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Laxmi Institute Of Technology, Sarigam
3rd semester :- Electronics & Communication
Engineering
Presentation On :- Construction & E.M.F eqn. of
Transformer
Professor name :- Narendra Bhilwala
PREPARED BY :-
1. Jay Baria - 150860111003
-: Transformer :-
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.
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
NOTE :
It works on the principle of mutual induction
Construction 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.
• 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
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.”
• 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
-:Transformer Construction:-
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.
• 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.
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
Core-type Transformers :-
The coils used are form-wound and are of the
cylindrical type. The general form of these coils may
be circular or oval or rectangular. In small size core-
type transformers, a simple rectangular core is used
with cylindrical coils which are either circular or
rectangular in form.
But for large-size core-type transformers,
round or circular cylindrical coils are used
which are so wound as to fit over a cruciform
core section as shown in Fig. The circular
cylindrical coils are used in most of the core-
type transformers because of their
mechanical strength. Such cylindrical coils are
wound in helical layers with the different
layers insulated from each other by paper,
cloth, micarta board or cooling ducts. Fig.
shows the general arrangement of these coils
with respect to the core.
Shell-type Transformers:-
In these case also, the coils are form-would but are
multi-layer disc type usually wound in the
form of pancakes. The different layers of such multi-
layer discs are insulated from each other by paper.
The complete winding consists of stacked discs with
insulation space between the coils–the spaces
forming horizontal
cooling and insulating ducts.
A very commonly-used shell-type transformer is
the one known as Berry Transformer–so called
after the name of its designer and is cylindrical
in form. The transformer core consists of
laminations arranged in groups which radiate
out from the centre. It may be pointed out that
cores and coils of transformers must be
provided with rigid mechanical bracing in order
to prevent movement and possible insulation
damage. Good bracing reduces vibration and
the objectionable noise–a humming sound–
during operation.
-:EMF Equation of Transformer:-
Let
N1 = No. of turns in primary
N2 = No. of turns in secondary
Φm = Maximum flux in core in webers
= Bm × A
f = Frequency of a.c. input in Hz
flux increases from its zero value to
maximum value Φm in one quarter of the
cycle i.e. in 1/4 f second.
∴ Average rate of change of flux =1/ 4fΦm
= 4 f Φm Wb/s
or volt
Now, rate of change of flux per turn means
induced e.m.f. in volts.
∴ Average e.m.f./turn = 4 f Φm volt
If flux Φ varies sinusoidally, then r.m.s. value of
induced e.m.f. is obtained by multiplying the
averagevalue with form factor.
Form factor =r.m.s. value/ avg. value = 1.11
∴ r.m.s. value of e.m.f./turn = 1.11 × 4 f Φm
= 4.44 f Φm volt
• Now, r.m.s. value of the induced e.m.f. in the
whole of primary winding
= (induced e.m.f/turn) × No. of primary turns
•E1 = 4.44 f N1 Φm = 4.44 f N1 BmA.........(1)
Similarly, r.m.s. value of the e.m.f. induced in
secondary is,
•E2 = 4.44 f N2 Φm = 4.44 f N2 BmA..........(2)
•Equation 1,2 represents the e.m.f equation.
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.
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.
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
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
Construction & E.M.F. eqn. of transformer

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Construction & E.M.F. eqn. of transformer

  • 1. Laxmi Institute Of Technology, Sarigam 3rd semester :- Electronics & Communication Engineering Presentation On :- Construction & E.M.F eqn. of Transformer Professor name :- Narendra Bhilwala PREPARED BY :- 1. Jay Baria - 150860111003
  • 3. 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.
  • 4. 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 NOTE : It works on the principle of mutual induction
  • 5. Construction 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.
  • 6. • 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
  • 7. 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.”
  • 8. • 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
  • 10. 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. • 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.
  • 11. 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
  • 12. Core-type Transformers :- The coils used are form-wound and are of the cylindrical type. The general form of these coils may be circular or oval or rectangular. In small size core- type transformers, a simple rectangular core is used with cylindrical coils which are either circular or rectangular in form.
  • 13. But for large-size core-type transformers, round or circular cylindrical coils are used which are so wound as to fit over a cruciform core section as shown in Fig. The circular cylindrical coils are used in most of the core- type transformers because of their mechanical strength. Such cylindrical coils are wound in helical layers with the different layers insulated from each other by paper, cloth, micarta board or cooling ducts. Fig. shows the general arrangement of these coils with respect to the core.
  • 14. Shell-type Transformers:- In these case also, the coils are form-would but are multi-layer disc type usually wound in the form of pancakes. The different layers of such multi- layer discs are insulated from each other by paper. The complete winding consists of stacked discs with insulation space between the coils–the spaces forming horizontal cooling and insulating ducts.
  • 15. A very commonly-used shell-type transformer is the one known as Berry Transformer–so called after the name of its designer and is cylindrical in form. The transformer core consists of laminations arranged in groups which radiate out from the centre. It may be pointed out that cores and coils of transformers must be provided with rigid mechanical bracing in order to prevent movement and possible insulation damage. Good bracing reduces vibration and the objectionable noise–a humming sound– during operation.
  • 16. -:EMF Equation of Transformer:- Let N1 = No. of turns in primary N2 = No. of turns in secondary Φm = Maximum flux in core in webers = Bm × A f = Frequency of a.c. input in Hz flux increases from its zero value to maximum value Φm in one quarter of the cycle i.e. in 1/4 f second.
  • 17. ∴ Average rate of change of flux =1/ 4fΦm = 4 f Φm Wb/s or volt Now, rate of change of flux per turn means induced e.m.f. in volts. ∴ Average e.m.f./turn = 4 f Φm volt If flux Φ varies sinusoidally, then r.m.s. value of induced e.m.f. is obtained by multiplying the averagevalue with form factor. Form factor =r.m.s. value/ avg. value = 1.11
  • 18. ∴ r.m.s. value of e.m.f./turn = 1.11 × 4 f Φm = 4.44 f Φm volt • Now, r.m.s. value of the induced e.m.f. in the whole of primary winding = (induced e.m.f/turn) × No. of primary turns •E1 = 4.44 f N1 Φm = 4.44 f N1 BmA.........(1) Similarly, r.m.s. value of the e.m.f. induced in secondary is, •E2 = 4.44 f N2 Φm = 4.44 f N2 BmA..........(2) •Equation 1,2 represents the e.m.f equation.
  • 19. 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.
  • 20. 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.
  • 21. 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
  • 22. 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