A Transformer is a static piece of apparatus used for transferring power from one circuit to another without change in frequency. It can raise or lower the voltage with a corresponding decrease or increase in current.
The basic principle of a transformer is Faraday's Law of Electromagnetic induction, which states that whenever the flux linked with a coil changes an e.m.f is induced, the transformer consists of a laminated iron core(Cold Rolled Grain Oriented Core Lamination) about which are wound two or more sets of windings, voltage is applied to one set of windings, called the primary, which builds up a magnetic flux through the iron. This flux generates a counter e.m.f. in the secondary which limits the current down from the supply.
Makpower transformers are designed and tested as per national & international standards i.e. IS : 2026, IS : 1180, IEC 76, BSI 171, ASA C57 and other relevant IS & IE rules.
Electrolytic grade high conductivity Copper / Aluminium duly insulated with paper / nomex/ glass is used accordingly to application & technical specification of Transformers. For better Short Circuit ability under fault conditions, wound coils are passes, clamped and dried in oven prior to impregnation in Oil. Cooling ducts formed with rigid, high density spacers and horizontal and vertical ducts are provided to save hot spots.
The Core is designed with optimum flux density to minimize core loss and cost. Butt-lap, miter or step-lap-miter construction is chosen based on the application and core-loss requirements.
Laminations are burr free and very thin between 0.23mm and 0.30mm, varying no more than +0.05mm in length for the lowest sound level and excitation currents. Each lamination is covered with a high-resistance, inorganic coating to reduce eddy currents.
The laminations are handled with minimum bending to preserve the low loss properties. The core is clamped in a rigid frame with uniform pressure to reduce mechanical effect on performance.
Makpower uses high electrical grade Kraft Paper & Press Board, as per IS: 1576. The Insulating papers are checked for high dielectric strength, good ageing properties and moisture retardation. Permali wood is also used in top and bottom for mechanical strength.
We use off circuit tap switches for general Transformers, externally operated ON LOAD TAP CHANGER of CTR/OLG make for special transformers and furnace applications, whereas EASUN-MR make, INTANK type OLTC are used in Sub Merged Arc Melting Furnace Transformers, as per customer's technical specification.
All our tanks are fabricated with high grade tested mild steel.The design of the tanks incorporate adequate wall and base thickness so as to withstand the pressure build up in the tank.
Welding is carried out in accordance with strict standards using jigs and fixtures to ensure dimension accuracy. Double weld are provided where oil tightness is required. All oil tight weld are tested to ensure no leakages occurs. Flat gasket of neoprene bonded cork sheets are used for joints and auxiliary fitments.
For ONAN Cooling Pressed sheet steel radiators are used for cooling ensuring that greater surface area is available for high dissipation. The radiators are independently pressure tested and then mounted on the tank.
For ONAF Cooling, Fans are mounted vertically near the radiators for their optimum use.
For OFWF Cooling, Heat Exchangers, oil pumps, oil flow meter, pressure meters, differential pressure gauge is used to suit the losses of transformers at 150% loading condition.
Each transformers tank is tested for leakage by filling them with oil and keeping then under pressure of 0.5 KG/Cm2 or above for several hours. With this test even minute leaks are detected.
All fabricated steel tanks internally & externally cleaned thoroughly of all scales & rust by sand blasting/ shot blasting. A coat of Zinc chromate primer paint is immediately applied to all external surfaces. This anticorrosive paint has rust inhibitive properties and excellent chemical resistance. Two coats of glossy, oil & weather resisting, not fading paint of dark grey, Shade No. 632 of ISS are then applied.
The insulating oil used is of low viscosity with good resistance to oxidation and formation of sludge and acids. Moisture content, dielectric strength etc is determined and certified by conduct relevant testes as per IS-335/ 1993. Generally we use 'transOL' make EHV grade Oil.
Our testing Lab is fully equipped with 100KV High Voltage Test Set, Double Frequency Test Set (Upto 25 MVA, 33 KV), CT's & PT's to check Losses & Impedence, 3 phase Variac for Power supply, Resistance meter, 3 phase Ratio meter in addition to other normal testing instruments.
The list of routine test as per Clause No. 16.1.2 (Part I) of IS : 2026 of 1977 is as follows:
Impulse Test has been conducted on few of our transformers successfully from Central Power Research Institute, Bangalore. Short Circuit test has also been conducted on few transformers at CPRI Bangalore.
