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CONSTRUCTION OF TRANSFORMER
This paper describes the principle and construction of transformer in brief. All parts in transformer are explained like Bushings, Conservator tank, Breather, etc.., Types of transformers.
Transformer is a device which is used to transform electrical energy from one circuit another circuit without any change in frequency. This process goes through inductively coupled circuits which are the coils of the transformer. It consists of two coils they are primary and secondary coils.
Principle of Transformer:
The transformer works on the principle of ‘MUTUAL INDUCTION’. An alternating flux in the primary coil will create an alternating flux in the transformer core, which is linked with the other coil which produces a mutually induced emf according to faraday’s laws of electromagnetic induction.
If the secondary circuit is connected to the load then the electrical current passes through the secondary winding which is transferred from primary coil. To step up the voltage the secondary winding turns are greater than the primary winding turns and for the step down the primary winding turns should be more than the secondary winding turns.
Construction of Transformer:
The transformer is very simple in construction and it consists of magnetic circuit linking with two windings. The main parts of transformer are
1. Core construction.
4. Transformer tank.
5. Conservator tank.
7. Buchholz relay.
. Core of the transformer is either in square or rectangular in size. It is further divided into two parts. The vertical position of the core is limbs and horizontal position of the core is yoke of the core. Core is made up of laminations to reduce the eddy current losses get minimized. This lamination is insulated by using insulations line varnish or thick paper. Paper insulation is used for low voltage transformer and varnish is used for high voltage transformer.
Conducting material is used in the windings of the transformer. Usually the windings are in concentrically to minimize the flux leakages. There are two types of windings. The coils are wound on the limbs and are insulated from each other in the basic transformer the two windings wound on the two different limbs. Due to this leakage flux increases which affects the transformer efficiency or performance so it should be necessary that the windings should be very close to each other to increase the mutual inductance and stray capacitance to improve the high frequency response.
Such cylindrical coils are used in core type transformers and sandwich coils are very commonly used in shell type transformer here each high voltage winding lies between two low voltage windings such subdivisions of windings into small portions reduce the flux leakages.
Small capacity tanks are fabricated from sheet steel while larger ones are assembled with cast aluminium. For cooling purpose the tank is welded with cooling tubes. These are some types of transformer tanks.
Conservator tank consists of oil level which depends on the operation of the transformer. The oil expands in summer with the increase in load and the oil contracts with decrease of the load. Conservator is a small auxiliary oil tank that may be mounted above the transformer and connected to the main tank by a pipe.
Its main function is to keep the main tank of the transformer completely filled with the oil in all circumstances. When the oil in the tank contracts then the conservator gives the oil to maintain the oil level in the tank. When the oil in the tank expands then the conservator takes the oil.