Consider the following statements regarding speed control methods of three-phase induction motor

1. We can get speeds greater than the synchronous speed if we inject emf in phase opposition with the existing rotor emf.

2. Two induction motors are said to be cumulatively cascaded when torque produced by them acting in the same direction.

3. Rotor resistance method is not economical for a wide range of speed control.

Which of the above statement(s) is/are correct?