The efficiency of a 60 Hz, 6-pole, 1000 rpm 3-phase induction motor is ________.

Correct option is A

$$\text{Given that, number of poles } (P) = 6 \\[4pt]\text{Frequency } (f) = 60\,\text{Hz} \\[4pt]\text{Synchronous speed } (N_s) = \frac{120f}{P} = 1200\,\text{rpm} \\[4pt]\text{Rotor speed } (N_r) = 1000\,\text{rpm} \\[8pt]\text{Efficiency, } \eta = \frac{1000}{1200} \times 100 = 83.33\%$$​​