INDUCTION MOTOR
In olden days DC machines are widely used due to its
smooth speed control and production of high starting
torque
After few decade AC Machines replaced DC machines
due to following reasons
HISTORY
INDUCTION MOTOR
Availability of AC supply ( Generation is AC Supply)
AC Machines are simple and rugged constructions
High Efficiency and reasonably good power factor
High reliability
Design and maintenance cost is Low
Simple starting arrangement
Advantages of AC Machines over DC
Machines
INDUCTION MOTOR
it works on the principle of Induction so called
Induction motor
WHAT IS INDUCTION
There is no electrical connection from main supply to
rotor winding, stator winding is directly connected to
AC source, where as rotor winding receives Energy
from stator by means of INDUCTION
Working Principle of Induction motor
INDUCTION MOTOR
Induction motor consist of two parts
Stationary part known as STATOR
Rotating part known as ROTOR
And these two are separated from each other by
small air-gap (about 0.4 mm to 4 mm)
Construction
INDUCTION MOTOR
iron (or) steel yoke (frame)
Hollow, cylindrical core made of silicon steel with
laminations
Slots on the inner periphery of the laminated core
Insulated conductor ( called stator winding)
Star connected
Delta connected
Constructionof stator
INDUCTION MOTOR
Constructionof stator
INDUCTION MOTOR
Hollow, cylindrical core (slotted on outer periphery)
shaft
Conductors ( called rotor winding)
Constructionof Rotor
INDUCTION MOTOR
Depending on the winding connections rotors are of two
types
Squirrel cage Rotor
Wound (or) Slip ring rotor
types of Rotor
INDUCTION MOTOR
Laminated cylindrical core
having parallel slots on its outer periphery
Conductor or winding
which is placed in each slot
End rings
All these conductors joined at each end
by metal rings called end rings as shown
Equivalent circuit
Squirrel cage Rotor
INDUCTION MOTOR
Squirrel cage Rotor
INDUCTION MOTOR
Laminated cylindrical core
having a 3-phase star winding
One side of winding short circuited and
other End connected to 3 slip ring
Brushes
Each slip ring is connected to brushes
Slip Ring Rotor
INDUCTION MOTOR
Slip Ring Rotor
INDUCTION MOTOR
Slip Ring Rotor
a
a’
Single N turn coil carrying current i
Spans 180
o
elec
Resultant flux
Principle of operation
Single N turn coil carrying current i
Spans 180
o
elec
b'
b
Resultant flux
Principle of operation
Single N turn coil carrying current i
Spans 180
o
elec
c'
c
Resultant flux
Principle of operation
3-PHASESINUSOIDALLYDISTRIBUTEDWINDINGS
WAVE SPACE
DISTRIBUTIONS
INDUCTION MOTOR
Depending upon the rotor connections induction
motors are two types
Squirrel cage induction motor
Slip ring induction motor
Types of INDUCTION
MOTORS
INDUCTION MOTOR
The rotor winding is short circuited at each end
by metal rings called end rings
The motor which is designed with squirrel cage
rotor called squirrel cage induction motor
SQUIRREL CAGE INDUCTION
MOTOR
INDUCTION MOTOR
One side of the windings are short circuited and
other ends are brought out and connected to slip
rings (mostly star connected)
The motor which is designed with slip ring rotor
called slip ring induction motor
SLIP RING INDUCTION
MOTOR