Which condition must be maintained for the proper operation of an Asynchronous Motor?

For an asynchronous motor, also known as an induction motor, the fundamental principle behind its operation is the slip between the rotor speed and the synchronous speed of the magnetic field. The magnetic field generates a rotating magnetic field that induces current in the rotor. In order for the motor to function properly, the speed of this magnetic field must exceed the speed of the rotor. This difference in speed, known as slip, is crucial because it allows the rotor to experience a change in magnetic flux, which is necessary for inducing the current that generates torque.

If the rotor were to reach synchronous speed, there would be no relative motion between the rotating magnetic field and the rotor. Consequently, no induced electromotive force (EMF) would be produced in the rotor, and thus no torque would be generated to drive the motor. This means that maintaining a condition where the speed of the magnetic field exceeds the rotor speed is essential for the continuous operation and torque production of the motor.

The other choices do not accurately represent the conditions necessary for the proper operation of an asynchronous motor. For instance, equal phase voltages contribute to balanced operation but are not a fundamental operational requirement for generating torque in an induction motor. Similarly, the relationship between stator and rotor currents varies depending on load