simple and basic

1. AC MOTORS
presented
by
S.NARESH
( electrical engineer)

2. What is meant by motor?
• A machine which converts electrical energy into mechanical energy is called as motor.
• Motor is divided into two types depend upon the supply:
AC MOTOR
DC MOTOR

3. AC MOTOR
• A machine which converts electrical energy(alternating current)into mechanical energy is called
ac motor.
Ac motor is divided into three types they are:
Three phase motors
Single phase motors
Special motors
Types of three phase motors :
 induction motor
 synchronous motor
The types and working of induction motor is discussed as follows.

4. TYPES OF THREE PHASE INDUCTION
MOTOR.
• Depend upon the rotor construction there are two types:
SQUIRREL CAGE IM
SLIP RING IM

5. Principle and working of induction motor
• Induction motor works on the principle of mutual induction .
• It is also called as rotating transformer.
• It is a self starting one .
• When the three phase supply is given to the stator the rotating
magnetic flux(RMF) is produced .(120f/p=Ns).
• Depend upon the poles and frequency the rotating magnetic field
speed get varied.
• For 50hz,4 pole the RMF speed is 1500rpm.

6. Contd…
• This rotating magnetic field induces emf in the rotor due mutual
induction.
• Due to rotor short circuit the starting current is more.so we need a
starter for induction motor.
• According to the right hand thumb rule ,current carrying conductor
produces magnetic flux.
• So rotor produces magnetic flux.

7. Contd…
• Then both flux are added and cancelled each other depend upon the
polarity.
• Then rotor exerts a force from high flux area to low flux area .
• Likewise it starts to rotate.

8. SQUIRREL CAGE MOTOR
• In this motor, rotor cannot have any windings. There is only a copper
or aluminum bars.
• The conductor bars are short circuited by end rings.
• And there no possibility to add any external resistance to rotor.
• So starting current cannot be controlled and it lead to voltage sag.

9. SLIP RING OR WOUND MOTOR
• In this motor ,rotor have three phase windings.
• External resistance can be added to rotor conductor.
• So, the starting current can be controlled.

10. THANK YOU