What characterizes a synchronous motor?

A synchronous motor is defined by its ability to operate at a constant speed that is synchronized with the frequency of the alternating current (AC) supply. This characteristic means that its rotor speed is directly linked to the speed of the magnetic field produced by the stator, determined by the AC supply frequency. For example, in a 60 Hz system, the synchronous speed of the motor is calculated to be 1800 RPM (revolutions per minute) for a 4-pole motor.

The steady operation at this synchronized speed is critical for applications where precise speed control is necessary, such as in timing devices or in processes that require uniform motion. Once the motor reaches this speed, it maintains it regardless of the load variations (assuming the load remains within the motor's rated capabilities), which is a distinct advantage for certain industrial applications.

In contrast, synchronous motors are not designed to operate at varying speeds (as described in another choice), nor do they require a large starting torque. They typically run on alternating current rather than direct current, further distinguishing them from other types of motors, such as DC motors.