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Why synchronous motor runs at a fixed speed?
what is the name of that fixed speed?

Answers were Sorted based on User's Feedback

Why synchronous motor runs at a fixed speed? what is the name of that fixed speed?..

Answer / guest

Synchronous motor runs on the principle of MAGNETIC LOCKING
between two fields.

1)Armature field:Produced when a 3 phase balanced supply is
given to 3 phase balanced armature winding at stator.
Armature field rotates at synchronous speed.The direction
of rotation is given by the phase sequence of 3 phase

2)DC field:Rotor is brought up to synchronous speed by
external means in the same direction as that of rotation of
armature field. At the instant of MAGNETIC LOCKING(when the
speed of armature field and the speed of rotor are equal)
DC supply is given to DC field winding at rotor.

Motor runs at fixed speed which is called SYNCHRONOUS SPEED
as long the locking is there.

Is This Answer Correct ?    12 Yes 5 No

Why synchronous motor runs at a fixed speed? what is the name of that fixed speed?..

Answer / navya.suryadevara

Synchronous motor works on magnetic locking principle.
When Ac supply connected to the stator of the synchronous
motor a rotating magnetic field will be produced in the
stator winding.
Dc supply is connected to the rotor of the synchronous motor
produces a field.
At the instant of stator field equal to rotor speed magnetic
locking obtained in the synchronous motor.
Because of this synchronous motor runs at fixed speed.
Fixed speed means synchronous speed which depends on the
number of poles and supply frequency.

Is This Answer Correct ?    6 Yes 2 No

Why synchronous motor runs at a fixed speed? what is the name of that fixed speed?..

Answer / avinash

Synchronous speed is the speed at which the stator field magnetisation is rotating, which depends on supply frequency and number of poles.

Rotor of the synchronous motor is a magnet that can LOCK with the rotating stator field and rotate at synchronous speed.

Rotor has to be externally brought to synchronous speed of the stator then it will continue at synchronous speed provided load is within limit.

Synchronous motor will rotate either at synchronous speed or come to stop.

Is This Answer Correct ?    1 Yes 0 No

Why synchronous motor runs at a fixed speed? what is the name of that fixed speed?..

Answer / shankarj23

In motor, there is a factor called slip. Due to which there
is difference between the actual speed (synchronous) and
resultant speed.

In synchronous motor, the slip is 0. that's the reason why
it runs at synchronous speed.

The fixed speed is called SYNCHRONOUS SPEED.

s= (Ns - N)/Ns


Is This Answer Correct ?    3 Yes 9 No

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