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Electrical Engineering QUESTION #2139
Question 1
A $4$-pole induction motor is supplied by a $50\text{ Hz}$ source. If the slip $s$ is $0.04$, what is the actual speed of the rotor $N_r$ in RPM?
  • $1500\text{ RPM}$
  • $1440\text{ RPM}$✔️
  • $1410\text{ RPM}$
  • $1560\text{ RPM}$
Correct Answer Explanation
Synchronous speed $N_s = \frac{120f}{P} = \frac{120 \times 50}{4} = 1500\text{ RPM}$. Rotor speed $N_r = N_s(1 - s) = 1500(1 - 0.04) = 1440\text{ RPM}$.