# Calculate the highest speed at which a 60 Hz alternator can be operated.

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Calculate the highest speed at which a 60 Hz alternator can be operated.
1. 3600 rpm
2. 3000 rpm
3. 2400 rpm
4. 4200 rpm

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Correct Answer - Option 1 : 3600 rpm

Concept:

Synchronous speed of synchronous machine can be calculated as

${N_s} = \frac{{120f}}{P}$

Where,

f = Supply frequency in Hz

P = Number of poles

Ns = Synchronous speed in rpm

Calculation:

Given, f = 60 Hz

To get the maximum speed, the poles must be minimum.

Poles, P = 2

$\therefore {N_s} = \frac{{120 \times 60}}{{2}}$

NS = 3600 rpm