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Question
Why is starter necessary for a three-phase induction motor?
 Question Submitted By :: Ramesh
I also faced this Question!!     Rank Answer Posted By  
 
  Re: Why is starter necessary for a three-phase induction motor?
Answer
# 1
By starting an induction motor with starter limits the
starting current and starting torque .


Note - Upto 5 to 7.5 HP Three phase induction motors
generally started direct on line .
 
Is This Answer Correct ?    175 Yes 27 No
Jessy
 
  Re: Why is starter necessary for a three-phase induction motor?
Answer
# 2
AT THE STARTING OF THREE PHASE INDUCTION MOTOR THE STARTING
CURRENT IS HIGH IT IS DUE TO AT THE STARTING THE BACKEMF IS
0.SO BY USING STARTER WE CAN LIMIT THE STARTING CURRENT
 
Is This Answer Correct ?    115 Yes 37 No
G.v.suresh Kumar
 
 
 
  Re: Why is starter necessary for a three-phase induction motor?
Answer
# 3
The starters are used to limit the starting current to
accepteble value.
 
Is This Answer Correct ?    84 Yes 9 No
Msimanmg
 
  Re: Why is starter necessary for a three-phase induction motor?
Answer
# 4
1--it limit the starting current.
2--increase the starting torque.
 
Is This Answer Correct ?    60 Yes 24 No
Patanjali
 
  Re: Why is starter necessary for a three-phase induction motor?
Answer
# 5
A starter is needed for a three phase induction motor
because at the time of starting, if induction motor is
started directly, it will draw large amount of current
which causes damage to adjoining equipments.
Thus, a starter is needed in order to limit the starting
current.After the motor has started at reduced starting
current and hence reduced voltage, the connections are
diverted towards the mains supply so that now, the motor
can run at higher starting current and voltage.
Four types of starting methods are employed:
1.Star-Delta
2.Auto transformer method
3.Primary resistor starting.
4.Direct On-line.
Low rating upto 7 H.P motors can be started directly.
 
Is This Answer Correct ?    186 Yes 8 No
Farha
 
  Re: Why is starter necessary for a three-phase induction motor?
Answer
# 6
at the time of starting slip S= 1, so the rotor resistance
which depends on slip i.e.
R2(1-S)/S will be equzl to "0",
i.e. rotor will act as short circuit.
hence initailly motor will draw heavy amount of current.
So in order to reduce this inrush current(5 to 7 times of
rated current), we apply less input voltage at the time of
starting so that input curent will be low(as in case of
star connection) & after some time or specified time input
will be fed in Delta connection.

if u understand this then ok other wise read more books in
details...
 
Is This Answer Correct ?    74 Yes 9 No
Saurabh
 
  Re: Why is starter necessary for a three-phase induction motor?
Answer
# 7
starter is reqired for the purpose of reduce starting
current. starting current reduce in starting period so that
starting torque is increase. another thing is that if
starter is not provided than high amont of current flow in
starting beacuase of that it may be chances to damege
itself and alose its adjoining m/c.
 
Is This Answer Correct ?    32 Yes 14 No
Bhavik Parekh
 
  Re: Why is starter necessary for a three-phase induction motor?
Answer
# 8
Starter is used to reduce starting current.starting current
is usually large because of inertia,charecteristics of
motor winding(at starting slip=1,rotor resistance low
implies less back emf).So at starting we use starter .for
example.STAR DELTA starter.by using a starter at least the
switching is improved which is much important for safe and
longer life time use.simply a DOL can be used for lower
rated motors (up to 07 HP)in this case.for higher rated
motors (up to 15 HP)we can use a star delta connection.a
delta connected motor takes 1.7 times line current than a
star connectd motor.think ! at starting the current is
almost halved .Now a days we use drives (power electronics
products which not only takes care of starting of a motor
(improving power factor) also controls it as perrequirement.
 
Is This Answer Correct ?    38 Yes 4 No
Abanikanta
 
  Re: Why is starter necessary for a three-phase induction motor?
Answer
# 9
starter is required to limit the high starting current 
Is This Answer Correct ?    26 Yes 6 No
Balasivakami
 
  Re: Why is starter necessary for a three-phase induction motor?
Answer
# 10
when the induction motor starts.slip i.e "s" has a value
1...and hence the internal resistance value becomes
0..since resistance is directly proportinal to (s-1)....as
the resistance becomes 0..according to ohms law current
becomes very high.....tha value of current is about 5 to 6
times the full load curent......therefore the motor must
accelerate to high speed ,,which is not possible at "load"
condition.....and hence the motor may burst due to
overheating.............to prevent the motor from bursting
by reducing the value of current we use a STARTER....
 
Is This Answer Correct ?    16 Yes 5 No
Monika Khatri
 

 
 
 
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