Electric Arc Furnace Bus Bar System

Electric Arc Furnace Bus Bar System

1) Characteristics of the Furnace Bus Bar

The electric furnace bus bar refers collectively to the secondary outlet terminal of the electric furnace transformer to the electrode (including the electrode).

The advantages of the furnace bus bar of the electric arc furnace are:

(1) High Current.

Due to the extremely high secondary current of the transformer, especially the frequent short-circuit impact current, the furnace bus bar has to withstand powerful currents up to tens of thousands of amperes.

(2) Short Length.

The shorter the furnace bus bar, the lower the impedance, and the smaller the power loss.

(3) Copper is Selected as the Conductor Material.

The current in the furnace bus bar is extremely high, resulting in strong electrodynamic forces between conductors. Therefore, copper with good mechanical strength and electrical performance is selected as the conductor material.The material for the secondary furnace bus bar of our 150EAF is TU2 oxygen-free copper.

The rational design and operation of the furnace bus bar are crucial for the normal operation of electric arc furnaces and the improvement of their economic and technical indicators.An advanced furnace bus bar system should ensure minimal electrical loss, high electrical efficiency and power factor, and balanced three-phase arc power.

2) Composition and Function of the Furnace Bus Bar

The furnace bus bar is primarily composed of copper head, water-cooled cable, water-cooled conductive copper tube, electrode, etc.The length of the furnace bus bar depends on the structure type of the furnace and the relative position of the furnace to the transformer.

Due to the effects of skin effect and proximity effect, when an alternating current flows through a conductor, the current density increases as one moves away from the center of the conductor's cross-section, or the current density is greater on one of the outer sides of the conductor.  Therefore, secondary short networks often employ rectangular conductors with a width-to-thickness ratio of 10 to 20, or use hollow copper tubes, rarely opting for square or round solid conductors.

The water-cooled cable is a flexible connection designed to meet the operational requirements during electrode lifting, furnace tilting, and furnace lid rotation.  Its length should only be sufficient to accommodate the required amount of expansion and contraction during these operations, and it should not be excessively long, as this would increase the impedance of the short-circuit network. The water-cooled conductive copper tube is installed above the electrode arm, with water flowing through the middle of the tube for cooling.  One end of the copper tube is connected to the water-cooled cable, while the other end is connected to the conductive copper tile via a flange.  The current in the water-cooled cable flows along the conductive copper tube to the conductive copper tile, and then to the electrode.  The design fully considers mechanical strength and current-conducting area.

Special attention should be paid to the insulation of the electrode holder.  The conductive copper tile and conductive copper tube should be well insulated from the non-current-carrying part of the electrode cross arm, otherwise the entire furnace body will become charged, causing an accident.  The insulating material is HP-5, which mainly consists of mica.