INDUCTION MOTOR pankajchaudhary582@gmail.com

1. A
SEMINAR ON
“INDUCTION MOTOR”
BACHELOR OF TECHNOLOGY
IN
ELECTRICAL & ELECTRONICS ENGINEERING
SUBMITTED
BY
PANKAJ CHAUDHARY
R.N. - 24823
UNDER THE SUPERVISION OF
ARUNESH DUTT (H.O.D)
DEPARTMENT OF ELECTRICAL & ELECTRONICS ENGINEERING
SANJAY GANDHI INSTITUTE OF ENGINEERING & TECHNOLOGY
NEHRU GRAM BHARATI UNIVERSITY, ALLAHABAD

2.  INTRODUCTION
 CONSTRUCTION
 PRINCIPLE OF OPERATION
*DOUBLE REVOLVING FIELD THEORY
 SQUIRREL CAGE ROTOR
 INDUCTION MOTOR SPEED
 THE SLIP
 STARTING TORQUE
 APPLICATION
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3.  The induction motor is one of ac machine, in which
there are alternating currents in both stator and
rotor windings. The alternating current is supplied
directly to the stator winding and by induction, i.e.
transformer action, to the rotor winding.
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4.  The single-phase motor stator has a laminated
iron core with two windings arranged
perpendicular
- One is the main and
- The other is the auxiliary winding or starting
winding.
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5.  A single phase induction motor has two main parts
namely stator (the one which is stationary) and rotor
(the one which is rotating).
 The stator winding is connected across a single phase
ac supply . The ac supply produces a rotating
magnetic field in the air gap between the stator and
rotor. The field rotates at a speed called synchronous
speed and it is denoted by Ns.
 It is mathematically expressed as,
Ns = 120f/p rpm
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6.  The induction motor actually rotates at a speed which
is slightly less than the synchronous speed.
 The rotor is said to be squirrel cage type. As the
construction of rotor appears to be like the squirrel’s
cage, the name squirrel cage rotor has been used.
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7.  A single phase ac supply is connected to the stator
winding. This forces an alternating current
through the stator winding . This current produce an
alternating flux in the air gap between the stator and
rotor.
 The induced voltage ,a current start flowing through
the conductors. This current will the produce its own
flux called as the rotor flux. The main flux produce
by the stator winding interacts with the rotor flux
to produce the torque.
 It is important to note that the single phase induction
motor are not self starting, like the dc motors
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8. DOUBLE REVOLVING FIELD THEORY-
 A single phase ac supplies the main winding that produces a
pulsating magnetic field.
 The pulsating field is divided a forward and reverse rotating
field.
 Motor is started in the direction of forward rotating field this
generates small (5%) positive slip.
Spos =(nsy –nm)/ nsy
 Reverse rotating field generates a larger ( 1.95 %) negative
slip. Sneg =(nsy + nm)
 Each of the rotating field induces a voltage in the rotor ,
which derives currents and produces torque.
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9.  The bars and end rings together look like a cage and
hence such a rotor is called a cage rotor or a
squirrel cage rotor.
 The rotor consists of copper or aluminium bars
which are permanently short circuited at both the
ends using the conducting rings called end rings.
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10.  So, the IM will always run at a speed lower than the
synchronous speed
 The difference between the synchronous speed
and the motor speed is called the Slip speed.
nslip  nsync  nm
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11. n n
sync m
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sync
s
n


Where s is the slip
* Slip may be expressed as a percentage by
multiplying the above eq. by 100, notice that the
slip is a ratio and doesn’t have units.

12.  The single phase induction motor starting torque is
zero because of the pulsating single phase magnetic
flux
 Two perpendicular coils that have current 90⁰ out of
phase can generated the necessary rotating magnetic
fields which start the motor.
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13. The single phase induction motor of application
are-
-Fans,
- Refrigerators,
-Washing machines
- Drills
-Compressors
- Centrifugal Pumps, etc
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