Answer / avdhesh

The basic differance in star and delta connection is that
in delta connection voltage across the winding is line
voltage (V-line) and in star connection it is phase voltage
(V-line/1.73). Same way current in each winding in delta
connection will be (I-line/1.73) and in star connection it
will be line current(I-line). Now to design any motor one
has to take cost of insulation as well as copper.In delta
connection you need higher insulation and in star
connection you need thick conductor to cary high current.

For HT motors current is less as voltage applied is high
hence to reduce insulation cost star connection is made.

For higher rating LT motors since current is high delta
configuration is recommonded.

If we do not follow above than cost and size of machine
willbe increase.
Hope this is the answer of your question.

Answer / saurabh

During Design it self it is take in consideration
As Power = Torque x Angular Velocity(RPM)

So for same RPM(say 1500 rpm), for Same Input Voltage

1) In star connection Torque will be less hence Power
output will b less

2) In Delta Connection Toruqe will be More hence Power
output will b more

as far as HT motors are concern, in order to limit inrush
current star connection could b given.

Answer / gunasekaran

that is not economical why we r going to high voltage for
high KW rating for reduce the loss. delta connected load is
giving 3 time power output than star.

Answer / shyamal

Thanks Avdhesh for the answer...
Can you tell me whether one can operate star connected motors
with delta connection & vice versa?

Answer / kanth.g

Actually the question is not in Proper way try to get it
right.

i am using star-delta connections with reverse/forward direction motion of the 75hp induction motor.What should be the ratings of Main,Delta and Star contactors and why?

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