Editing Commutator (electric) (section)

==Principle of operation==
[[Image:Collecteur commutateur rotatif.png|thumb|400px]]
A commutator consists of a set of contact bars fixed to the rotating shaft of a machine, and connected to the armature windings. As the shaft rotates, the commutator reverses the flow of current in a winding. For a single armature winding, when the shaft has made one-half complete turn, the winding is now connected so that current flows through it in the opposite of the initial direction.  In a motor, the armature current causes the fixed magnetic field to exert a rotational force, or a [[torque]], on the winding to make it turn. In a generator, the mechanical torque applied to the shaft maintains the motion of the armature winding through the stationary magnetic field, inducing a current in the winding. In both the motor and generator case, the commutator periodically reverses the direction of current flow through the winding so that current flow in the circuit external to the machine continues in only one direction.

===Simplest practical commutator===
{| style="width:200px; float:right; border:1px solid #ccc; background:#f9f9f9; font-size:88%; line-height:1.5em;"
| [[Image:Simplest Possible Commutator - Rotor View.JPG|140px]]
| [[Image:Simplest Possible Commutator - Brushes.JPG|150px]]
| [[Image:Simplest Possible Commutator - Motor Body.JPG|150px]]
|}
Practical commutators have at least three contact segments, to prevent a "dead" spot where two brushes simultaneously bridge only two commutator segments. Brushes are made wider than the insulated gap, to ensure that brushes are always in contact with an armature coil.  For commutators with at least three segments, although the rotor can potentially stop in a position where two commutator segments touch one brush, this only de-energizes one of the rotor arms while the others will still function correctly. With the remaining rotor arms, a motor can produce sufficient torque to begin spinning the rotor.

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