Answer / nm

3 phase induction motor operates on the principle of
induction due to rotating magnetic field.....

3 phase t/f will not act like a motor because the primary
coils in induction motor are placed at 120 degrees spacially
in space which is not ther in t/f so rotating magnetic fld
which is the cause of rotation will not be produced...

Answer / ravi693

In 3 phase squirrel cage induction motor, due to electro
magnetic induction emf is induced in rotor circuit. This
emf produced the rotor magnetic field. We have alreade
stator magnetic field. A revolving magnetic field set up
and motor start running.

If 3 phase t/f is placed on bearings and powered up. It
will not rotate due to following reasons.
1) T/F secondary is open circuited and small current is in
secondary side. Less field is there. No revolving field is
set up.
2) Design parameters are there. Which did not produce
revolving magnetic field.

Answer / ranjeet mukherjee

In 3phase induction motor,when 3 phase supply is given,a
rotating and constant magnetic field is developed in the
air gap between rotor and stator.This magnetic field is cut
by rotor bars,so an emf is induced in the rotor bars.As the
rotor is short circuited from both end so a current will
flow in the bars.The direction of this current will be such
that it will oppose the cause which is producing it(Lenz's
Law).Here in this case the cause is the relative speed
between the rotating magnetic field and the standstill
rotor.So the rotor starts rotating in the direction of the
magnetic field so that it cathes the speed of the magnetic
field and reduce the relative speed between them.
Although the principal of working of 3phase induction motor
and transformer are same but in case of transformer there
is no relative speed between primary and secondary windings
magnetic field.Moreover both the windings are placed in
same core and there is no air gap between the magnetic
fields of the windings.Both the flux are in same core.So it
is not possible to rotate a transformer even though it is
placed in bearings.

Answer / urvish mehta

firstly rotor of the induction motor rotates
due to the effect of rotating magnetic field
while in the transformers pulsating magnectic
field is produced not rotating...


The transformer components don't rotate (or move at all) simply because they are rigidly mounted. If you suspend a thin wire in the air close to an iron object, and pass a current through the wire, it will move, being attracted toward the iron by the magnetic field produced by the current.
Motors are specially arranged with the magnetic field in just the right spot so that it acts on the armature to cause rotation. Of course the armature rides on bearings so it can rotate.
Transformers have no components that are free to move, and the magnetic field is directed so as to induce a voltage in the secondary winding. That's what transformers do. Nothing inside the transformer is free to rotate.
Interestingly, if you ever get a chance to stand near a large transformer, you will hear a buzz or humming sound. This is the wires and iron core actually moving a very tiny amount as the magnetic field acts on them. There is no rotation though, just a small vibration back and forth as the magnetic field builds and collapses.

Answer / ramesh pachamal

Due to the rotating magnetic field in the stator induces an
emf in the rotor. As the rotor rings are short circuited a
current will flow through the rotor bars.As per the
faradays law, a current carrying rotor bar at magnetic
field it excerts force causes to rotate.

As the induction motor is called as rotating transformer,
the concept in both the group is same as mutual induction.
A modification of transformer can be done to rotate. This
is the purpose a heavy steelbelt is provided in the
secondary of the transformer normally. Eventhough the
secondary get force and will make airgap inside the winding
giving noise.(inductive reactance)

Answer / rajesh

even we keep a transformer connected in star or delta,it
dont rotate why because there is a specific placement of
armature conductors to exert a torque on it.

simply saying we don't get a superb curry by mixing all the
spieces. we get it only through a specific exercise.

Answer / surendra verma

For rotating a machine there will need some torque,and it is
rule in machine that to provide torque there should be
necessrly two interactive relative stationry field ,niether
avg.torque will be zero,now in case of transformer one field
is present on time varying axis; where is other field with
which first field will interact..no where...so it is totally
ridiclous to ask such silly questin in which only one field
is available..what can i talk about 120 phase displacement
concept of space winding when this primary conditon is not
satsfied itself.......

Answer / princealekota

In 3 phase squirrel cage induction motor, emf is induced in
rotor circuit. This produces the magnetic field in rotor.
Since we are giving supply to the stator stator magnetinc
field is developed which is revolving and rotor follows the
field. Like rotor speed is following the synchronous speed.

But, in 3phase transformer will not rotate when it is
placed on bearings. Because field developed in the
transformer is not revolving.

Answer / zaved

In SCIM emf induced on the principle of dynamically induced
efm & phase displacement is 120 degrees apart
tras. work on the principle of statically induced emf

Answer / narendra mahadik

motor consist of magnetic field if electric supply given to
motor flux produced in to it due to its magnetic field &
due to maggnetic field produced in it emf iduced in its &
rotation of rotor start .

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