The synchronous speed of a four-pole, 60 Hz motor is:

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Multiple Choice

The synchronous speed of a four-pole, 60 Hz motor is:

Explanation:
Synchronous speed is found from the relation n_s = 120 f / P, where f is the supply frequency and P is the number of poles. With a 60 Hz supply and four poles, n_s = 120 × 60 / 4 = 1800 RPM. This is the speed the rotor would run at if there were no slip between the rotating magnetic field and the rotor; in real motors, the rotor actually runs slightly slower due to slip. For context, fewer poles yield higher speeds (two poles give 3600 RPM) and more poles yield lower speeds (eight poles give 900 RPM).

Synchronous speed is found from the relation n_s = 120 f / P, where f is the supply frequency and P is the number of poles. With a 60 Hz supply and four poles, n_s = 120 × 60 / 4 = 1800 RPM. This is the speed the rotor would run at if there were no slip between the rotating magnetic field and the rotor; in real motors, the rotor actually runs slightly slower due to slip. For context, fewer poles yield higher speeds (two poles give 3600 RPM) and more poles yield lower speeds (eight poles give 900 RPM).

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