Synchronous Speed

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