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Consider the following statements regarding speed control of induction motors by means of external rotor resistors :
1. Reduction in speed is accompanised by reduced efficiency.
2. With a large resistance in the rotor circuit, the speed would vary considerably with variation in torque.
3. The method is very complicated.
The disadvantage of such a method of speed control would include
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- 1 and 3
- 2 and 3
- 1 and 3
- 1, 2 and 3
Correct Option: A
T4 > T3 > T2 > T1
It is seen from the figure that, variation in the speed, as the torque varies between T1 and T2, is more on curve 2 than that on curve 1.
