Basic Functions Of Transformer & Types | Electrical Engineering - Electrical4u

 Transformers 

A transformers transfers , Electrical energy from one circuit to another through inductively coupled conductors . it is widely used to change the voltage and current and either be increase or decrease as required .

Transformers Required little care and maintenance because of their simple, rugged and durable construction . The Efficiency of transformer is very high because there are no moving parts.

Working principle of Transformers 

A Transformer is static device by means of which electrical power in one circuit is transformed to another circuit without a change of frequency .

It operates on the principle of mutual inductance between two inductively coupled coil. These inductive coils are electrically separated but magnetically linked through a path of low reluctance. it consist of two windings . i.e Primary winding and secondary winding . Primary winding is energised by a sinusoidal voltage . Secondary winding Feeds The Load. 

Most of these fluxes are linked with secondary windings in which they produces mutually induced e.m.f. This induced e.m.f drives current through the load connected to winding . Energy is transferred from the primary windings to the secondary winding through the magnetic field. 

Construction of transformers 

The Construction of transformer is very simple , rugged and durable in construction and consist of magnetic circuit linking with two windings as primary and secondary windings. 

The Main Components of  a Transformers 

1. Terminal Bushings 

2. Buchholz Relay 

3. Transformer Tank 

4. Breather 

5. Conservator Tank Oil Level

6. Core 

Core

Transformers core is constructed from thin sheet of high grade silicon steel with 4%  Silicon . This Sheets are Laminated and are coated with an oxide layer to reduce the iron losses . The purpose of core is to provide a magnetic path of low reluctance between the two windings. 

Winding 

A transformer has two windings . This Windings which receives the electrical energy is called the primary winding and the winding which delivers the electrical energy is known secondary winding. Winding Is Generally made of high grade copper. 

Conservator

Oil immersed transformers are normally equipped with conservator  . it consist of an airtight cylindrical metal drum supported horizontally on transformer lid. It should be provided with a detachable bottom or an access hole , so that the conservator can be painted from inside or cleaned from oil sludge .

Conservator is used to take up contraction and expansion of oil without allowing it to come in contact with outside air. 

Buchholz Relay

Buchholz Relay is used in transformer as a protective device to detect internal faults that may occur in the transformer . It is one of the most important Component of the transformer .it is install in oil immersed transformer 

This Relay is Also Known As 

• Pre - Fault relay 

• Gas actuated relay

It is used to protect the transformer having rating more than 500kVA . This Relay also detect losses of oil caused by leaks as well as defects such as broken conductors and corroded or otherwise bad connections . it is installed in between Transformer Tank And Conservator Tank 

Advantage of Buchholz Relay

1.  It detects the incipient faults at a stage much earlier than in any other from of protection
2. It is the simplest form of transformer Protection 

Disadvantages of Buchholz Relay

1. Use of Buchholz relay is limited to oil immersed transformer which is provided with conservator
2. It cannot be used on the  transformers having rating less than 500kVA
3. It can detect only faults below oil level in the transformer 

Limitations Of Buchholz Relay 

This relay is slow . it has a minimum operating range of 0.1 second and an average operating range of 0.2 seconds . 

Terminal Bushing

The Terminal Connections of the winding are taken to the insulator bushings mounted on the transformer tank top . the bushing consist of a current carrying part in the form of the conduction rod and a porcelain cylinder installed in the hole of cover and used to isolated to current carrying part. Ordinary porcelain isolators can be used upto a voltage rating of 33kV . When the voltage is High exceeds 33kV , Condenser bushing or oil filled terminals bushing are generally used.