The product, which has since been installed, has enabled the Siegen steelworks, in Germany, to increase its production by 30%.
The new 105-MVA furnace transformer replaces an earlier arc-furnace transformer which had a power rating of 75 MVA.
The higher power rating of the new transformer and its higher output voltage ensure longer arcs in the furnace, thereby allowing a proportionate increase in production.
The output voltage required in each case can be set through a built-in tap changer.
A particular feature of this furnace transformer solution is a reactor that can also be adjusted through the tap changer.
This stabilises the arcs and attenuates perturbations in the power-supply system.
Exchanging the existing 26- year-old furnace transformer for a higher-powered model needed for this required the use of a series-connected transformer, also with a capacity of 105 MVA.
This transformer was connected directly to the 110-kV power- supply system and delivers the 30-kV input voltage required for operating the furnace transformer.
Although it would have been technically possible to design the input winding of the new furnace transformer for 110 kV, this would have resulted in a considerably higher transport weight and would have exceeded the carrying capacity of the steelworks crane.
The new furnace transformer, which weighs 124 t without oil, was lifted into place in the transformer house alongside the smelting furnace by crane immediately after the old transformer had been dismantled.
After it had been filled with transformer oil, the total weight of the transformer increased to about 166 t.
The cooling unit for dissipating heat loss and the expansion vessel had to be erected separately owing to lack of space.
An additional transformer house was also required for the preliminary transformer.
The plant operator, Edelstahl-werke S
Edited by: Bert Swart
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