Construction of hearth and lower side section of the shell of larger diameter than the top opening. This leads to increase in shell volume which results in larger tonnage charge, lower heat losses and improved thermal efficiency.
In the split shell design, shell structure is constructed in two sections: lower section which contains hearth and free board allowance for slag, and upper section containing side wall and roof. The two sections are coupled such that the upper section can be repaired easily. This reduces the downtime and increases furnace availability.
High powered transformers are the current trends. Most modern furnaces operate at and the trend is towards ultra high power ranging in between to. Developments are in progress to install transformer with capacity. It is claimed that a 120 tons operating at transformer capacity and by using refining combined burner technology through oxygen gas and carbon injection, it is possible to increase capacity by up to 50%. The largest transformer in AC EAF corresponds to a rated power 0f for 300 ton furnace.
Eccentric bottom taping reduces tap times, temperature losses and slag carry over into ladle. The strip producing plants are equipped with eccentric bottom tapping in electric arc furnaces.
DC (direct current) arc furnaces represent a different concept in arc furnace design. Most DC furnaces are with single electrode where current flows down from the carbon electrode to an anode mounted in the bottom of the furnace. Reduced electrode consumption of the order of 50 to 60 % is the major benefit of a dc furnace compared to a convectional three- phase arc furnace. Noise levels for the dc furnaces are lower. Lower maintenance costs are claimed and refractory costs are less for sidewall but more for the furnace bottom. A dc arc furnace requires an addition of the bottom electrode (anode), a dc reactor, and a thyristor all of which add cost to a dc furnace. The electrode technology limits diameter to a maximum of 700 mm allowing a dc current of 100kA and 7 power for single electrode furnace. Furnace size is limited to 200 tons. Further developments are in progress.
and the trend is towards ultra high power ranging in between 
to
. Developments are in progress to install transformer with 
capacity. It is claimed that a 120 tons operating at 
transformer capacity and by using refining combined burner technology through oxygen gas and carbon injection, it is possible to increase capacity by up to 50%. The largest transformer in AC EAF corresponds to a rated power 0f 
for 300 ton furnace. 
power for single electrode furnace. Furnace size is limited to 200 tons. Further developments are in progress.
