For a three‑phase 60 Hz motor with 6 poles rotating at 1157 rpm, what is the percent slip?

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Multiple Choice

For a three‑phase 60 Hz motor with 6 poles rotating at 1157 rpm, what is the percent slip?

Explanation:
In induction motors, percent slip measures how far the rotor lags behind the rotating magnetic field to develop torque. It’s defined as s = (Ns − Nr)/Ns × 100%, where Ns is the synchronous speed and Nr is the rotor speed. For a three-phase motor, Ns = 120 f / P. With f = 60 Hz and P = 6, Ns = 120 × 60 / 6 = 1200 rpm. The rotor is turning at Nr = 1157 rpm, so the difference is 1200 − 1157 = 43 rpm. Percent slip = (43 / 1200) × 100% ≈ 3.58%. So the slip is about 3.58%.

In induction motors, percent slip measures how far the rotor lags behind the rotating magnetic field to develop torque. It’s defined as s = (Ns − Nr)/Ns × 100%, where Ns is the synchronous speed and Nr is the rotor speed.

For a three-phase motor, Ns = 120 f / P. With f = 60 Hz and P = 6, Ns = 120 × 60 / 6 = 1200 rpm.

The rotor is turning at Nr = 1157 rpm, so the difference is 1200 − 1157 = 43 rpm.

Percent slip = (43 / 1200) × 100% ≈ 3.58%.

So the slip is about 3.58%.

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