A SIMPLE explanation of the Synchronous Speed in Synchronous Motors. Learn what Synchronous Speed is, how it is achieved, and the formula behind it. You can read more about Synchronous Speed control in Synchronous Motors at: https://www.electrical4u.com/speedco...

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Synchronous motors are constant speed motors. They run at the synchronous speed of the supply. They are generally used for constant speed operation under no load conditions such as to improve the power factor. Synchronous motors have fewer losses than induction motors at a given rating. The speed of a synchronous motor is given by N_s = 120f / p. Using this, we can calculate the motor rpm.

As you can see, the synchronous speed depends on the frequency of the supply and the number of poles of the rotor. Changing the number of poles is not easy, so we do not use that method. However, with the invention of solidstate devices, the frequency of the current fed to the synchronous motor can be varied. We can control the speed of the synchronous motor by changing the frequency of the supply to the motor. We can use a combination of rectifiers and inverters to control the speed of synchronous motors.