Editing Electric motor (section)

===Commutator===
{{main|Commutator (electric)}}
[[File:Universal_motor_commutator.jpg|thumb|[[commutator (electric)|Commutator]] in a [[universal motor]] from a vacuum cleaner. Parts: ''(A)'' commutator, ''(B)'' [[brush (electric)|brush]]]]

A [[commutator (electric)|commutator]] is a rotary [[switch|electrical switch]] that supplies current to the rotor. It periodically reverses the flow of current in the rotor windings as the shaft rotates. It consists of a cylinder composed of multiple metal contact segments on the [[armature (electrical engineering)|armature]]. Two or more [[electrical contacts]] called ''[[brush (electric)|brushes]]'' made of a soft conductive material like [[carbon]] press against the commutator. The brushes make sliding contact with successive commutator segments as the rotator turns, supplying current to the rotor. The windings on the rotor are connected to the commutator segments. The commutator reverses the [[current (electricity)|current]] direction in the rotor windings with each half turn (180°), so the torque applied to the rotor is always in the same direction.{{sfn|Hameyer|2001|p=62}} Without this reversal, the direction of torque on each rotor winding would reverse with each half turn, stopping the rotor. Commutated motors have been mostly replaced by [[brushless DC motor|brushless motors]], [[permanent magnet motor]]s, and [[induction motor]]s.