Which type of motor is known to run at a constant speed?

A synchronous motor is known for running at a constant speed because it operates in synchronization with the frequency of the electrical supply. In a synchronous motor, the rotation speed of the motor's magnetic field matches the frequency of the power supply, leading to a steady speed regardless of load variations. This characteristic allows synchronous motors to maintain consistent performance in applications where precise speed control is essential.

Unlike other types of motors, such as the universal motor and asynchronous motor, which can experience speed fluctuations with changes in load, the synchronous motor's operation is inherently tied to the AC supply frequency. Servo motors also provide precise control but operate based on feedback systems that allow for variable speeds and positions, rather than maintaining a constant speed like synchronous motors.