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3 Phase Induction Motor

The document discusses different types of electric motors. It describes 3 phase induction motors as having a stator with 3 phase windings and a rotor with short circuited windings. Only the stator is powered which induces voltage in the rotor through electromagnetic induction, causing it to rotate. DC motors operate based on a force produced on a conductor carrying current within a magnetic field. Synchronous motors have a permanent magnet rotor that rotates in sync with the rotating stator magnetic field at the same frequency as the power supply.

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Nikesh More
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528 views12 pages

3 Phase Induction Motor

The document discusses different types of electric motors. It describes 3 phase induction motors as having a stator with 3 phase windings and a rotor with short circuited windings. Only the stator is powered which induces voltage in the rotor through electromagnetic induction, causing it to rotate. DC motors operate based on a force produced on a conductor carrying current within a magnetic field. Synchronous motors have a permanent magnet rotor that rotates in sync with the rotating stator magnetic field at the same frequency as the power supply.

Uploaded by

Nikesh More
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as PDF, TXT or read online on Scribd
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3 phase induction motor

3 phase induction motor.


Like any electric motor, a 3-phase induction motor has
a stator and a rotor.
The stator carries a 3-phase winding (called stator
winding) while the rotor carries a short-circuited winding
(called rotor winding).
Only the stator winding is fed from 3-phase supply.
The rotor winding derives its voltage and power from
the externally energized stator winding through
electromagnetic induction
It is a “transformer type” a.c. machine in which
electrical energy is converted into mechanical energy.
 three windings reach there maximum current at
different times.
 so the magnetic field can be considered to rotate
around the stator poles.
Rotation of magnetic field is much smoother than that
of single phase motor.
They are self starting motors.
D.C Motor principle
Value of mechanical force

F = B i L Newton
Value of mechanical force
There are two conditions which are necessary to
produce a force on the conductor.
The conductor must be carrying current, and must be
within a magnetic field. When these two conditions
exist, a force will be applied to the conductor
 which will attempt to move the conductor in a
direction perpendicular to the magnetic field
 This is the basic theory by which all DC motors
operate.
The force exerted upon the conductor can be
expressed as follows.
F = B i L Newton
D.C.Motors classification

Series wound motor Shunt wound motor


D.C.Motors classification

Compound motor Separately excited motor


Three phase synchronous motor
 synchronous motors have similar type of stator those
of induction motor.
 rotor is a permanent magnet.
Here magnetic field produced by the stator rotates.
 so the permanent magnet also rotates with it.
The magnetic filed rotates at 360 degrees in one cycle
of current supply.
So the frequency of the rotation is same that as
frequency of the current supply.
They are not self starting.
Used when precise speed is required.
Advantages & Disadvantages of A.C motors
Advantages:-
It has simple and rugged construction.
It is relatively cheap.
It requires little maintenance.
It has high efficiency and reasonably good power
factor.

Disadvantages:-
It is essentially a constant speed motor and its speed
cannot be changed easily.

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