Universal Motor

A universal motor is an electric motor that can run on either alternating or direct current, built as a commutated series wound motor whose stator field coils are wired in series with the rotor windings through a commutator, so the same electromagnet stator that would normally only work on direct current instead works on AC as well. On alternating current, the current in both the field coils and the armature reverses polarity together, in step, so the resulting torque keeps turning the rotor in one consistent direction rather than reversing with the supply. Universal motors combine high starting torque, high running speed and light, compact construction, which is why they power portable tools and household appliances such as blenders, vacuum cleaners and drills, though the commutator brushes wear over time, and the motors are typically noisy both acoustically and electromagnetically, so they suit intermittent rather than continuous duty.