Transformer: Introduction, development, uses and calculations. This slide was made as a class presentation.

2. TRANSFORMER
PRESENTED BY :
1. Md. Ragib Noor ID- 021 151 093
2. Saima Afrose Khan ID- 021 143 033
3. Abdullah Al Mojib ID- 021 141 064
4. Khan Tarikul Islam Taru ID- 021 143 050

3. HISTORY
• In 1831, Micheal faraday and Joseph Henry independently
gave the principle of transformer in the form of
electromagnetic induction showing:
where ε is the magnitude of the EMF in volts and ΦB is
the magnetic flux through the circuit in webers
• The first type of transformer to see wide use was the induction
coil, invented by Rev. Nicholas Callan of Maynooth College,
Ireland in 1836.
• . Between the 1830s and the 1870s, efforts to build better
induction coils, mostly by trial and error, slowly revealed the
basic principles of transformers.

5. Transformer:Definition
A TRANSFORMER is a device that transfers
electrical energy from one circuit to another by
electromagnetic induction (transformer action).
or
A transformer is an electrical device that steps up
or steps down the AC voltage without a change in
frequency.

6. Transformer equivalent circuit

8. CONSTRUCTION (Basic)
• It consists of an iron core on which two separate coils of
insulated copper wire are wound.
• The Coil to which A.C power voltage is supplied is Primary
Coil.
• The Coil to which this power is delievered to circuit is
Secondary Coil.
• The Secondary Coil has a load resistance connected to safe
transformer from being heating up.
• These coils have no electrically linked as they have
magnetical links.
• Construction of a simple transformer can be seen from
figure:

9. Working Principle :
• The main principle of operation of a transformer is mutual
inductance between two circuits which is linked by a
common magnetic flux. A basic transformer consists of two
coils that are electrically separate and inductive, but are
magnetically linked through a path of reluctance. The
working principle of the transformer can be understood
from the figure below

10. Continue :
• In short, a transformer carries the operations shown
below:
• Transfer of electric power from one circuit to another.
• Transfer of electric power without any change in frequency.
• Transfer with the principle of electromagnetic induction.
• The two electrical circuits are linked by mutual induction.

11. 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

12. 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.

13. 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.

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

15. 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

16. 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.

17. 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.

18. CLASSIFICATION ON THE BASIS OF
COOLING EMPLOYED :
• 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.

19. CLASSIFICATION ON THE BASIS OF
COOLING EMPLOYED :
• 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.

20. Transformer classified as per phase :

21. Transformer classified as per phase :
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

22. Also ,A wide variety of transformer
designs are used for different
applications:
Auto-transformer
Poly-phase transormer
Leakage transformer
Resonant transformer
Instrument transformers

23. Calculation

29. 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,
22
22







cuc
lossesout
out
PPIV
IV
PP
P
PowerInput
PowerOutput
Efficiency



%100
cos
cos
%100
cos
cos
2)(
)(






cuc
nload
cuc
loadfull
PnPnVA
nVA
PPVA
VA






Where, if ½ load, hence n = ½ ,
¼ load, n= ¼ ,
90% of full load, n =0.9Where Pcu = Psc
Pc = Poc

30. circuitopenccciron PRIPP  2
)(
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:
02
2
201
2
1
2
2
21
2
1
)()(,
)()(
RIRIPreferredifor
PRIRIPP
cu
circuitshortcucopper



31. Transformer Losses:
• 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).

32. Transformer Losses:
• 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.

33. APPLICATIONS:
• Transformer help us in
making a safe electric power
system which is used to
transfer electricity over long
distances. An electrical
substation in Melbourne,
Australia showing 3 of 5
220kV/66kV transformers,
each with a capacity of
185MVA (shown in figure )
• Transformers with
several secondaries are
used in television and
radio receivers where
several different
voltages are required.

34. APPLICATIONS:
POWER TRANSMISSION :
A major application of transformers is to increase voltage
before transmitting electrical energy over long distances
through wires. Wires have resistance and so dissipate
electrical energy at a rate proportional to the square of the
current through the wire. By transforming electrical power to
a high-voltage (and therefore low-current) form for
transmission and back again afterward, transformers enable
economical transmission of power over long distances .

35. APPLICATIONS:
• IN ELECTRONICS :
• Transformers are also used extensively in electronic
products to step down the supply voltage to a level
suitable for the low voltage circuits they contain. The
transformer also electrically isolates the end user from
contact with the supply voltage .

36. • THERMIC POWER
STATIONS:
The transformer steps
up the generator
voltage (400V or 690V
for low power
stations, 6.3kV or
11kV for higher power
stations) in order to
adapt it to the
network voltage
(generally 20kV)
APPLICATIONS:

37. Transformer must not be connected to a direct source. If the
primary winding of a transformer is connected to a dc supply
mains, the flux produced will not vary but remain constant in
magnitude and therefore no emf will be induced in the
secondary winding except at the moment of switching on.
Thus the transformer can not be employed for raising or
lowering the dc voltage. Also there will be no back induced
emf in the primary winding and therefore a heavy current
will be drawn from the supply mains which may result in the
burning out of the winding.