Why, the starting current of 3 phase Induction Motor is 7
to 8 times its rated current?

Answers were Sorted based on User's Feedback



Why, the starting current of 3 phase Induction Motor is 7 to 8 times its rated current?..

Answer / roysayan01

From the equivalent circuit of an induction motor it can be
seen that the the expression of current is

I=E/[(jX1+R1)+(jX2+R2/s)

Generally during running condition slip,s=0.03
i.e the value of slip is very low which increases the
resistance (R2/s) in the above eqn and as a result of which
current decreases

but

at starting s=1 and so the resistance (R2/s) is small and
the current is 7 to 8 times higher than the current during
running condition.

Hope i explained it vividly.
For ny doubt or query feel free to mail me at
roysayan01@gmail.com

Is This Answer Correct ?    46 Yes 2 No

Why, the starting current of 3 phase Induction Motor is 7 to 8 times its rated current?..

Answer / esha

The starting current, sometimes called inrush current will be 8-10 times higher than the motor's rated current because the motor is at rest.
When at rest, the motor appears to be a transformer, with it's secondary winding short circuited, i.e. the rotor winding or squirrel cage is a closed circuit. This results in a low impedance to the system voltage and the motor has a "locked rotor" current of typically 6 times full load current, but also up to 8 and sometimes 10 times current.
This starting value is independent of any load attached, however, the inertia of the motor and load has to be overcome. This is especially true when the motor is connected to a load, like a conveyor belt with product on it. The larger the inertia, the longer the motor takes to reach full speed.
As the motor accelerates, part of the starting current power overcomes this inertia and is conveted to kinetic energy.
info from-wikianswer.com

Is This Answer Correct ?    13 Yes 3 No

Why, the starting current of 3 phase Induction Motor is 7 to 8 times its rated current?..

Answer / vinay singh

the air gap path provide more reluctance path to the mutual
flux but mutual flux is constant due to constant applied
voltage. so for constant mutual flux the magnetising m.m.f.
is more and stator draws more magnetising current during
starting.

Is This Answer Correct ?    5 Yes 3 No

Why, the starting current of 3 phase Induction Motor is 7 to 8 times its rated current?..

Answer / sdkarwa

because end rings of the squirell cage induction motor are
shorted

Is This Answer Correct ?    6 Yes 8 No

Why, the starting current of 3 phase Induction Motor is 7 to 8 times its rated current?..

Answer / s.eltarhoni

i confirm that the obove two answers are right and the
second is more detailed but i would like you to answer why
this case appeares only at starting

Is This Answer Correct ?    1 Yes 3 No

Why, the starting current of 3 phase Induction Motor is 7 to 8 times its rated current?..

Answer / richard

during starting time there wont be back emf so it takes 7
to 8 times high current

Is This Answer Correct ?    6 Yes 8 No

Why, the starting current of 3 phase Induction Motor is 7 to 8 times its rated current?..

Answer / stalin raj

The motor needs high torque to starts its rotation.The
torque is directly proportional to the square of the
current.Hence it takes a large current at starting.

Is This Answer Correct ?    7 Yes 9 No

Why, the starting current of 3 phase Induction Motor is 7 to 8 times its rated current?..

Answer / mukhesh

because end rings of the squirell cage induction motor are
shorted so resistance is small it offers that much of
currentt here is no windings but in slip to improve the st
torques windings are present it offers low current than sqirrel

Is This Answer Correct ?    3 Yes 7 No

Why, the starting current of 3 phase Induction Motor is 7 to 8 times its rated current?..

Answer / zakir_vjti20

email me at zakir_vjti20@yahoo.com

Is This Answer Correct ?    2 Yes 12 No

Post New Answer

More Electrical Engineering Interview Questions

how many testing is necessary for 27 MVA transformer?

1 Answers  


What is the exact load current needed for a place which has 100nos of bulb of each 100w?

2 Answers  


control & auxilary circuits used for circuir breakers

0 Answers  


What is the technical name of minute currents that i have been produced in moving electrical objects?

2 Answers   ITC Infotech,


400Kv,can it be generated?why?

2 Answers  






I had applied for JE in PSEB, Can you pls send me the Question bank for related to my field

0 Answers  


1.what is meaning of curve into a mcb. 2.what is basic reason changing of curve

0 Answers  


If u have 60KVA UPS, than tell me how systems ( computers ) u may connect?

3 Answers   Thomson Reuters,


How do i right a ladder diagram that has 1 actuator that performs a full stroke followed by a half stroke

0 Answers   Tata Motors,


What is the technical reason for adopting color coding of three phase system as RYB.

11 Answers   ABB, ERDA,


why power is generatd at 50 hz only..? can we do this on another freq...?

7 Answers  


What are the types of class b amplifier?

0 Answers  


Categories
  • Civil Engineering Interview Questions Civil Engineering (5085)
  • Mechanical Engineering Interview Questions Mechanical Engineering (4452)
  • Electrical Engineering Interview Questions Electrical Engineering (16638)
  • Electronics Communications Interview Questions Electronics Communications (3918)
  • Chemical Engineering Interview Questions Chemical Engineering (1095)
  • Aeronautical Engineering Interview Questions Aeronautical Engineering (239)
  • Bio Engineering Interview Questions Bio Engineering (96)
  • Metallurgy Interview Questions Metallurgy (361)
  • Industrial Engineering Interview Questions Industrial Engineering (259)
  • Instrumentation Interview Questions Instrumentation (3014)
  • Automobile Engineering Interview Questions Automobile Engineering (332)
  • Mechatronics Engineering Interview Questions Mechatronics Engineering (97)
  • Marine Engineering Interview Questions Marine Engineering (124)
  • Power Plant Engineering Interview Questions Power Plant Engineering (172)
  • Textile Engineering Interview Questions Textile Engineering (575)
  • Production Engineering Interview Questions Production Engineering (25)
  • Satellite Systems Engineering Interview Questions Satellite Systems Engineering (106)
  • Engineering AllOther Interview Questions Engineering AllOther (1379)