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The Collaborative International Dictionary
Commutator

Commutator \Com"mu*ta`tor\, n. (Elec.) A piece of apparatus used for reversing the direction of an electrical current; an attachment to certain electrical machines, by means of which alternating currents are made to be continuous or to have the same direction. It may be attached to the end of the spindle of an electric motor, where a brush is in contact sequentially with the parts of the spindle that conduct current to the different windings of the motor.

Douglas Harper's Etymology Dictionary
commutator

1839, agent noun in Latin form from Latin commutare (see commute (v.)).

Wiktionary
commutator

n. 1 an electrical switch, in a generator or motor, that periodically reverses the direction of an electric current 2 (context mathematics English) (''of a group'') an element of the form ''ghg−1h−1'' where ''g'' and ''h'' are elements of the group; it is equal to the group's identity if and only if ''g'' and ''h'' commute 3 (context mathematics English) (''of a ring'') an element of the form ''ab-ba'', where ''a'' and ''b'' are elements of the ring, it is identical to the ring's zero element if and only if ''a'' and ''b'' commute

WordNet
commutator

n. switch for reversing the direction of an electric current

Wikipedia
Commutator

In mathematics, the commutator gives an indication of the extent to which a certain binary operation fails to be commutative. There are different definitions used in group theory and ring theory.

Commutator (electric)

thumb|upright=1.5|Commutator in a universal motor from a vacuum cleaner. Parts: (A) commutator, (B) brush, (C) rotor ( armature) windings, (D) stator (F) (field) windings, (E) brush guides

A commutator is a moving part of a rotary electrical switch in certain types of electric motors and electrical generators that periodically reverses the current direction between the rotor and the external circuit. It consists of a cylinder composed of multiple metal contact segments on the rotating armature of the machine. Two or more electrical contacts called " brushes" made of a soft conductive material like carbon press against the commutator, making sliding contact with successive segments of the commutator as it rotates. The windings (coils of wire) on the armature are connected to the commutator segments.

Commutators are used in direct current (DC) machines: dynamos (DC generators) and many DC motors as well as universal motors. In a motor the commutator applies electric current to the windings. By reversing the current direction in the rotating windings each half turn, a steady rotating force ( torque) is produced. In a generator the commutator picks off the current generated in the windings, reversing the direction of the current with each half turn, serving as a mechanical rectifier to convert the alternating current from the windings to unidirectional direct current in the external load circuit. The first direct current commutator-type machine, the dynamo, was built by Hippolyte Pixii in 1832, based on a suggestion by André-Marie Ampère.

Commutators are relatively inefficient, and also require periodic maintenance such as brush replacement. Therefore, commutated machines are declining in use, being replaced by alternating current (AC) machines, and in recent years by brushless DC motors which use semiconductor switches. __TOC__

Usage examples of "commutator".

It was in that city that I made a decided advance, which consisted in detaching the commutator from the machine and studying the phenomena in this new aspect, but still without result.

The consummation of the experiment was, however, delayed until the summer of that year, when I finally had the satisfaction of seeing the rotation effected by alternating currents of different phase, and without sliding contacts or commutator, as I had conceived a year before.

The call was done from the commutator of a hotel of Santa Lucia of the Sea.

Within the Sleeve were arrangements for coupling pipes and electrical cables via sliding ring joints and various commutator linkages, and for automatically moving cabs inward or outward between tubes terminating inside and outside the Sleeve.

Through an electrical arrangement involving rotating commutators, the proper sequence of pulses is sent out when a character's key is struck on the keyboard.

A line of fifty trucks from the Zenith Steel and Machinery Company was attacked by strikers-rushing out from the sidewalk, pulling drivers from the seats, smashing carburetors and commutators, while telephone girls cheered from the walk, and small boys heaved bricks.

It was in the second year of my studies that we received a Gramoe Dyname from Paris, having the horseshoe form of a laminated field magnet, and a wire wound armature with a commutator.