What is the rotating speed of a three-phase 60 Hz 4-pole motor?

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Multiple Choice

What is the rotating speed of a three-phase 60 Hz 4-pole motor?

Explanation:
Rotating speed is governed by the synchronous speed, which depends on the supply frequency and the motor’s pole count. Use n_s = 120 f / P. With a 60 Hz supply and four poles, n_s = 120 × 60 / 4 = 1800 rpm. In operation the rotor actually runs a bit below this due to slip, so the real speed is slightly less under load, but 1800 rpm is the standard reference speed for this configuration. The other pole counts would yield different speeds (for example, a two-pole machine would run at about 3600 rpm, a six-pole at about 1200 rpm, etc.), which is why 1800 rpm is the correct value here.

Rotating speed is governed by the synchronous speed, which depends on the supply frequency and the motor’s pole count. Use n_s = 120 f / P. With a 60 Hz supply and four poles, n_s = 120 × 60 / 4 = 1800 rpm. In operation the rotor actually runs a bit below this due to slip, so the real speed is slightly less under load, but 1800 rpm is the standard reference speed for this configuration. The other pole counts would yield different speeds (for example, a two-pole machine would run at about 3600 rpm, a six-pole at about 1200 rpm, etc.), which is why 1800 rpm is the correct value here.

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