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In case of Alternator, the three phases (RYB) are wound on the stator in a sequential manner (R-Y-B-R-Y-B... so on) As we are aware, the three phases are electrically apart by 120deg. so that by adopting such a stator winding, a rotating magnetic field with synchronous speed (120*freq/no. of poles) is developed.
Even an emf is induced in the rotor also, with similar synchronous speed, but owing to large inertia of rotor, it cannot attain synchronous speed and stays standstill.

In case of transformer, the three-phase windings are wound on three limbs - on each limb LV winding is wound on the core and then HV winding is wound over the LV winding (for increased efficiency of transformer). Due to this constructional arrangement, a rotating magnetic field is not visualized in transformer, rather mutual inductance comes in to picture.
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How do you generate sinusoidal voltage?

The most common ways are:Mechanically, by placing a coil in a rotating magnetic field, or a rotating coil in a fixed magnetic field. This is how AC power is generated.Electronically, using an oscillator circuit. This is how sinusoidal waveforms are produced in all sorts of electronic equipment.


Why is an induction motor called rotating transformer?

A motor rotor rotates due to an interaction between magnetic fields of the rotor and stator, where either may use permanent magnets, electromagnets, or a combination of both to effect the interaction. This interaction is based on the principle of opposite attraction and like repulsion related to magnets. Either the rotor or stator creates an electromagnetic field, and the opposite component (rotor or stator) tries to attract and repel the appropriate magnetic poles to 'lock' position with the electromagnetic field. The magnetic field is 'rotated' electrically by applying voltage to different windings within the motor in sequence, and since the moving component always tries to lock position with the magnetic field, the rotor will constantly rotate while trying to align its magnetism.


Why is excitation necessary for synchronous generators?

generators work by rotating a magnetic field thru a wire shell or by rotating wire thru a stationary magnetic field (think of a small DC motor with magnets around the shell) since large generators dont have magnets in them (its not very efficent)you have to send a flowing current thru the rotating coils to produce the magnetic field. this induces current in the stator and you have a generator..of course the same effect is produced by inducing a current in the stator and pulling the output from the rotor.


What makes the armature in the electric motor rotate?

from Faraday's law of electromagnetic induction : when a current carrying conductor cuts the magnetic field an E.M.F (electro motive force) is produced and it sets up in such a direction so as to oppose the cause of it. the stator winding of a motor which produces the R.M.F (rotating magnetic field) serves as the magnetic field and the armature winding is the current carrying conductor which cuts the magnetic field , thus an EMF is induced in the armature which again produces a force to oppose the emf produced in the armature winding.


What is transformer turns ratio excitation current?

This is the current level needed to energize a transformer to its rated voltageThe clue is in the name! 'Excitation' means to create a magnetic field. So the excitation current is the current drawn from the supply which sets up the magnetic field around the core.

Related Questions

Is there any rotating magnetic field in dc motors?

yeah ,if we consider a 3 phase dc motor ,the rotating magnetic field is produced by rotating the permanent magnet with a constant speed.


Why transformer not rotating?

transformer is not rotating bcoz for rotating rotating magnetic field is required which is produced only when the current is passed through the windings which are displaced physically by 120degrees and phase difference of 120 degrees where as in transformer there is no phsical displacement of 120degrees hence transformer cannot rotate.


What is the principle of operation of three phase squirrel cage induction motar?

three phase induction motor is like a rotating transformer, works on the principle of faraday's law of electromagnetic induction. when ever three phase supply is given rotating magnetic field is produced (rotating magnetic field is produced because current flowing through each phase is delayed 6.66mSec) and the stationary conductor (rotor) is cut by the rotating magnatic field so emf is induced in the conductor (rotor) since rotor is short circuited current flows and this current produces magnatic field. magnatic field produced by the rotor interacts with the rotating magnatic field. this interaction of fields produces movement in the conductor(rotor)(since it is allowed to rotate).


What does a Rotating magnetic field do?

The Field which is continuously rotating with a particular axis is known as rotating magnetic field. It will be created in Three phase induction motor's stator. When the supply is given to stator of three induction motor, the flux of each phases (that are displaced by 120 degrees) will interact. Due to this the resultant Field will be rotating Magnetic Field will be Produced.


Name the types of alternators based on their rotor construction?

1) Rotating armature alternator, rotates in stationary magnetic field. 2) Rotating field alternator, the magnetic field is rotating.


How do you prove that a rotating magnetic field is produced when a 3 phase supply fed to a 3 phase winding?

The motor will turn


Why doesn't a transformer work only on a DC supplyand not in ac supply?

A transformer doesn' t work with DC current because voltage is induced in the output winding of the transformer when a magnetic field passes through the coils of this winding. This happens with AC current because the magnetic field is continually expanding and contracting. With a DC current the magnetic field is unchanging other than when you first turn it on. Since the magnetic field is not moving it is not moving through the windings and no voltage is produced.


How do you generate sinusoidal voltage?

The most common ways are:Mechanically, by placing a coil in a rotating magnetic field, or a rotating coil in a fixed magnetic field. This is how AC power is generated.Electronically, using an oscillator circuit. This is how sinusoidal waveforms are produced in all sorts of electronic equipment.


How do you produce eddy current in magnetic drum?

Eddy currents in a magnetic drum can be produced by rotating the drum in close proximity to a magnetic field. The changing magnetic field induces currents in the metal drum, which in turn creates its own magnetic field that interacts with the original field, causing eddy currents to flow within the drum.


What happens in earth interior to produce earths magnetic field describe the layer where the magnetic field is produced?

What escapes the crust is what we observe as the earths magnetic field. The outer core is a rotating mass of fluid metal that induces an electrical current which in turn generates the magnetosphere.


What happens in the Earth's interior to produce Earth's magnetic field describe to layer where the magnetic field is produced?

What escapes the crust is what we observe as the earths magnetic field. The outer core is a rotating mass of fluid metal that induces an electrical current which in turn generates the magnetosphere.


Role of stator and rotor in synchronous and induction motor?

Stator is part of rotating mechanical device thats sorrounds the rotor to rotate it through the induced magnetic field while the Rotor, is the one who is rotated by produced magnetic field in the stator,.