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Presented By

Sai Krishna14G25A0217Dept. of EEEASCET-GDR

Guide:G.Venkateswarlu,M.Tech.

An A.C. device used to change high voltage low current A.C. into low voltage high current A.C. and vice-versa without changing the frequency

In brief,1. Transfers electric power from one circuit to

another2. It does so without a change of frequency3. It accomplishes this by electromagnetic

induction4. Where the two electric circuits are in mutual

inductive influence of each other.05/03/23 DEPT OF EEE 2

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It is based on principle of MUTUAL INDUCTION. According to which an e.m.f. is induced in a coil when current in the neighbouring coil changes.

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• Windings are wrapped around the center leg of a laminated core.

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• Windings are wrapped around two sides of a laminated square core.

• The HV and LV windings are split into no. of sections

• Where HV winding lies between two LV windings

• In sandwich coils leakage can be controlled

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Fig: Sandwich windings

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1. When current in the primary coil changes being alternating in nature, a changing magnetic field is produced

2. This changing magnetic field gets associated with the secondary through the soft iron core

3. Hence magnetic flux linked with the secondary coil changes.

4. Which induces e.m.f. in the secondary.

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V1 – supply voltage ; I1- noload input current ; V2- output voltgae; I2- output currentIm- magnetising current; E1-self induced emf ; E2- mutually induced emf

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Fig shows the Phasor diagram of a transformer on load by assuming1.No voltage drop in the winding2.Equal no. of primary and secondary turns

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Fig. a: Ideal transformer on load

Fig. b: Main flux and leakage flux in a transformer

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No load equivalent circuit:

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•Transferring primary side parameters to secondary side

Similarly exciting circuit parameters are also transferred to secondary as Ro’ and Xo’

Since the noload current is 1% of the full load current, the nolad circuit can be neglected

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voltageload-novoltageload-fullvoltageload-noregulationVoltage

1

212 NNVV

DEPT OF EEE 2005/03/23

p

s

p

sNN

VV

recall

Secondary voltage on no-load

V2 is a secondary terminal voltage on full load

1

21

21

21

regulationVoltage

NNV

VNNVSubstitute we have

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leadingfor '-' and laggingfor '' V

sincosV

Vregulation %

luesprimary va of In termsleadingfor '-' and laggingfor ''

Vsincos

VV

regulation %

valuessecondary of In terms

1

10111011

1

'21

20

20222022

20

220

where

XIRIV

where

XIRIV

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Transformer efficiency is defined as (applies to motors, generators and transformers):

%100in

out

PP

%100

lossout

out

PPP

Types of losses incurred in a transformer:Copper I2R lossesHysteresis lossesEddy current losses

Therefore, for a transformer, efficiency may be calculated using the following:

%100cos

cos xIVPP

IV

SScoreCu

SS

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Core or Iron loss:

Copper loss:

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The load at which the two losses are equal =

Transformer is used to step up or down the voltages

Used to transmission & distribution systems

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THANK YOU…

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ANY QUERIES…?