The document provides an extensive overview of transformers, detailing their definition, construction, working principles, types, and applications. It explains how transformers operate on the principle of mutual induction to change voltage and current levels without changing frequency, with descriptions of step-up and step-down transformers. Additionally, it covers various transformer classifications based on phase, core type, cooling systems, and specialized designs for maritime applications.

1. CONTENT
 What is transformer
 Structure and working principle
 Construction of transformer
 Losses in transformer
 Ideal v/s practical transformer
 Uses and application of transformer

2. introduction
 A transformer is a device that changes ac electric power at one
voltage level to ac electric power at another voltage level
through the action of a magnetic field.
 There are two or more stationary electric circuits that are
coupled magnetically.
 It involves interchange of electric energy between two or more
electric systems
 Transformers provide much needed capability of changing the
voltage and current levels easily.
 They are used to step-up generator voltage to an appropriate
voltage level for power transfer.
 Stepping down the transmission voltage at various levels for
distribution and power utilization.

3. What is transformer
 A transformer is 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 them
 The desire change in voltage or current without any change in
frequency
 Symbolically the transformer denoted as
NOTE :
It works on the principle of mutual induction

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

6. Basic Working Principle
Mutual Induction between two
circuits linked by a common
magnetic flux.
Faraday’s Law of Electromagnetic
Induction
“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.”.

7. Transformer Representation

8. Working 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 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

9. TRANSFORMER
• A transformer is a static device.
• The word ‘transformer’ comes form the word ‘transform’.
• Transformer is not an energy conversion device, but it is device that changes
electrical power at one voltage level into electrical power at another voltage
level through the action of magnetic field but with a proportional increase or
decrease in the current ratings., without a change in frequency.
• It can be either to step-up or step down.

11. TYPES OF TRANSFORMER
STEP UP TRANSFORMER:
A transformer in which voltage across
secondary is greater than primary voltage
is called a step-up transformer (shown in
figure)
In this type of transformer, Number of
turns in secondary coil is greater than that
in Primary coil, so this creates greater
voltage across secondary coil to get more
output voltage than given through primary
coil.

12. TYPES OF TRANSFORMER
STEP DOWN TRANSFORMER:
•A transformer in which voltage across
secondary is lesser than primary voltage is
called a step-down transformer (shown in
figure)
•In this type of transformer, Number of
turns in secondary coil is lesser than that in
Primary coil, so this creates lesser voltage
across secondary coil, so we get low
output voltage than given through primary
coil.

13. The transformer works in the principle of mutual induction
“The principle of mutual induction states that when the two
coils are inductively coupled and if the current in coil change
uniformly then the e.m.f. induced in the other coils. This e.m.f
can drive a current when a closed path is provide to it.”
When the alternating current flows in the primary coils, a changing magnetic
flux is generatedaround 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 an e.m.f
in the secondary coil
WORKING

14. Structure of transformer
 The transformer two inductive coils ,these are electrical
separated but linked through a common magnetic current
circuit
 These two coils have a high mutual induction
 One of the two coils is connected of alternating voltage .this
coil in which electrical energy is fed with the help of source
called primary winding (P) shown in fig.
 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 secondary winding(S) shown in fig.

15.  The primary and 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 the secondary coil
 The primary has N1 no of turns and the secondary has N2 no of
turns the of turns plays major important role in the function of
transformer

16. Working principle
 The transformer works in the principle of mutual induction
 When the alternating current flows in the primary coils, 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 an e.m.f in the secondary coil
“The principle of mutual induction states that when the two coils are
inductively coupled and if the current in coil change uniformly then the
e.m.f. induced in the other coils. This e.m.f can drive a current when a
closed path is provide to it.”

17.  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 and secondary coil
The frequency of mutually induced e.m.f as same
that of the alternating source which supplying to the
primary winding b

19. Constructionof transformer
 These are two basic of transformer construction
 Magnetic core
 Windings or coils
 Magnetic core
 The core of transformer either square or rectangular type in
size
 It is further divided into two parts vertical and horizontal
 The vertical portion on which coils are wounds called limb
while horizontal portion is called yoke. these parts are
 Core is made of laminated core type constructions, eddy
current losses get minimize.
 Generally high grade silicon steel laminations (0.3 to 0.5mm)
are used

20. winding
 Conducting material is used in the winding of the transformer
 The coils are used are wound on the limbs and insulated from
each other
 The two different windings are wounds on two different limbs
 The leakage flux increases 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

21. 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 and secondary coil
The frequency of mutually induced e.m.f as same that of
the alternating source which supplying to the primary
winding b

22.  For the simple construction of a transformer, you must need two coils having
mutual inductance and a laminated steel core. The two coils are insulated
from each other and from the steel core. The device will also need some
suitable container for the assembled core and windings, a medium with
which the core and its windings from its container can be insulated.
 In order to insulate and to bring out the terminals of the winding from the
tank, apt bushings that are made from either porcelain or capacitor type must
be used.
 In all transformers that are used commercially, the core is made out of
transformer sheet steel laminations assembled to provide a continuous
magnetic path with minimum of air-gap included. The steel should have high
permeability and low hysteresis loss. For this to happen, the steel should be
made of high silicon content and must also be heat treated. By effectively
laminating the core, the eddy-current losses can be reduced. The lamination
can be done with the help of a light coat of core plate varnish or lay an oxide
layer on the surface. For a frequency of 50 Hertz, the thickness of the
lamination varies from 0.35mm to 0.5mm for a frequency of 25 Hertz.

23. Transformer 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.

24. Core of a Transformer

25. Transformer 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.

26. Windings of a Transformer

27. 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
air (using
Breather :
Extracts the
moisture from
silica
gel crystals) and
does not allow
oil to come in
contact with the
moisture.
fitted
tank,
bursts
pressure
pipe
on main
which
when
inside
the transformer
becomes
excessive (which
releases the
pressure and
protects the
transformer)

28. Classification of Transformer
• As per phase
1. single phase
2. Three phase
• As per core
1. Core type
2. Shell type
• As per cooling system
1. Self-cooled
2. Air cooled
3. Oil cooled

30. Three phase transformer
Normally , when three-phase is required, a single enclosure with three
primary and three secondary windings wound on a common core is all that
is required. However three single-phase transformers with the same rating
can be connected to form a three-phase bank. Since each single-phase
transformer has a primary and a secondary winding, then 3 single-phase
transformers will have the required 3 primary and 3 secondary windings and
can be connected in the field either Delta-Delta or Delta-Wye to
achieve the required three-phased transformer bank

45. - 30 degree phase difference
between the Primary and
Secondary.
-The Delta-to-Wye connection is
the most popular connection
used to supply low-voltage
distribution systems.
-The Wye secondary allows for
supply for both single-phase and
three-phase loads.
-The Wye is grounded at the
neutral point to limit the available
voltage to ground during a
ground fault on any
lineconductor.
Note: In the past, many low-
voltage, three-phase loads were
supplied by an ungrounded Delta
secondary. In those systems,
induced transient over-voltages
often caused insulation to break
down. Today, new installations
are made much safer through the
use of the grounded, wye-
connected secondary.

46. Types of Single Phase
Transformers
Core Type Transformer
Shell Type Transformer

48. 1. 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.
 Low voltage coil is placed near the core and High
voltagecoil surrounds the low voltagecoil.
 Natural cooling is more effective.
 Coils can be easily removed by removing the
laminations of the tope yoke, for maintenance

49. Core type construction
 In this one magnetic circuit and cylindrical coils are used
 Normally L and T shaped laminations are used
 Commonly primary winding would on one limb while
secondary on the other but performance will be reduce
 To get high performance it is necessary that other the two
winding should be very close to each other

51. Transformer classified
as per core
 CORE TYPE TRANSFORMER:-
In core-type transformer, the windings are given to a
considerable part of the core. The coils used for this transformer are form-wound and are of
cylindrical type. Such a type of transformer can be applicable for small sized and large sized
transformers. In the small sized type, the core will be rectangular in shape and the coils used are
cylindrical. The figure below shows the large sized type. You can see that the round or cylindrical
coils are wound in such a way as to fit over a cruciform core section. In the case of circular
cylindrical coils, they have a fair advantage of having good mechanical strength. The cylindrical
coils will have different layers and each layer will be insulated from the other with the help of
materials like paper, cloth, macerate board and so on. The general arrangement of the core-type
transformer with respect to the core is shown below. Both low-voltage (LV) and high voltage (HV)
windings are shown.

52. The low voltage windings are placed nearer to the core as it is
the easiest to insulate. The effective core area of the
transformer can be reduced with the use of laminations and
insulation

53. 2. 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
Difficult for maintenance, as for removing any
winding, large laminations to be removed
Preferred for Very High Voltage Transformers.

54. Shell type construction
 In this type two magnetic circuit are used
 The winding is wound on central limbs
 For the cell type each high voltage winding lie between two
voltage portion sandwiching the high voltage winding
 Sub division of windings reduces the leakage flux
 Greater the number of sub division lesser the reactance
 This type of construction is used for high voltage

55. 2. Shell-Type Transformer
In shell-type transformers the core surrounds a considerable portion of
the windings. The comparison is shown in the figure below.
The coils are form-wound but are multi layer disc type usually wound in the form of pancakes.
Paper is used to insulate the different layers of the multi-layer discs. The whole winding consists
of discs stacked with insulation spaces between the coils. These insulation spaces form the
horizontal cooling and insulating ducts. Such a transformer may have the shape of a simple
rectangle or may also have a distributed form. Both designs are shown in the figure below:

57. Comparison of Core and Shell
Type Transformers

58. A strong rigid mechanical bracing must be given to the cores and coils of the transformers. This will
help in minimizing the movement of the device and also prevents the device from getting any
insulation damage. A transformer with good bracing will not produce any humming noise during its
working and will also reduce vibration.
A special housing platform must be provided for transformers. Usually, the device is placed in tightly-
fitted sheet-metal tanks filled with special insulating oil. This oil is needed to circulate through the
device and cool the coils. It is also responsible for providing the additional insulation for the device
when it is left in the air.

60. CLASSIFICATION ON THE BASIS OF
COOLING EMPLOYED
 1. Oil Filled Self-Cooled Type
 Oil filled self cooled type uses small and medium-sized distribution transformers. The assembled
windings and core of such transformers are mounted in a welded, oil-tight steel tanks provided with a
steel cover. The tank is filled with purified, high quality insulating oil as soon as the core is put back at
its proper place. The oil helps in transferring the heat from the core and the windings to the case from
where it is radiated out to the surroundings. For smaller sized transformers the tanks are usually smooth
surfaced, but for large size transformers a greater heat radiation area is needed, and that too without
disturbing the cubical capacity of the tank. This is achieved by frequently corrugating the cases. Still
larger sizes are provided with radiation or pipes.
 2. Oil Filled Water Cooled Type
 This type is used for much more economic construction of large transformers, as the above told self
cooled method is very expensive. The same method is used here as well- the windings and the core are
immersed in the oil. The only difference is that a cooling coil is mounted near the surface of the oil,
through which cold water keeps circulating. This water carries the heat from the device. This design is
usually implemented on transformers that are used in high voltage transmission lines. The biggest
advantage of such a design is that such transformers do not require housing other than their own. This
reduces the costs by a huge amount. Another advantage is that the maintenance and inspection of this
type is only needed once or twice in a year.
 3. Air Blast Type
 This type is used for transformers that use voltages below 25,000 volts. The transformer is housed in a
thin sheet metal box open at both ends through which air is blown from the bottom to the top.

62. Basically a transformer consists of
• ¥ primary winding
• ¥ secondary winding
• ¥ core
• ¥ tank
• ¥ bushings
• ¥ oil conservator

63. MARINE TRANSFORMER
Shipboard transformers have specific characteristics and requirements tailored for marine and maritime
applications. Here are some of the key features of shipboard transformers:
1. Corrosion Resistance: Shipboard transformers must exhibit excellent corrosion resistance, as they
typically operate in the moist and corrosive marine environment. This necessitates the use of
corrosion-resistant materials, such as stainless steel, for both external and internal components.
2. Pressure Adaptability: Shipboard transformers need to withstand the pressure of seawater. As a
result, their enclosures must be sealed to prevent water ingress and endure varying pressures from
low to high.
3. Vibration Resistance: Ships experience motion, pitching, and vibrations at sea. Shipboard
transformers must be designed to withstand these conditions and maintain stability under adverse
circumstances.
4. Compact Design: Space on ships is often limited, so shipboard transformers are designed to be
compact, minimizing their footprint.
5. High Efficiency: To reduce fuel consumption and enhance overall energy efficiency on ships,
shipboard transformers must be highly efficient, minimizing energy losses during power
transmission.
6. Isolation and Protection: Shipboard transformers must provide effective electrical isolation to
prevent interference with other systems. They also require appropriate overload and short-circuit
protection mechanisms to prevent failures.
7. Multi-Voltage Adaptability: Ships typically require power at various voltage levels. Shipboard
transformers often have multiple windings to accommodate different voltage requirements.
8. Maritime Certification: Shipboard transformers must conform to international maritime
certification standards to ensure their legitimate use on vessels.
In summary, shipboard transformers are required to provide reliable power conversion and distribution in
the challenging marine environment while adhering to maritime regulations and safety

72. Ideal transformer
 An ideal transformer is a transformer which has no loses, i.e. it’s
winding has no ohmic resistance, no magnetic leakage, and therefore
no I2 R and core loses.
 However, it is impossible to realize such a transformer in practice.
 Yet, the approximate characteristic of ideal transformer will be used in
characterized the practical transformer.
V1 V2
N1 : N2
E1 E2
I1 I2
V1 – Primary Voltage
V2 – Secondary Voltage
E1 – Primary induced Voltage
E2 – secondary induced Voltage
N1:N2 – Transformer ratio

73. Transformer Efficiency
 To check the performance of the device, by comparing the
output with respect to the input.
 The higher the efficiency, the better the system.
%
100
cos
cos
%
100
%
100
,
2
2
2
2









cu
c
losses
out
out
P
P
I
V
I
V
P
P
P
Power
Input
Power
Output
Efficiency



%
100
cos
cos
%
100
cos
cos
2
)
(
)
(








cu
c
n
load
cu
c
load
full
P
n
P
nVA
nVA
P
P
VA
VA






Where, if ½ load, hence n = ½ ,
¼ load, n= ¼ ,
90% of full load, n =0.9
Where Pcu = Psc
Pc = Poc

74. Transformer Losses
 Generally, there are two types of losses;
i. Iron losses :- occur in core parameters
ii. Copper losses :- occur in winding resistance
i. Iron Losses
ii Copper Losses
circuit
open
c
c
c
iron P
R
I
P
P 

 2
)
(
02
2
2
01
2
1
2
2
2
1
2
1
)
(
)
(
,
)
(
)
(
R
I
R
I
P
referred
if
or
P
R
I
R
I
P
P
cu
circuit
short
cu
copper







76. Losses in transformer
 Copper losses :
It is due to power wasted in the form of I2Rdue 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 depend
on the current .the losses are not dependent on the phase angle between
current and voltage .hence the rating of the transformer is expressed as
a product o f voltage and current called VA rating of transformer. It is
not expressed in watts or kilowatts. Most of the timer, is rating is
expressed in KVA.

77. Hysteresis loss :
During magnetization and demagnetization ,due to hysteresis
effect some energy losses in the core called hysteresis loss
Eddy current loss :
The leakage magnetic flux generates the E.M.F in the core
produces current is called of eddy current loss.

78. Ideal V/S practical transformer
 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 magnetic field
While the practical transformer has windings resistance , some
leakage flux and has lit bit losses

79. Application and uses
 The transformer used in television and photocopy machines
 The transmission and distribution of alternating power is
possible by transformer
 Simple camera flash uses fly back transformer
 Signal and audio transformer are used couple in amplifier
Todays transformer is become an essential part of
electrical engineering

80.  EDDY CURRENTS
 By Changing Flux through a solid
conductor, induced currents are set up
within the body of a conductor in a
direction perpendicular to the flux
which are eddy currents.
 Since our iron core is ferromagnetic
material, so it allows these currents to
pass through the whole body of
conductor causing heating of core of
conductor.
 This is a power loss in transformer(
shown as in figure 1 ), to reduce this
the core should be made of lamination
sheets which stop the flow of eddy
currents (shown as in figure 2).

81.  HYSTERESIS LOSS
 The energy spent in magnetisation and
demagnetisation of the core of
transformer is called hysteresis loss.
 This loss in energy is expressed by
using B-H(magnetic flux density B
and flux density H) curve for a
specific ferromagnetic material.
 For reducing this loss, we should use
such a soft material for core whose
hysteresis loop is very small.
 The hysteresis loops of both hard and
soft magnetic materials are shown
respectively, which shows that soft
magnetic materials have small
hysteresis loss of energy.

82. AC TRANSFORMER AND RECTIFIER UNIT

99. BYE