\[N_s=\frac{120f}{P}\]
Variables
Nssynchronous speed (rpm)
felectrical frequency (Hz)
Pnumber of poles
Description
What is this formula?
The synchronous speed equation calculates the rotational speed of the rotating magnetic field produced by an AC machine.
When to use it
Use this formula when analyzing synchronous motors, synchronous generators, induction motors, motor selection, and variable-frequency drive applications.
Example
A four-pole motor operates at:
Frequency = 60 Hz
Poles = 4
Formula:
Ns = 120f / P
Substitution:
Ns = (120 × 60) / 4
Result:
Ns = 1800 rpm
Applications
Synchronous motors
Alternators and generators
Induction motor analysis
Variable-frequency drives
Electrical machine design