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Question
1.	What is the difference between ac induction motor 
and ac synchronous motor?
 Question Submitted By :: Electrical-Engineering
I also faced this Question!!     Answer Posted By  
 
Answer
# 1
inducton motor is self starting but ac synchronud motor is
not self starting..and induction motor is single excited
but synchronus motor is doubly excited..
 
Is This Answer Correct ?    49 Yes 11 No
Amit Kumar Srivastava
 
Answer
# 2
The basic difference between an induction motor(a.c) and a
synchronous AC motor is that in the latter a current is
supplied onto the rotor. This then creates a magnetic field
which, through magnetic interaction, links to the rotating
magnetic field in the stator which in turn causes the rotor
to turn. It is called synchronous because at steady state
the speed of the rotor is the same as the speed of the
rotating magnetic field in the stator.

By way of contrast, the induction motor does not have any
direct supply onto the rotor; instead, a secondary current
is induced in the rotor. To achieve this, stator windings
are arranged around the rotor so that when energised with a
polyphase supply they create a rotating magnetic field
pattern which sweeps past the rotor. This changing magnetic
field pattern can induce currents in the rotor conductors.
These currents interact with the rotating magnetic field
created by the stator and the rotor will turn.
 
Is This Answer Correct ?    39 Yes 4 No
Pramod
 
 
 
Answer
# 3
main difference is syncronous motor widely used for
powerfactor correction in industrial and also to carry the
load.but induction motor can use only to carry the load.

induction motor can run at any speed.but synchronous can
run at only one speed.
 
Is This Answer Correct ?    45 Yes 11 No
V.selvakumar
 
Answer
# 4
1. Synchronous motor runs at synchronous speed but the
induction moror can't, if it does so then it will stop
because the rotor conductors will not cut the magnetic
field & induction principle will fails.
2. Synchrounous motor can improve power factor but
induction motor can't.
3. Synchrounous motor is costly as compared to induction
motor.
4. Synchrounous motor has two types excitations but in
induction motor has only one type excitation.
5. Synchronous motor can't run at other speed without
synchronous speed, if it does so then it will fall out of
synchronism & will stop.
6. There is requirement of any auxilary help for starting
the synchronous motor like pony motor,with the help of
manual rotation, by inserting the copper cage into its own
rotor(means starting as squirrel cage motor), but there is
no requirement of any help to start the induction motor.
 
Is This Answer Correct ?    23 Yes 5 No
Amritpal Singh Sidhu
 
Answer
# 5
induction motor is a self starting motor&it is single
excited machine.
but synchronous is a not a self starting machine&it is a
doubly excited machine.
in syncronous motor we connect rotor to dc supply due to
inertia
 
Is This Answer Correct ?    5 Yes 4 No
Ponnu(the Elite)
 
Answer
# 6
Always turn at less than synchronous speed.
Do not require control.
Much cheaper to produce (true for squirrel cage
machines).
Self-starting.
Less efficient than synchronous machines.
More suitable for explosive environments.
No maintenance (for squirrel cage machines). Synchronous
machines:
Wound-rotor or permanent magnet to generate the
rotor magnetic field.
Rotor magnetic field is stationary with respect
to the rotor.
Always turn at synchronous speed.
Require some form of control to operate.
More expensive to produce than squirrel cage
induction machines.
Not self-starting.
More efficient than induction machines.

Induction Machines:
Wound-rotor or squirrel cage to generate the
rotor magnetic field.
Rotor magnetic field rotates with respect to the
rotor.
 
Is This Answer Correct ?    3 Yes 2 No
Jadeja
 
Answer
# 7
inducton motor is self starting but ac synchronud motor is
not self starting..and induction motor is single excited
but synchronus motor is doubly excited..
 
Is This Answer Correct ?    1 Yes 0 No
Ravi
 
Answer
# 8
Above answers are ok.

If you want more, get diploma 4th sem Electrical machines 2
book.
You have get clear knowledge about the motor
 
Is This Answer Correct ?    13 Yes 13 No
Stanley Electrician
 
Answer
# 9
1. Synchronous motor is not self starting, but induction
motor is self starting.
2. In synchronous motor, a d.c. supply is required for rotor
excitation. But in induction motor, d.c. supply is not required.
3.By adjusting the d.c. field excitation of synchronous
motor, it can be made to operate from lagging to leading
p.f. But 3-phase induction motor always operates at low
lagging p.f.
4. Synchronous motor can be used for variable speed
operations because it runs at synchronous(or one) speed at
all loads. But induction motor can be used for variable
speed operations because it's speed vary with the loads.
5. Synchronous motor requires high cost as compared to
induction motor.
 
Is This Answer Correct ?    2 Yes 2 No
Tajmera
 
Answer
# 10
AC SYNCHRONOUS MOTOR CAN BE USED FOR CORRECTION OF POWER
FACTOR WHEREAS AC INDUCTION MOTOR CANNOT BE USED FOR THIS
PURPOSE
 
Is This Answer Correct ?    2 Yes 3 No
Mahajan Devendra
 

 
 
 
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