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Question
Why we should use delta connection in primary and star 
connection in an distribution transformer, which converts 
400v a.c. voltage to 33kv.
 Question Submitted By :: Electrical-Engineering
I also faced this Question!!     Answer Posted By  
 
Answer
# 1
We use in star connection in seconday connection becouse
need neutal point in load sied( some load supply need 3
phase and some need single phase)but it is remember that
only star connection use in distrubution side transformer.
 
Is This Answer Correct ?    74 Yes 27 No
Engr. Abdul Barek, Electrical
 
Answer
# 2
the answer of Mr. RVG is correct. But I would like to
correct the question itself. Distribution transformer
converts voltage from 33KV to 400V, not 400V to 33KV.
 
Is This Answer Correct ?    54 Yes 8 No
Suresh Kumar
 
 
 
Answer
# 3
Star connection having multiple option of voltages, and
availability of neutral point makes useful for earth fault
relay operation.

Delta connection having requirement of 3 conductors and
itself is long distance, with less current and higher
voltage. So economical way is delta at high voltage side
and star at low/ or consumer end.
 
Is This Answer Correct ?    46 Yes 12 No
Rvg
 
Answer
# 4
we dont need nuetral at primary side but it is needed at
sec. side because some loads of 3 ph and single phase loads
required nuetral.
 
Is This Answer Correct ?    44 Yes 18 No
R M Koloi
 
Answer
# 5
For distribution transformers, loads are connected to
secondry side. hence, requirement of neutral can be
obtained by connecting secondry of the transformer in star.
Secondly, to reduce or minimise the third harmonics in the
transformers, primary side connection generally done in
delta.
 
Is This Answer Correct ?    15 Yes 3 No
Pankaj Malhotra
 
Answer
# 6
we should use delta connection in primary and star to
secondary because in delta line voltage = pphase voltage
and instar line voltage = 1.732phase voltage hence we get
173.2% more voltage hence we use delta star transformer.
 
Is This Answer Correct ?    11 Yes 2 No
Nitin Palaskar
 
Answer
# 7
in secondary side there is a chance for single phase load,
three phase load, if its single phase load added more there
is a chance for unequal voltage in each phases. here we
need one neutral point that is refered as a reference
potential for load equalise the phase voltages
 
Is This Answer Correct ?    7 Yes 3 No
Siva
 
Answer
# 8
WE USE DELTA CONNECTION AT PRIMARY AND STAR CONNECTION AT
SECONDARY IN CASE IF STEP UP OF VOLTAGE REQUIREMENT BECAUSE
IN DELTA/STAR TRANSFORMER THE OUT PUT VOLTAGE WILL BE 1.413
TIMES HIGHER THAN THE PHASE VOLTAGE EVEN WHEN BOTH HAVING
SAME NUMBER OF TURN. SO THE SECONDARY WILL REQUIRE LESS
INSULATION.
 
Is This Answer Correct ?    8 Yes 7 No
Swayanjit
 
Answer
# 9
Primary function of Distribution Transformer is to step-
down 33kv into 440v..while designing the transformer we
have to consider conductor size also...in delta side line
current=1.732 times phase current and in star side phase
current=line current...as we know current is directly
proportional to cross-section of the conductor..keeping in
mind about the cost factor of conductor on load side they
prefer star connection on load side..Guys i tried to
explain in different way..i agree with above answers
also
 
Is This Answer Correct ?    1 Yes 0 No
Gangadhar
 
Answer
# 10
Generally we recevied power supply from HT.In HT side there
will be not available neutral source so in primery side we
given delta connection.But in secondary side we must need
nuetral for three phase & single phase equipments so we
will create from oueself (create from earthings) so here
the connection must be a star connection.
 
Is This Answer Correct ?    0 Yes 1 No
Ravishankar.m
 

 
 
 
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