Importance Of Transformer In Field Of Electricity

The electric power now a days has become the necessity of people. Every consumers of any category such as commercial, residential etc needs electric power. So it has become duty of the government to generate electric power and transmit it to the consumers safely and satisfactorily. The development of a state depends upon its industry, its business and other such options which plays a vital role in increasing the per capita income. But parallel to other needs of industry electricity is also a need. No machine can run without it. Similarly, now a days computer has become the part of every business office. It needs too electric power. So if it does not get electric power at appropriate level it will not work and the smoothness business ends.

Different types of consumers needs different voltage levels of electric current. For example a commercial consumer may need a voltage level of 11 kv or 440 v or 6.6 KV while a residential consumer needs power at level of 240 V.

For serving different consumers we cannot give supply to them from different generating stations generating power at different levels. It is not convenient and sometimes impossible. So it becomes a need to generate power at a level and to transmit it to other stations at a higher level and distribute it to consumers at different levels on the voltage level of their need.

So at every step whether voltage level should have to be increased or decreased we need a transformer. So the role of transformer in the transmission and distribution of electric power is very important. The electric power is generated at a level of 12-15 KV and is stepped up to 220 KV or higher levels with the help of step up transformer. At the distribution stations it is stepped down to a lower level 66 KV and send to substations and then further decreasing to 11 KV and 400V it is divided between consumers with the help of stepdown transformer. So transformer has become a necessity due to its important role in power transmission and distribution.

Transformer –In General

Transformer is basically a static device which is defined as a device which can step up or step down the voltage level of A.C. applied to its primary. If the transformer is step up then the voltage on secondary terminals will be high and if the transformer is stepdown then the voltage level on secondary terminals will be low. Any winding can be considered secondary and primary so any transformer may behave as stepup or step down transformer but it is possible only theoretically it is not possible practically on the behalf of insulation reasons. So transformers are wound for different types and for different voltage levels. For stepping up or down a voltage a suitable transformer should be choosed.

As said earlier transformer is a static device. In the construction of it we have a core which is made up of steel sheet stampings these stampings are cut into many steps such as i.e. etc. and are them assembled to have the complete core. On this core the secondary and primary windings are wound. Both the windings are insulated from each other as well as from the core. The no. of turns of primary and secondary coils determines whether it is step up transformer or step down transformer. For stepup transformer secondary no. of turns should be more as compared to primary. For step down transformer these should be less.

Now these windings on the transformer are immersed in the tank which is the mainbody of the transformer. The tank is filled with oil and provided with fins for cooling.

The transformer oil gives two fold results. It cools the windings and insulate the winding from the main tank body. The primary and secondary terminals are made ready with the help of bushings.

Now when the voltage is given to the primary winding of the transformer a flux gets produced, this flux alternating in nature follows a path on the core and get linked to the secondary winding hence a voltage is generated at the secondary winding.

So a transformer is based on FARADAYS LAWS OF ELECTROMAGNETIC

The voltage generated on the secondary depends on the secondary and primary no. of turns. N2/N1 = V2/V1 = I1/I2 = K

Here N is no of turns, V is voltage I is current. 1 and 2 denotes primary & secondary windings respectively. K is called transformation ratio. For the value of K>1 transformer is step-up type and for K<1 it is of step-down type.

So this is the basic working of transformer.

Major Parts Of A Transformer

A transformer in its complete is a assembly of many parts these parts are summurized as:

* MAIN TANK:

It is the outer part of the transformer. The core with windings is fitted in the main tank. The LV and HV terminals are also taken out from the windings through the holes provided in the main tank is required to support the windings and transformer oil.

* COOLING FINS:

Cooling fins are provided with the main tank. These fins are small strips welded together t form a network of small hole pipelies. These are connected from top to bottom with main tank. The hot transformer oils the enters these fins from the top and after cooled by natural air striking the fins enter the main tank again from the bottom. So these fins are provided for the cooling of the transformer oil.

* CONSERVATOR TANK:

Conservator tank is provided on the top of the main tank and it is filled with transformer oil. It is connected directly to the main tank body. The oil filling hole is kept closed after filling the oil in it. A hole is made for the connection of breather with it on the top of the conservator tank. It and main tank are air tighted so that it can breath only from the breather.

* BREATHER:

The breather is provided with the conservator tank. The breather is typically a glass vessel whase top outlet is connected to the conservator ad bottom outlet is free to air. It is connected vertically with the constervator tank. The breather has two chambers top chamber is filled with silicagel and bottom chamber which is of bowl type is filled with transformer oil. The air passes through the breathers. The moisture present in the air is absorbed by the silica gel. The dry air goes inside conservator tank when needed. The presence of moisture change colour of silica gel from blue to pink.

* CORE:

Core provides the main flux path the core is made up of CRGO (cold rolled grain oriented) sheet steel. The CRGO steel sheets are cut into small strips of appropriate size and shape the thickness of the strips is 1-2 mm and width of these is 1 to 2 inch the length of these varies on the basis of rated KVA of the transformer.

These strips are joined in a predescribed form. The limbs in the form are two for single phase transformer and three for three phase transformer.

* WINDINGS:

The primary and secondary windings of transformer are wound on the winding machines. The wires choosen for making coils are generally of copper and aluminium of SWG specified by the Indian Institutes of Standards.

The LT windings are having a small dia and are coiled in such a way to fit the core limb smoothely. The HT winding is of large diameter as compared to the LT winding. Here also the diameter is so choosen that the HT winding fits over the LT winding coils alongwith insulation paper.

* BUSHINGS:

Porceline bushings are provided on both sides of the transformer i.e. on HT and LT side. These bushes are provided on the transformer to insulate the high voltage in touch with the main body of the transformer. The HV cide bushings are large in size as compared to the LV side because of the high voltage on HT Side.

* ARCHING HORNS:

Arching horns are provided at the top and bottom of the HV and LV bushings. These are provided on HV bushings essentially. The purpose of these is to have safe earthing of high voltage without any damage to main transformer body in the case of failure or breakage of the bushing. In such case the top and bottom horns are joins together and so safe earthing is achieved.

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