TRANSFORMER: History, Uses, Applications

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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
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. 
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.
Transformer equivalent circuit
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:
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
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.
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
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.
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.
Classification of transformer:
As per core:
Core type
Shell type
As per cooling system
Self-cooled
Air cooled
Oil cooled
As per phase
single phase
Three phase
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
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.
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. 
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. 
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.
Transformer classified as per phase :
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
 
Also ,A wide variety of transformer designs are used for different applications:
Auto-transformer
Poly-phase transormer
Leakage transformer
Resonant transformer
Instrument transformers 
Calculation
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.
Where, if ½ load, hence n = ½ ,
 ¼ load, n= ¼ ,
 90% of full load, n =0.9
Where Pcu = Psc
 Pc = Poc
Transformer Losses:
Generally, there are two types of losses;
Iron losses :- occur in core parameters
Copper losses :- occur in winding resistance
Iron Losses: 
ii Copper Losses: 
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).
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.
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.
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 .
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 .
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:
  
 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.