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2. What is Transformer ??
A transformer is a
static device which
able to transfer the
power from one circuit
to another circuit
without altering the
frequency .

3. Principle Of Operation
Transformer works on the
principle of mutual induction
of two coils. When current in
the primary coil is changed
the flux linked to the
secondary coil also changes.
Consequently an EMF is
induced in the secondary coil.

4. Primary and Secondary Windings
A two-winding transformer consists of two windings
interlinked by a mutual magnetic field.
– Primary winding – energized by connecting it to an
input source
– Secondary winding – winding to which an electrical
load is connected and from which output energy is
drawn.

5. Working….
When the primary winding is connected to
an ac supply mains, current flows
through it. winding produces an
alternating flux in the core. Since this
flux is alternating and links with the
secondary winding also, so induces an
emf in the secondary winding. The
frequency of induced emf in secondary
winding is the same as that of the flux or
that of the supply voltage. The induced
emf in the secondary winding enables it
to deliver current to an external load
connected across it. Thus the energy is
transformed from primary winding to the
secondary winding by means of electro-
magnetic induction without any change
in frequency.

6. Construction of Transformer
Mainly Transformers have
two types of
construction….
 CORE type construction
 SHELL type construction

8. Core type Transformer
In the Core type the
primary and
secondary windings
are placed on each
side of the core.
The core type has
two limbs

9. Shell type Transformer
In Shell type
transformers the LV
and HV windings
are sandwiched
between each other.
shell type has three
limbs.

10. Ideal Transformers
No iron and copper losses
No leakage fluxes
A core of infinite magnetic
permeability
Flux is confined to the core
The windings have zero resistance
An ideal transformer is a lossless device with an input
winding and an output winding. It has the following
properties:

11. Equivalent Circuit of an Ideal
Transformer at No Load

12. Types of Transformer
Step UP Transformer :
A transformer in which Ns>Np is called a step up
transformer. A step up transformer is a transformer
which converts low alternate voltage to high
alternate voltage.
Step DOWN Transformer :
A transformer in which Np>Ns is called a step
down transformer. A step down transformer is a
transformer which converts high alternate voltage
to low alternate voltage.

13. A wide variety of transformer designs are
used for different applications.
Auto-transformer
Poly-phase transformer
Leakage transformer
Resonant transformer
Instrument transformers

14. AUTO-TRANSFORMERS
Autotransformer is a one winding transformer in
which a part of the winding is common to both HV
and LV sides.

15. POLY-PHASE TRANSFORMER
• Three separate single phase
transformers are suitably
connected for 3 phase
operation.
• A single three phase
transformer in which the
cores and windings for all
the three phases are
combined in a single
structure.

16. Losses In Transformers….
The losses that occur in transformers have to be accounted for in any accurate
model of transformer behavior.
1. Copper (I2R) losses. Copper losses are the resistive heating losses in the
primary and secondary windings of the transformer. They are proportional to
the square of the current in the windings.
2. Eddy current losses. Eddy current losses are resistive heating losses in the core
of the transformer. They are proportional to the square of the voltage applied to
the transformer.
3. Hysteresis losses. Hysteresis losses are associated with the rearrangement of the
magnetic domains in the core during each half-cycle. They are a complex,
nonlinear function of the voltage applied to the transformer.
4. Leakage flux. The fluxes which escape the core and pass through only one of
the transformer windings are leakage fluxes. These escaped fluxes produce a
self-inductance in the primary and secondary coils, and the effects of this
inductance must be accounted for.

17. Efficiency of a Transformer
Transformer efficiency may be defined as the ratio
between Output and Input. Efficiency = Output/Input
• Efficiency = η= Output / Input
• Efficiency = η= Output / (Output + Losses) …….… (As
Input = Output +Losses)
• Efficiency = η= Output / (Output +Cupper Losses +
Iron Losses)
You may also find the Efficiency by the following formula
• Efficiency = η = (Input – Losses) / Input …….… (As
Output = Input – Losses)
Taking LCM
• Efficiency = η = 1 – (Losses /Input)

18. What is Voltage Regulation ?
The voltage regulation is the change in terminal voltage of the secondary from
no load to full load voltage.