URJA is managed by a group of technocrats having vast and varied experience in transformer design, development, production, quality control and servicing. Its modern manufacturing plant with state-of-the-art manufacturing and testing facilities as.. Read More
Industrial, Substation & Distribution Tfr. Upto 10 MVA, 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.
As cast resin transformers are solidly cast, problem associated with oil filled transformers like oil leakage and pilferage of oil is completely avoided. Due to encapsulation of coils with cast resin the coils dimensions are stable & no coil tightening is required to maintain the short circuit strength. Also no check of oil level and electrical insulationoil is required. This leads to saving in cost on account of maintenance.
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. Due to the nature of the process furnace transformers are specified with large tapping ranges. Thirty tap positions is not uncommon. Adding to the wide tapping range is the utilisation of the tap changer. Some users require up to 800 operations of the tap changer per day. This demands high maintainability and efforts to increase the maintenance intervals. On line tap changer oil filters are thus essential. To reduce downtime further, plug-in type diverters are specified. This allows a quick changeover of the diverter switch and an overhaul in a workshop environment with more time at hand.
Neutral Earthing transformers are normally provided in 3-phase system, which is without neutral and earth fault protection. Neutral earthing transformer is having zig-zag (interstar) winding to achieve the required zero phase impedance. In addition an auxiliary winding can also be provided to meet the requirement of auxiliary power supply. ONAN /ONAF cooling with conventional pressed steel radiators. The range includes up to 33 KV systems and as per the site requirements. A Earthing ( zigzag) transformer is a special purpose transformer with a zigzag or 'interconnected star' winding connection, such that each output is the vector sum of two phases offset by 120�. Its applications are for the creation of a missing neutral connection from an un-grounded, 3-phase system to permit the grounding of that neutral to an earth reference pointand also harmonic mitigation, as it can suppress triplet (3rd, 9th, 15th, 21st, etc.) harmonic currents, to supply 3-phase power as an autotransformer (serving as the primary and secondary with no isolated circuits), and to supply non-standard phase-shifted 3-phase power. Nine-winding three-phase transformers, typically have 3 primaries and six identical secondary windings which be used in zigzag winding connection as pictured. As with the conventional delta or wye winding configuration three-phase transformer, a standard stand-alone transformer containing only six windings on three cores can also be used in zigzag winding connection, such transformer sometimes being referred to as a zigzag bank. In all cases, six or nine winding, the first coil on each zigzag winding core is connected contrariwise to the second coil on the next core. The second coils are then all tied together to form the neutral and the phases are connected to the primary coils. Each phase, therefore, couples with each other phase and the voltages cancel out. As such, there would be negligible current through the neutral point, which can be tied to ground. Each of the three "limbs" are split into two sections. The two halves of each limb have the equal number of turns and they're wound in opposite directions. With the neutral grounded, during a phase to ground short fault, a third of current returns to the fault current and the remainder must go through two of the three phases when used to derive a grounding point from a delta source. If one phase, or more, faults to earth, the voltage applied to each phase of the transformer is no longer in balance; fluxes in the windings no longer oppose. (Using symmetrical components, this is Ia0 = Ib0 = Ic0.) Zero sequence (earth fault) current exists between the transformer’s neutral to the faulting phase. The purpose of a zigzag transformer in this application is to provide a return path for earth faults on delta-connected systems. With negligible current in the neutral under normal conditions, providing the defective load will be automatically disconnected in a fault condition, an undersized transformer may be used only as short time rating is required (i.e. the transformer can only carry full rated current for, say, 60 s). Impedance should not be too low for desired maximum fault current. Impedance can be added after the secondaries are summed to limit maximum fault currents(the 3Io path).
Station & Multi-winding to suit specific needs & L.T. Transformers for generating Stations. Upto 10 MVA , 3 Phase , Upto 33Kv, ONAN / ONAF / OFAF /OFWF Cooling A power transformer characterized by inner and outer low voltage winding sections and a high voltage winding section disposed there between. The low voltage windings are comprised of a plurality of pancake coils, and the high voltage winding are comprised of a plurality of conductor strands spirally wound for a plurality of coil layers. The low and high voltage winding sections are laterally spaced with the low voltage windings disposed in side-by-side positions and adjacent to the high voltage windings. The high voltage windings having a smaller turn height than the low voltage windings and having conductor strands of smaller gauge than the pancake coils of the low voltage windings. A Power transformer is an electrical device that transfers energy between two or more circuits through electromagnetic induction. A varying current in the transformer's primary winding creates a varying magnetic flux in the core and a varying magnetic field impinging on the secondary winding. This varying magnetic field at the secondary induces a varying electromotive force (EMF) or voltage in the secondary winding. Making use of Faraday's Law in conjunction with high magnetic permeability core properties, transformers can thus be designed to efficiently change AC voltages from one voltage level to another within power networks. Transformers range in size from RF transformers less than a cubic centimeter in volume to units interconnecting the power grid weighing hundreds of tons. A wide range of transformer designs is encountered in electronic and electric power applications. Generation of electrical power in low voltage level is very much cost effective. Hence electrical power is generated in low voltage level. Theoretically, this low voltage level power can be transmitted to the receiving end. But if the voltage level of a power is increased, the electric current of the power is reduced which causes reduction in ohmic or I2R losses in the system, reduction in cross sectional area of the conductor i.e. reduction in capital cost of the system and it also improves the voltage regulation of the system. Because of these, low level power must be stepped up for efficient electrical power transmission. This is done by step up transformer at the sending side of the power system network. As this high voltage power may not be distributed to the consumers directly, this must be stepped down to the desired level at the receiving end with the help of step down transformer. These are the uses of electrical power transformer in the electrical power system.Two winding transformers are generally used where ratio between high voltage and low voltage is greater than 2. It is cost effective to use auto transformer where the ratio between high voltage and low voltage is less than 2. Again three phase single unit transformer is more cost effective than a bank of three single phase transformer unit in a three phase system. But still it is preferable to use than the later where power dealing is very large since such large size of three phase single unit power transformer may not be easily transported from manufacturer's place to work site. The high reliability of these transformers ensures maximum availability, lower maintenance costs and reduced life-cycle costs. Our ultimate goal is to exceed our customers' expectations continually by delivering the highest quality services. Power transformers comply with our quality policy by:Consistent management focus on quality;Continually improving the effectiveness of our Quality Management System;Understanding our customers goals and embracing them.
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