Synchronous speed refers to the speed at which the rotating magnetic field produced by an alternating current (AC) power supply rotates in a synchronous motor. In an ideal synchronous motor, the rotor (the moving part of the motor) rotates at this synchronous speed.
Synchronous speed is determined by the frequency of the AC power supply and the number of poles in the motor. The formula to calculate synchronous speed (Ns) is:
=
120
×
Ns=
P
120×f
Where:
Ns = Synchronous speed in revolutions per minute (RPM)
f = Frequency of the AC power supply in hertz (Hz)
P = Number of poles in the motor
For example, if you have a 4-pole motor connected to a 60 Hz power supply, the synchronous speed would be:
=
120
×
60
4
=
1800
RPM
Ns=
4
120×60
=1800RPM
Synchronous motors are often used in applications where precise speed control is required, such as in industrial processes, power generation, and synchronous clocks. They operate at a constant speed that's synchronized with the frequency of the power supply. However, in practical situations, synchronous motors are not always able to maintain exact synchronous speed due to factors like load changes and mechanical losses.