Universal motor

The universal motor is an electric motor that can run on either alternating or direct current and uses an electromagnet as its stator. It is a commutated series-wound motor, with the field coils connected in series with the rotor windings through a commutator, which is why it is often called an AC series motor. Because the current in the field and the armature reverses together on AC, the force keeps the same direction of rotation. Universal motors have high starting torque, run at high speed and are light and compact, so they are common in portable power tools and household appliances. Their brushes wear and they are typically noisy, so they suit equipment that is not in continuous use.