Calculate synchronous speed for a 4-pole motor on 60 Hz.

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Multiple Choice

Calculate synchronous speed for a 4-pole motor on 60 Hz.

Explanation:
Synchronous speed is the speed at which the stator’s magnetic field rotates and it’s determined by the supply frequency and the number of poles. The formula is Ns = 120 f / P, with f in hertz and P the number of poles. For a 60 Hz supply and a 4-pole machine: Ns = (120 × 60) / 4 = 7200 / 4 = 1800 RPM. So the synchronous speed is 1800 RPM. In practice, an induction motor’s rotor runs a bit slower than this due to slip, but 1800 RPM is the exact synchronous speed. For context, 2 poles at 60 Hz gives 3600 RPM, 6 poles gives 1200 RPM, and 8 poles gives 900 RPM.

Synchronous speed is the speed at which the stator’s magnetic field rotates and it’s determined by the supply frequency and the number of poles. The formula is Ns = 120 f / P, with f in hertz and P the number of poles. For a 60 Hz supply and a 4-pole machine: Ns = (120 × 60) / 4 = 7200 / 4 = 1800 RPM. So the synchronous speed is 1800 RPM. In practice, an induction motor’s rotor runs a bit slower than this due to slip, but 1800 RPM is the exact synchronous speed. For context, 2 poles at 60 Hz gives 3600 RPM, 6 poles gives 1200 RPM, and 8 poles gives 900 RPM.

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