# commutator

[ kom-yuh-tey-ter ]

## noun

1. Electricity.
1. a device for reversing the direction of a current.
2. (in a DC motor or generator) a cylindrical ring or disk assembly of conducting members, individually insulated in a supporting structure with an exposed surface for contact with current-collecting brushes and mounted on the armature shaft, for changing the frequency or direction of the current in the armature windings.
2. Mathematics. the element equal to the product of two given elements in a group multiplied on the right by the product of the inverses of the elements.

commutator

/ ˈkɒmjʊˌteɪtə /

## noun

1. a device used to reverse the direction of flow of an electric current
2. the segmented metal cylinder or disc mounted on the armature shaft of an electric motor, generator, etc, used to make electrical contact with the rotating coils and ensure unidirectional current flow

commutator

/ kŏmyə-tā′tər /

1. The arrangement of contact points in an electric motor connecting an external direct current power supply and the rotating electric coils that use the power, used to generate the AC voltages needed by the coils. The commutator is located at the rotating shaft of the motor, where two power contacts are swept underneath two metal brushes, supplying positive and negative voltage to the coils. When the motor has rotated 180 degrees, the power contacts are each moving under the opposite brush, reversing the polarity of the voltage supplied to the coils.
2. In a group or an algebra, an element of the form ghg −1h −1 where g and h are elements of the group or algebra. If g and h commute , the commutator is the identity element. The commutator is often written [ g , h ].

## Word History and Origins

Origin of commutator1

First recorded in 1830–40; commutate + -or 2

## Example Sentences

The gong and commutator were removed and the magnet placed in the position shown in the sketch.

A small commutator, H, should now be made as follows: Obtain a piece of thin brass tubing about 5/8 in.

The beam was attached to the skate wheel with two small bolts which were insulated and carried two brushes as commutator contacts.

The commutator rings were made of heavy brass strips, fastened to a round piece of wood which was attached to the metal standard.

Another small nut is placed on the end of the shaft, away from the commutator, so that its outside surface is 1/2 in.