Group no. – 13
First year bridge course
RISHI MERVANA 14BEEEG025
NISARG AMIN 14BEEEG012
URVISH PATEL 14BEEEM032
DARSHAN MAHAVAR 14BEEEG029
Guide Teacher :- S.M.Pujara
The alternating current has
several advantages over direct
current is that,
Alternating Current can be easily
transferable from low to high
Alternating voltage can be raised
or lowered as per requirement by a
static device called
What is a transformer?
A static piece of apparatus by means of
which an electrical power is transferred
from one alternating current circuit to
another electrical circuit
There is no electrical contact between
The desire change in voltage or current,
without any change in frequency.
Symbolically the transformer
Structure of Transformer:
The transformer consists of 2 inductive coils,
they are electrically separated but linked
through a common magnetic circuit. They have
high mutual induction
One of them is connected to a source of
alternating voltage. This coil in which electrical
energy is fed with the help of source called
The other winding is connected to a load. The
electrical energy is transformed to this winding
drawn out to the load. This winding is called
The primary & secondary coil wound on
a ferromagnetic metal core. The
function of the core is to transfer
the changing magnetic flux from the
primary coil to secondary coil.
The no. of turns plays an important
role in the function of transformer.
The transformer works in the principal of
“ The principle of mutual induction states
that when 2 coils are inductively coupled
and if the current in coil change uniformly
then the e.m.f induced in the other coil.
This e.m.f can drive a current when a
closed path is provided to it.”
When an Alternating current flows in
Primary coil, a changing magnetic flux is
generated around the primary coil.
The changing magnetic flux is transferred to
the secondary coil through the iron core.
The changing magnetic flux is cut by the
secondary coil, hence induces e.m.f. in the
Now if load is connected to a secondary
winding, this e.m.f. drives a current through it.
The magnitude of the output voltage can be
controlled by the ratio of the no. of primary
coil & secondary coil.
“The frequency of mutually induced e.m.f as
same that of the alternating source which
supplying energy to the primary winding”
There are 2 basics of transformer contraction.
1. Magnetic Core
2. Windings or coils
The core of transformer either square or rectangular
type in size
Core is made of laminations. Because of laminated core
type constructions, eddy current losses get minimize.
Generally high grade silicon steel laminations (0.3 to 0.5
mm) are used.
These lamination are insulated from each other by using
insulation like varnish or thick paper.
Conducting material is used in the windings of
The coils used are wound on the limbs and
insulated from each other.
The 2 different windings are wounds on 2
different limbs i.e. primary on 1 limbs while
secondary on other limb in the basic
The leakage flux increase which affects the
performance and efficiency of transformer.
To reduce the leakage flux it is necessary that
the windings should be very close to each other
to have high mutual induction.
Core type Construction:
In the core type 1 magnetic circuit &
cylindrical coils are used.
These coils are mechanically strong.
Normally L & T shaped laminations are
Commonly primary winding wound on 1 limb
while secondary on the other but
performance will be reduce.
To get high performance it is necessary
that the 2 windings should be very close to
Shell type construction:
In the shell type 2 magnetic circuit are used.
The windings is wound on central limbs.
For the shell type each high voltage winding lie
between 2 low voltage portion sandwiching the high
Sub-division of windings reduces the leakage flux.
All the portions are insulated by paper.
Greater the no. of sub-divisions lesser the
This type of construction is used for high voltages.
Losses In Transformer:
In transformer, there exists 2 types of
1. Core losses
2. Copper losses
Core losses: It has also 2 types of losses.
1. Hysteresis loss: During magnetization and
demagnetization, due to hysteresis effect some
energy losses in the core called hysteresis.
2. Eddy current loss: The leakage magnetic flux
generates the e.m.f. in the core produces
current is called eddy current loss.
The copper losses is due to power wasted
in the form of I2r due to resistance of
primary and secondary. The magnitude of
copper losses depend upon the current
flowing through these coils.
“The iron losses depend on the supply voltage
while the copper losses depend upon the
current. The losses are not dependent on
the phase angle between the voltage and
Types of transformer:
Step up transformer
No. of secondary
windings are greater
than the no. of primary
It converts low
alternate voltage to
high alternate voltage.
This type of
transformer is called
step up transformer.
Step down transformer
No. of primary windings
are greater than the no.
of secondary windings
It converts high
alternate voltage to low
This type of
transformer is called
step down transformer.
Ideal V/S Practice
A transformer is said to be ideal if it satisfies
the following properties, but no transformer is
ideal in practice.
It has no losses
Windings resistance are zero
There is no flux leakage
Small current is required to produce the
While the practical transformer has winding
resistance, some leakage flux and has little bit
Can a transformer step up or step down
the DC current or voltage?
The DC supply cannot be used for
Because the transformer works on the
principle of mutual induction, for which the
current in the coil changes uniformly. If
DC supply is applied the current does not
change uniformly due to constant supply
and transformer will not work.
“The DC supply may cause the transformer
to damage permanently”
Applications & Uses:
The transformer is used in Television and
The transformer(ballast transformer) are also
installed in fluorescent tube lights.
The transmission & distribution of alternating
power is possible by transformer.
Simple camera flash uses fly back transformer.
Signals and audio transformer are used couple
“Today transformer has become an essential part
of electronics engineering”