3-phase induction motors are widely used in industrial applications due to their rugged, low maintenance construction. They operate by creating a rotating magnetic field in the stationary stator windings using 3-phase power which induces a current in the short-circuited rotor windings, causing the rotor to turn. Squirrel cage induction motors are most common due to their low cost but slip ring motors provide higher starting torque. Both have a torque-slip characteristic where torque decreases with speed until the rotor reaches synchronous speed. Common applications include pumps, fans and other loads requiring continuous operation.

1. TOPIC- 3 phase induction motor
Presented-Ajit Kumar verma
EN-15
Roll no- 1501421003

2. 3 PHASE INDUCTION MOTOR
content
• Introduction
• Types of Electrical Machines
• Types of 3-Ph induction motor
• Basic Principle
• Working Principle
• Components of induction motor
• Comparison between 1-ph I.M. & 3-ph I.M
• Torque-slip & torque-speed characteristic
• Application

3. INTRODUCTION
• Electrical Machines are Electromechanical
energy conversion devices.
• Electrical motor coverts electrical energy into
mechanical energy and electrical generators
are vice versa.
• Most of the Industrial load are inductive,
especially 3-ph induction motors are widely
used in industrial applications for continuous
operation.

4. Types of Electrical Machines
• 1.AC Machines
• 2.DC Machines
• AC Machines:
• 1-Ph Induction Motor
• 3-Ph Induction Motor
• Synchronous motor
• 1- Ph Transformer
• 3-ph Transformer
• Alternator or AC Generator

5. DC Machines:
DC Motor:
 DC Shunt Motor
• DC Series Motor
• DC Compound Wound Motor
DC Generator
• DC Shunt Generator
• DC Series Generator
• DC Compound Wound Generator

6. Basic Principle of 3-phase IM
 A Rotating Magnetic field (RMF) is set up in
the stator when a 3- Phase supply is given.
The stationary rotor cut the revolving field and
due to electromagnetic induction an e.m.f. is
induced in the rotor conductor.
 As the rotor conductor is short circuited
current flows through them.
 It becomes a current carrying conductor in
magnetic field and start rotating.

7. Induction motor rotor always rotate at a
speed less than synchronous speed.
The difference between the flux (Ns) and the
rotor speed (N) is called slip.
% Slip (s) ={(Ns – N)/ Ns} *100
 Where Ns=Synchronous Speed N= Actual
Speed of rotor
Slip speed = (Ns – N)

8. Types of 3phase IM
According to rotor construction it can be Classified
in two category according to rotor Construction
1. Squirrel cage induction motor
2. Slip ring induction motor

9. Components of induction motor
Frame
Stator
 Stator Winding
 Rotor
 Rotor Winding
Cooling Fan
Bearings

10. Frame: Frame provides mechanical support to the
stator and rotor. It is made from casting materials.
Stator: It is stationary part of induction motor. It
consists stator winding It is housed on the motor
frame.
Rotor: It is housed on the shaft of the induction
motor.
• It has two ends, one is called Driving end and
another is called non Driving end.

11. • mechanical load is connected on driving end
while cooling fan is connected on non-driving
end.
• Both the ends are connected with bearings
for free rotation means of reduced friction
losses.
• Stator Windings: (1)-Star connected
(2)-Delta connected
• Rotor Windings: It is wound as rotor bars and
short circuited at both the ends through end
rings.

12. Comparison between
SRIM & WRIM
 Squirrel cage Induction Motor:
1. Most of the application of industrial as well as domestic
are this type of induction motor.
2. Its construction is simple and rugged.
3. Cheap compare to slip ring IM
4. Maintenance is easy
5. Cost is less compare to slip ring IM
6. Can use at explosive area
7. Starting torque is low compare to slip ring IM
 Application: Leath machine, Compressors , centrifugal
pump, in agriculture etc. where cost is most important
factor

13. Slip ring Induction Motor:
1. It has high starting torque compare to
squirrel cage IM
2. Construction is complicated
3. Maintenance cost is high compare to squirrel
cage IM Starter requires compulsory
4. Can not use at explosive area
 Application:- Crane , hoist , lift and where
high starting torque is required

14. Induction Motors and Transformers
Both IM and transformer works on the principle of
induced voltage –
• Transformer: voltage applied to the primary
windings produce an induced voltage in the
secondary windings –
• Induction motor: voltage applied to the stator
windings produce an induced voltage in the rotor
windings –
• The difference is that, in the case of the induction
motor, the secondary windings can move –
• Due to the rotation of the rotor (the secondary
winding of the IM), the induced voltage in it does
not have the same frequency of the stator (the
primary) voltage

15. Torque- slip& torque speed
characteristic

16. • The induction motor is work in 3 modes
(1)-breaking mode
(2)-motoring mode
(3)-generating mode
The speed-torque curve

17. Application
• Crane , hoist ,lift and where high starting
torque is require.
• It is also used for industrial application.

18. Thank you