2. SPEED CONTROL OF THREE PHASE
INDUCTION MOTOR
Stator side control
1.Stator voltage control
2.Stator frequency control
3.V/f control
4.Pole changing method
Rotor side control
1.Adding external resistance in the rotor circuit
2.Cascade control
3.Slip power recovery scheme
3. Stator side control
Change in stator voltage
1.Using autotransformer
2.Primery resistors connected in series with stator
winding
11. Changing the number of poles
Synchronous speed of the motor
NS = 120f/P
f=supply frequency
P=number of poles
12.
13.
14. Rotor side control
A. Cascade control
B. Rotor resistance control
C. Slip power recovery scheme
1.Kramer system
i.Conventional method
ii.Static method
2.Scherbius system
i.Conventional method
ii.Static method
17. DISADVANTAGES OF CASCADE CONTROL
This method requires two motors
More expensive
Wide range of speed control is not possible
It cannot be operated when
P1=P2 or P1<P2
20. Slip power recovery scheme
Used to speed control the slip ring induction motor
Speed control by varying the stator voltage or
by controlling the power flow in the rotor circuit
21. Types of Slip power recovery scheme
1.Kramer system
i.Conventional method
ii.Static method
2.Scherbius system
i.Conventional method
ii.Static method