Electric Arc Furnace Transformer Parameters & Characteristics

Electric arc furnace transformer refers to the power supply for electric arc furnaces such as various metals, ore smelting, heat treatment, preparation of alloys, and electroslag return.

The electric arc furnace transformer is one of the main electrical equipment of the electric arc furnace. Its function is to reduce the input high voltage of up to 10-110kV (or even higher) to 100-1200V and then output it to generate a large current to power the arc furnace.

Parameters:

The main parameters of the electric arc furnace transformer are as follows:

(1) Primary rated voltage.

This voltage is the voltage applied by the power supply network to the primary coil of the transformer, that is, the standard voltage of the power supply network, mainly including 6kV, 10kV, 35kV and 110kV.

(2) Secondary voltage.

The secondary voltage is also known as the low-side voltage. Its size and its series mainly depend on the requirements of the steelmaking process, and its range is generally between 100 and 1200V.

(3) Rated current.

No matter how the transformer is connected, the rated current in the low-voltage side coil remains unchanged; while the current in the high-voltage coil changes with the change of the secondary current.

(4) Rated capacity.

The capacity at the highest secondary voltage is defined as the rated capacity of the electric arc furnace transformer.

(5) Power supply frequency.

In my country, the power frequency f=50Hz, but in foreign countries, the regulations of the power frequency are different in different countries.

(6) The connection line and connection group of the coil.

When the coils are connected in a Y-△ shape or a △-△ shape, the connection group is marked as Yd11 (11 means the primary and secondary phase angles differ by 11°) or Dd0 (0 means the primary and secondary phase angles differ by 0°).

(7) Efficiency.

Generally, η = 95% to 98% for small and medium-sized transformers, and η = 99% for large transformers.

Characteristics:

The load of the electric arc furnace transformer changes with time, and the current fluctuates greatly. Especially during the melting period, the electric arc furnace transformer is often in a peak load with a large inrush current. Compared with ordinary power transformers, electric arc furnace transformers have the following characteristics:

(1) The transformation ratio is large, the primary voltage is high and the secondary voltage is low.

(2) The secondary current is large, up to several thousand to one million amperes.

(3) The secondary voltage can be adjusted to meet the needs of the smelting process.

(4) The overload capacity is large, and the transformer is required to have a short-time overload capacity of 20%, which will not affect the life of the transformer due to the general temperature rise.

(5) It has high mechanical strength and can withstand the mechanical stress caused by impulse current and short-circuit current.

(6) The maximum temperature of the transformer is less than 95°C during operation.

(7) It is stipulated that the primary (high voltage) coil of the electric arc furnace transformer can be connected to both a Y shape and a △ shape, while the secondary (low voltage) coil can only be connected to a △ shape.

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