All induction motors are asynchronous motors. The asynchronous nature of induction-motor operation comes from the slip between the rotational speed of the stator field and somewhat slower speed of the rotor. It is also possible to find induction motors containing rotors made up of windings rather than a squirrel cage.
Keeping this in consideration, what is synchronous speed and actual speed?
In a motor, synchronous speed is the speed at which the magnetic field rotates. Depending on motor design, the actual mechanical speed may be equivalent (synchronous motor) or slightly smaller (asynchronous motor). The synchronous speed is a function of: The electrical frequency used, typically 60 Hz or 50 Hz.
What is the meaning of rated speed?
Rated Operating Speed (RPM) The motor's Rated Operating Speed will be given in RPM, (revolutions per minute) and is the speed the motor will rotate when producing its rated horsepower and supplied its rated voltage. The nameplate shown indicates a rated speed of 1765 RPM for this 4-pole, 60 cycle motor.