Reliance Transformers

Panoli GIDC, Bharuch, Gujarat

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. Bus bar terminals are mounted exterior to the enclosure for providing electrical connection with the low-voltage windings. Furnace transformers are used to step down from voltages between 11 and 33 kV to levels of several hundred volts only. This results in massive secondary currents. As an example a 30 MVA unit at 150 V would result in a secondary current of 115 kilo Ampere. For these high secondary currents special bushings are required to connect to the bus-bars. These bushings are specified with very specific arrangements to suit the bus-bar arrangement and cooling system. Furnace bus-bars are mostly water cooled. Due to the high secondary currents and resistive losses the furnace layout is such as to limit the bus-bar length. 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. 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 location above ground level encourages single phase units due to the structural limitations of the buildings. To reduce the fire risk the transformers are contained in rooms, which adds to the high ambient temperature. Furnace transformers are very much in a production environment. Loading of these transformers is then very close to rated values and even beyond. This demands very reliable transformers. Shutdowns due to transformer problems are frowned upon. When shutdowns occur, the problem needs to be solved quickly. This in turn calls for good accessibility of the tap changer and other parts of the transformer. Large inspection covers in close proximity to the tap changer are often specified.

Industrial, Substation & Distribution Tfr. Upto 22kV, Upto 11kV, Upto 33kV, ONAN A poly phase Distribution Transformers design is presented in which transformer output pores are accurately constructed in both voltage magnitude and relative phase angle. The design incorporates both main and auxiliary transformers that are used in unison to produce the accurately constructed phases. The main transformer permits rough phase adjustment to be made with the auxiliary transform permitting phase fine tuning. Such a design is particularly suitable in transformer approaches that require output phases that are of a number not evenly divisible by three. Distribution transformers normally have ratings up to 2500 kVA, although some national standards can describe units up to 5000 kVA as distribution transformers. Since distribution transformers are energized for 24 hours a day (even when they don't carry any load), reducing iron losses has an important role in their design. As they usually don't operate at full load, they are designed to have maximum efficiency at lower loads. To have a better efficiency, voltage regulation in these transformers should be kept to a minimum. Hence they are designed to have small leakage reactance. Distribution transformers are classified into different categories based on certain factors such as: • Mounting location - pole, pad, underground vault   • Type of insulation - liquid-immersed or dry-type   • Number of Phases - single-phase or three-phase   • Voltage class   • Basic impulse insulation level (BIL).