What are the two classes of 3 Phase Motors?

The correct classification of three-phase motors is based on their operational principles. Synchronous motors run at a speed that is synchronized with the frequency of the supply current. This means that the rotor of the motor turns at the same speed as the rotating magnetic field generated by the stator.

On the other hand, asynchronous motors, which are commonly referred to as induction motors, operate at a speed that is slightly less than the synchronous speed. This difference in speed allows for the production of torque, achieved through the principle of electromagnetic induction, where the rotor experiences a slip.

This distinction between synchronous and asynchronous is fundamental in motor design and application, leading to different uses depending on the requirements for speed control, torque, and efficiency in various industrial applications. Synchronous motors are often used where precise speed control is necessary, while induction motors are preferred for their robustness and simplicity in various operational contexts.

The alternatives provided do not correctly represent the two main classes of three-phase motors based on their operational principles.