What is transformer, its working principle and types

A transformer is a static device which transform a.c electrical power from one circuit to another at the same frequency but the voltage level is usually changed



 Step up transformer :- Its converts the low voltage (LV) and high current from the primary side of the transformer to the high voltage (HV) and low current value on the secondary side.

Step down transformer :- Its converts the high voltage (HV) and low current from the primary side of the transformer to the low voltage (LV) and high current value on the secondary side.


Working Principle

 Principle:-It works on the electromagnetic induction principle

Working:- When the two independent coils are wound on the rectangular shape of laminated cores and an alternating voltage is applied to winding No.1 which is known as primary winding an alternating flux is produced in the magnetic circuit. This alternating flux produced in the magnetic circuit, links with another windings No.2 Which is known as secondary winding due to mutual induction with the result another voltage is induced in the secondary winding which is used for the circuit.




1. Tank: -The assembly of case and winding is put into a mild-steel tank winding is put into a mild-steel tank This tank is filled with insulating oil which is also called as transformer oil. The working of the tank is to protest core-winding assembly, cooling it through transformer oil.

2.  Tank cover: – The tank cover is also made with a mild steek sheet, where the bushing terminal, Conservator, Buchholz relay and the thermometer are mounted.

3.  Conservator tank:- It is small cylindrical type construction made with the main sheet it is connected with the main oil tank through the pipeline and also connected with a breather. The main working of the conservator tank is.

       It always fulfill the main oil tank with transformer oil.

       It stored extra oil for main oil, so it also called extra oil storage tank

➢ When a load of transformer alternates that is When the electric load  is increasing and decreasing Due to this the volume of transformer oil starts increasing and decreasing

   It protects the transformer oil from oxidation

4. Temperature gauge: – It is also a protecting device fitted to indicate the temperature of transformer oil.


5. Explosion vent: – It is also a safety device which protects the transformer tank from the gases induced by any type of short circuit.

6. Pipes:-These are fitted for cooling the transformer oil. The hot oil circulates through these pipes where it because cool due to the air touching.

7. Tap changer:- It is a type of selector switch, which is connected with the high voltage winding of the transformer with the help of this tap changer we control the  output voltage by converting the number of turns from this tap changer, we change 5% output voltage (+and -). This tap changer is mounted vertically with a transformer tank wall.

8.  Buchholz Relay or Gas Relay: – This relay is a type of mechanical cum electrical relay, which works a gas pressure. so, it is also called a gas relay The Buchholz Relay is connected between conservator and tank by means of a pipe. This relay works on the internal fault of the transformer.

Under normal fault condition, the Buchholz relay switch on the alarm circuit and provide fault information to the operator through the loud horn.

Under abnormal fault condition, The Buchholz Relay switched-on trip circuit and cut-off the supply voltage and thus the Buchholz relay protects it from faults

9. Breather:  Silica  gel  Breather  is  a  cylindrical  type container which is fitted to the conservator tank through a pipe line which is totally filled with silica gel. It is used for absorbing moisture present in surrounding air during breathing action  due the expansion and construction of transformer oil.