What are the characteristics of a synchronous motor?

A synchronous motor is distinguished by its ability to operate at a constant speed that is directly synchronized with the frequency of the electrical supply. This means that the motor maintains a consistent rotational speed regardless of the load variations, as long as the frequency of the input power remains constant. This characteristic is critical for applications that require precise speed control, such as in industrial processes or in applications involving synchronization with other machinery.

The design of synchronous motors allows them to achieve this constant speed due to the interaction between the rotating magnetic field produced by the stator and the magnetic field of the rotor, which is made to rotate at the same speed through excitation. This synchronization is essential for systems that need to maintain a specific timing or coordination between various mechanistic components.

In contrast, other options present characteristics that do not accurately describe synchronous motors. For instance, while some motors may have automatic starting sequences, synchronous motors typically require a separate mechanism or auxiliary equipment for starting, as they cannot start under load. Additionally, the statement regarding the need for an external power source is misleading; synchronous motors do not operate entirely without external power because they require an excitation source to produce the rotor's magnetic field. Lastly, synchronous motors are versatile and can be designed for various voltage applications, not limited to