A transformer is a static device that transfers electric power between two circuits through electromagnetic induction. It increases or decreases voltage while decreasing or increasing current in the secondary circuit. It works on the principle of mutual induction between two coils linked by a common magnetic flux generated by an alternating current in the primary coil. The transformer consists of a core made of laminated silicon steel that carries the magnetic flux, along with a primary coil and secondary coil wound on the core limbs. Energy is transferred from the primary to the secondary coil through the alternating magnetic field without any change in frequency. Core type transformers have a single magnetic circuit with coils wound on both limbs, while shell type transformers have a double magnetic circuit with windings on the central limb.

2. TransformerTransformer -- DefinitionDefinition
Transformer is a static device by means of
which an electric power in one circuit is
transformed to other circuit, without change
in frequency.in frequency.
It can increase or decrease the voltage in a
circuit but with a corresponding decrease or
increase in current.

3. Basic Working PrincipleBasic Working Principle
Mutual Induction between two
circuits linked by a common
magnetic flux.
Faraday’s Law of Electromagnetic
InductionInduction
“whenever a conductor is
placed in a varying magnetic field,
emf is induced in it, which is called
induced emf. If the conductor
circuit are closed, current is also
induced which is called induced
current.”.

4. Transformer RepresentationTransformer Representation

5. Working Principle of TransformerWorking Principle of Transformer
In Transformer, there are two inductive coils,
which are electrically separated and magnetically
coupled.
If one coil is connected to ac source  an
alternating flux is set up in the core  it links
with other coil and produced mutually induced
alternating flux is set up in the core  it links
with other coil and produced mutually induced
emf (Faraday’s Law).
If the second coil is closed, current flows in it –
Thus Energy is transferred.
First Coil  Primary and Second Coil 
Secondary

6. Transformer ConstructionTransformer Construction
• Core :
♦ Carries the flux produced by the winding
♦ It is either square or rectangular shape.
♦ The vertical portion of the core is called Limb
♦ The top and bottom horizontal portion of the core is
called Yoke.
♦ Made of high grade silicon steel laminations
♦ Laminated arrangements reduces eddy current losses.
♦ The laminations are insulated from each other by
using insulation like varnish.

7. Core of a TransformerCore of a Transformer

8. Transformer ConstructionTransformer Construction
• Windings:
Coils used are wound on the limbs and insulated
from each other.
Windings carry the current and produce the
necessary flux
Primary and Secondary coils are insulated from
each other.
Coils are made up of Copper.

9. Windings of a TransformerWindings of a Transformer

10. Conservator : takes up the expansion and
contraction of the oil without allowing it to
come in contact with the ambient air.
Explosion Vent :
A bent pipe
fitted on main
tank, which
Breather :
Extracts the
moisture from
air (using silica
gel crystals) and
does not allow
oil to come in
contact with the
moisture.
tank, which
bursts when
pressure inside
the transformer
becomes
excessive (which
releases the
pressure and
protects the
transformer)

11. Types of Single Phase TransformersTypes of Single Phase Transformers
Core Type Transformer
Shell Type TransformerShell Type Transformer

13. 1. Core Type Transformers1. Core Type Transformers
Single Magnetic Circuit with 2 Limbs – Windings
placed on both the limbs  Winding encircles
the core.
Cylindrical type coils are used with each layers
insulated by paper or mica.insulated by paper or mica.
Low voltage coil is placed near the core and High
voltage coil surrounds the low voltage coil.
Natural cooling is more effective.
Coils can be easily removed by removing the
laminations of the tope yoke, for maintenance

14. 2. Shell Type Transformers2. Shell Type Transformers
Double Magnetic Circuit with 3 Limbs –
Windings placed on central limb  Core
encircles most part of the windings.
Natural Cooling doesn’t existNatural Cooling doesn’t exist
Difficult for maintenance, as for removing any
winding, large laminations to be removed
Preferred for Very High Voltage Transformers.

15. Comparison of Core and Shell TypeComparison of Core and Shell Type
TransformersTransformers