minthas.blogg.se - Que trabajo hace un transformer en un furnace

Provides heating in the winter and cooling in the summer.

Upper levels for impedance could be any value from 10 to 24 % depending on the configuration and tapping range. To achieve lower values, one would need a shell type transformer. Minimum impedance values for furnace transformers of the core type are in the order of 4 – 5 %. A very robust design in terms of the transformers’ ability to withstand the dynamic effects of repeated short circuits is required. This gives rise to higher over-current factors. To add to this peril, furnace transformers are required to have a lower than normal impedance. Bus-bar flashovers are also a fact of life on most furnace installations. Transformers associated with open arc furnaces can be subjected to a number of short circuits per melt as the material being melted collapses across the electrodes.

This allows a quick changeover of the diverter switch and an overhaul in a workshop environment with more time at hand.Īnother aspect of the process is the large number of short circuits that these transformers are subjected to every day. To reduce downtime further, plug-in type diverters are specified. On line tap changer oil filters are thus essential. This demands high maintainability and efforts to increase the maintenance intervals.

Some users require up to 800 operations of the tap changer per day. Adding to the wide tapping range is the utilisation of the tap changer. Large inspection covers in close proximity to the tap changer are often specified.ĭue to the nature of the process furnace transformers are specified with large tapping ranges. This in turn calls for good accessibility of the tap changer and other parts of the transformer. When shutdowns occur, the problem needs to be solved quickly. Shutdowns due to transformer problems are frowned upon. Loading of these transformers is then very close to rated values and even beyond. To reduce the fire risk the transformers are contained in rooms, which adds to the high ambient temperature.įurnace transformers are very much in a production environment. The location above ground level encourages single phase units due to the structural limitations of the buildings.

This means that there is a high risk of fire, a high ambient temperature and this whole set up is located at a level associated with the third story of the building. The furnace transformers are then located close to the furnace itself and if they are single phase units, arranged in a triangle around the furnace. Furnace bus-bars are mostly water cooled.ĭue to the high secondary currents and resistive losses the furnace layout is such as to limit the bus-bar length. These bushings are specified with very specific arrangements to suit the bus-bar arrangement and cooling system. For these high secondary currents special bushings are required to connect to the bus-bars. As an example a 30 MVA unit at 150 V would result in a secondary current of 115 kilo Ampere. This results in massive secondary currents. Bus bar terminals are mounted exterior to the enclosure for providing electrical connection with the low-voltage windings.įurnace transformers are used to step down from voltages between 11 and 33 kV to levels of several hundred volts only. Arc, Submerged Arc, Ladle, Induction, Upto 10 MVA,Upto 33kV,ONAN/OFWF Cooling A high current furnace transformer is provided having the low-voltage windings arranged in a closed delta configuration within the transformer enclosure.