# Synchronous Speed

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Synchronous speed, abbreviated as $$n_{sync}$$, is the speed at which the magnetic field rotates in a synchronous machine, such as an electric motor or generator.  It is directly related to the frequency of the alternating current (AC) power supply and the number of poles in the machine.  The speed decreases as the number of poles increases.

It's important to note that synchronous speed represents the ideal speed of rotation for the magnetic field and is not necessarily the actual speed of the rotor (the rotating part) in a motor or generator.  In practical situations, the actual speed may be slightly less than synchronous speed due to factors such as mechanical losses and slip in motors.

### Synchronous Speed formula

$$N_s = 120\; f \;/\; P$$     (Synchronous Speed)

$$f = N_s \; P \;/\; 120$$

$$P =120\; f \;/\; N_a$$

Symbol English Metric
$$N_s$$ = synchronous speed $$rev\;/\;min$$ $$rev\;/\;min$$
$$f$$ = frequency $$Hz$$ $$s^{-1}$$
$$P$$ = number of poles $$dimensionless$$

### Synchronous Motor Speed RPM (No Load)

The speed decreases as the number of poles increases.

No. of Poles Speed at 50 Hz Speed at 60 HZ
2 3000 3600
4 1500 1800
6 1000 1200
8 750 900
12 500 600
14 428 514
16 375 450
18 334 400
20 300 360

Tags: Electrical Magnetic