A constant speed motor is an electric motor, powered by direct current, in which both the armature windings and field windings are powered by the same source. A constant speed motor is also referred to as a DC shunt motor.
A constant speed motor works by creating its own electromagnetic field. The EMF, created by the rotating armature, creates resistance, which holds the motor to a certain speed. A load placed on the motor slows the armature, which reduces the resistance of the field. The reduced resistance allows the motor to return to its normal speed. By balancing resistance and load, the motor maintains a constant speed under various work conditions.