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05/03/23 DEPT OF EEE 1
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…?