The induced emf frequency is slip times the frequency of applied voltage. Since emf in induction motor is induced when stator flux cut the rotor conductor so the emf actually is induced only due to their relative speed i.e Ns-Nr (Ns=synchronous speed of stator flux and Nr=rotor speed in RPM) between them.

F=sF it is when the system is loaded at their rated load and F=F when the system is on no laod

Induction Motor and Induced EMF

An induction motor is a type of AC motor that works on the principle of electromagnetic induction. It consists of a stator and a rotor. The stator is the stationary part, while the rotor is the rotating part. When an AC power supply is connected to the stator winding, a rotating magnetic field is produced. This rotating magnetic field induces an EMF (electromotive force) in the rotor, which causes it to rotate.

Frequency of the Induced EMF

The frequency of the induced EMF in an induction motor is the same as the supply frequency. This means that the induced EMF has the same frequency as the AC power supply that is connected to the stator winding.

Explanation

When an AC voltage is applied to the stator winding of an induction motor, it produces a rotating magnetic field. This rotating magnetic field cuts the conductors of the rotor, which in turn induces an EMF in the rotor windings. The induced EMF in the rotor is responsible for the production of torque, which causes the rotor to rotate.

The frequency of the induced EMF is determined by the speed at which the magnetic field rotates. In an induction motor, the speed of the rotating magnetic field is determined by the frequency of the AC power supply and the number of poles in the motor.

The speed of the rotating magnetic field is given by the formula:

Speed = (120 * Frequency) / Number of Poles

Since the speed of the rotating magnetic field is directly proportional to the frequency of the power supply, the frequency of the induced EMF in the rotor is also the same as the supply frequency.

Conclusion

In conclusion, the frequency of the induced EMF in an induction motor is the same as the frequency of the AC power supply. This is because the speed of the rotating magnetic field, which determines the frequency of the induced EMF, is directly proportional to the supply frequency. Therefore, the correct answer is option 'C' - the frequency of the induced EMF is the same as the supply frequency.