Correct Answer - Option 2 :
4%
Concept:
In a 3-phase induction motor, the synchronous speed can be calculated as
\({N_s} = \;\frac{{120f}}{P}\)
\(s = \;\frac{{{N_s} - {N_r}}}{{{N_s}}}\)
Where, Ns = Synchronous speed in rpm,
Nr = Rotor speed in rpm,
s = Slip of the machine,
f = Supply frequency in Hz,
P = Number of poles,
Calculation:
\({N_s} = \frac{{120 \times 50}}{6} = 1000\;rpm\)
\(s = \frac{{1000 - 960}}{{1000}} = 0.04\)
