Calculate the speed of the 8-pole alternator if the supply frequency is 50 Hz. 

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SSC JE Electrical 4 Dec 2023 Official Paper II
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  1. 1500 rpm
  2. 1000 rpm
  3. 500 rpm
  4. 750 rpm

Answer (Detailed Solution Below)

Option 4 : 750 rpm
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Detailed Solution

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Concept:

The synchronous speed of a synchronous machine is given by

\({N_s} = \frac{{120f}}{P}\)

Where f is frequency and P is the number of poles.

A synchronous machine always rotates at a synchronous speed.

Calculation:

Number of poles (P) = 8

Frequency (f) = 50 Hz

Synchronous speed, \({N_{s}} = \frac{{120 \times 50}}{8} = 750~rpm\)

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