What is synchronous speed of an Alternator

What is synchronous speed:

Let take an alternator, it is a numerical expression where the fixed number of poles, the machine has to be rotated at a particular speed to keep the frequency of the generated emf in constant value. Such a rotating speed is called Synchronous speed of the alternator

Synchronous speed is being notated by Ns

Ns= 120f/P


F= frequency of the alternator

P= number of poles

In India the frequency of an alternating emf is standard and which is equal to 50 Hz. To get the constant frequency for different poles, the alternator rotates at a different speed (synchronous speed). Let see some alternator speed vs Pole to maintain the constant frequency.

P (poles) 2 4 8 12 24
Ns (Synchronus speed) 3000 1500 750 500 250



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