Transformer

1. TransformerTransformer
Presented by –Presented by –
Md Sazedul IslamMd Sazedul Islam
ID: 143010048ID: 143010048
Electrical & Electronics EngineeringElectrical & Electronics Engineering
Green University Of BangladeshGreen University Of Bangladesh

2. What is Transformer ??What is Transformer ??
 A transformer is aA transformer is a
static device which isstatic device which is
use to convert highuse to convert high
alternatic voltage toalternatic voltage to
a low alternatica low alternatic
voltage and vicevoltage and vice
versa, keeping theversa, keeping the
frequency same.frequency same.

3. Principle Of OperationPrinciple Of Operation
 Transformer works on theTransformer works on the
principle of mutualprinciple of mutual
induction of two coils.induction of two coils.
When current in theWhen current in the
primary coil is changed theprimary coil is changed the
flux linked to the secondaryflux linked to the secondary
coil also changes.coil also changes.
Consequently an EMF isConsequently an EMF is
induced in the secondaryinduced in the secondary
coil.coil.

4. What is Induction law ??What is Induction law ??
Faraday’s law states that:Faraday’s law states that:
Vs=Ns.dVs=Ns.dΦΦ/dt/dt
wherewhere VSVS is the instantaneous secondryis the instantaneous secondry
winding voltage.winding voltage.
NSNS is the number of turns in the secondaryis the number of turns in the secondary
coil.coil.

5. Working….Working….
When the primary winding is connected to anWhen the primary winding is connected to an
ac supply mains, current flows throughac supply mains, current flows through
it. winding produces an alternating flux init. winding produces an alternating flux in
the core. Since this flux is alternating andthe core. Since this flux is alternating and
links with the secondary winding also, solinks with the secondary winding also, so
induces an emf in the secondary winding. Theinduces an emf in the secondary winding. The
frequency of induced emf in secondaryfrequency of induced emf in secondary
winding is the same as that of the flux or thatwinding is the same as that of the flux or that
of the supply voltage. The induced emf in theof the supply voltage. The induced emf in the
secondary winding enables it to deliversecondary winding enables it to deliver
current to an external load connected acrosscurrent to an external load connected across
it. Thus the energy is transformed fromit. Thus the energy is transformed from
primary winding to the secondary winding byprimary winding to the secondary winding by
means ofmeans of electro-magnetic inductionelectro-magnetic induction withoutwithout
any change in frequency. any change in frequency.

6. Types of TransformerTypes of Transformer
 Step UP TransformerStep UP Transformer ::
A transformer in which Ns>Np is called a step upA transformer in which Ns>Np is called a step up
transformer. A step up transformer is a transformer whichtransformer. A step up transformer is a transformer which
converts low alternatic voltage to high alternatic voltage.converts low alternatic voltage to high alternatic voltage.
 Step DOWN TransformerStep DOWN Transformer ::
A transformer in which Np>Ns is called a step downA transformer in which Np>Ns is called a step down
transformer. A step down transformer is a transformertransformer. A step down transformer is a transformer
which converts high alternatic voltage to low alternaticwhich converts high alternatic voltage to low alternatic
voltage.voltage.

7. Construction of TransformerConstruction of Transformer
Mainly Transformers haveMainly Transformers have
two types oftwo types of
construction….construction….
 CORE type constructionCORE type construction
 SHELL type constructionSHELL type construction

8. Core type TransformerCore type Transformer
In the Core typeIn the Core type
the primary andthe primary and
secondary windingssecondary windings
are placed on eachare placed on each
side of the core.side of the core.
The core type hasThe core type has
two limbstwo limbs

9. Shell type TransformerShell type Transformer
In Shell typeIn Shell type
transformers thetransformers the
LV & HVLV & HV
windings arewindings are
sandwichedsandwiched
between each other.between each other.
shell type has threeshell type has three
limbs.limbs.

10. For designs of Transformer are used forFor designs of Transformer are used for
different applications.different applications.
 Auto-transformerAuto-transformer
 Poly-phase transormerPoly-phase transormer
 Leakage transformerLeakage transformer
 Resonant transformerResonant transformer
 Instrument transformersInstrument transformers

11. AUTO-TRANSFORMERSAUTO-TRANSFORMERS
Autotransformer is aAutotransformer is a
one windingone winding
transformer in whichtransformer in which
a part of the windinga part of the winding
is common to bothis common to both
HV & LV sides.HV & LV sides.

12. Transformer equivalent circuitTransformer equivalent circuit

13. Losses In Transformers….Losses In Transformers….
Iron Losses –Iron Losses – These are theThese are the
hysteresis loss and eddyhysteresis loss and eddy
current loss, constant loss.current loss, constant loss.
Each time the magnetic field isEach time the magnetic field is
reversed, a small amount ofreversed, a small amount of
energy is lost dueenergy is lost due
to hysteresis within the core.to hysteresis within the core.
TheThe eddy current losseddy current loss is ais a
complex function of the squarecomplex function of the square
of supply frequency andof supply frequency and
inverse square of the materialinverse square of the material
thicknessthickness
 Copper Loss :CurrentCopper Loss :Current
flowing through theflowing through the
windingswindings
causes resistivecauses resistive
heating of theheating of the
conductors. At higherconductors. At higher
frequencies, skinfrequencies, skin
effect and proximityeffect and proximity
effect createeffect create
additional windingadditional winding
resistance andresistance and
losses.losses.

14. TestingTesting
Open circuit testOpen circuit test
Short circuit testShort circuit test