This presentation describes the Principle of Operation - Squirrel cage Induction motor Classification of Induction motors Rotating Magnetic flux- Relative Motion - Faradays law- Lenz law

1. INDUCTION MOTORS & DRIVES
Classifications
Three Phase Induction Motor
-Squirrel Cage Induction Motor
-Slip ring Induction Motor
Single Phase Induction Motor
-Split Phase Induction Motor
-Capacitor start Induction Motor
-Capacitor run Induction Motor
-Shaded Pole Induction Motor

2. CONSTRUCTION OF THREE PHASE SQUIRREL CAGE INDUCTION MOTOR
Rotor
Stator
Air gap

3. What is Relative motion?
100 km/hr
Stationary
YES! There is a Relative Motion here
Train 1
Train 2
Train 1
Train 2
100 km/hr
100 km/hr
NO! Here Relative Motion = “0” here

4. THREE PHASE SQUIRREL INDUCTION MOTOR
(Principle of Operation)
HOW ELECTRICAL ENERGY TO MECHANICAL ENERGY?

5. Step 1:
Create Rotating Magnetic Flux (RMF) in stator
What is RMF & How to Create it?
Magnetic
Flux
Rotating
(RMF)

6. RMF CREATION
(USING THREE PHASE SUPPLY)
When a three phase supply is given to a three phase windings and each
windings are displaced by 120 degree then the resultant will be a
Rotating magnetic flux (RMF)
Schematic Structure

7. Step 2 : The RMF created in the stator cuts the stationary conductor in
the rotor and creates induced EMF – (Because of F.L.E.M.I)
Rotating Magnetic Flux
(RMF)
Induced EMF in Stationary
Conductors
Rotor conductors
(Stationary)
Faradays Law of
Electromagnetic
Induction (F.L.E.M.I)
Ns = 120 f /P
( due to Relative Motion b/n
magnetic flux & conductor)

8. Step 3 : The induced EMF in the rotor opposes the very cause i.e. Relative
motion between RMF and Stationary conductor
Rotating Magnetic Flux
(RMF)
Induced EMF
- due to Relative motion
Rotor conductors
(Stationary)
Oppose the very cause (i.e Relative
motion b/n Magnetic flux &
conductors) and try to make
Relative motion = ZERO
Ns

9. Step 4 : As the result rotor conductors will rotate in the same direction
of RMF
Rotating Magnetic Flux
(RMF)
Induced EMF
Rotor conductors Oppose the very cause
(i.e. Relative motion b/n RMF
& stationary conductors) &
try to make R.M = 0
As the result rotor conductors rotates in
the same direction of RMF
Ns
N
- due to Relative motion

10. Important Note: Rotor speed (N) will never reach the RMF speed (Ns). So only there
will be continuous opposition and continuous rotation
Rotor conductors
(Rotating)
Ns
N
Condition: N < Ns
• No Relative Motion
• So No induced EMF
• So No opposition or Lenz law
• So NO ROTATION IN THE ROTOR!
SLIP SPEED (SNs) = Ns- N
What happen when Ns = N?
or Slip speed = zero?

11. Rotating Magnetic Flux
(RMF)
Induced EMF
Rotor conductors
(Stationary)
Ns
How do the torque created in rotor to rotate in
same direction of RMF?
Current
(Short circuited
Rotor Conductor)
Flux created
in rotor
TORQUE !!

12. SUMMARY
Rotating Magnetic Flux
(RMF)
Induced EMF
- due to Relative motion
Rotor conductors Lenz law try to
make Relative Motion = 0
As the result rotor rotates in
the direction of RMF
& SLIP SPEED = Ns- N
Ns
N
Current
(S.C)
Flux
(Rotor)
TORQUE!