Correct Answer - Option 3 : 400 rpm
Concept of slip:
- The speed of the rotor structure with respect to stator structure is Nr
- With the rotor running at Nr, the relative speed of the stator rotating magnetic field with respect to the rotor conductors is Ns - Nr in the direction of Ns
- This relative speed is referred to as slip speed.
Where Ns is the synchronous speed of the machine
\(N_s =\frac{120f}{p}\)
Where,
f is the frequency of the machine
p is the number of poles of the machine
Slip speed = Ns - Nr
\(slip,s = \frac{(N_s - N_r)}{N_s}\)
Calculation:
Given that, poles (P) = 6
Frequency (f) = 50 Hz
Speed (Nr) = 600 rpm
Synchronous speed Ns = 120f / P = 120 × 50 / 6 = 1000 rpm
Slip speed = Ns - Nr = 1000 - 600 = 400 rpm
Note: In the official paper frequency is not mentioned, but we considered frequency as 50 Hz, other for different frequencies different answers are possible,