A. It has a larger overload capacity;

1. It has higher mechanical strength;
2. It has a larger short circuit impedance;
3. It has several secondary voltage levels;
4. it has a larger transformation ratio;
5. it has lower secondary voltage and a larger current.

The capacity ratio of electric arc furnace transformer and electric arc furnace is generally 0.4 ~ 1.2mva/t. The current control of the EAF is achieved by the switch of the high voltage side winding tap of the EAF transformer and the rise and fall of the electrode.