commutator


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commutator,

device used in an electric generatorgenerator,
in electricity, machine used to change mechanical energy into electrical energy. It operates on the principle of electromagnetic induction, discovered (1831) by Michael Faraday.
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 to convert the alternating current produced in the generator into direct current before the current is sent into an external circuit; it is basically a rotary switching device synchronized with the frequency of the alternating current. Commutators are also used in electric motorsmotor, electric,
machine that converts electrical energy into mechanical energy. When an electric current is passed through a wire loop that is in a magnetic field, the loop will rotate and the rotating motion is transmitted to a shaft, providing useful mechanical work.
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 to switch currents in order to maintain magnetic polarities necessary to keep the shafts of the motors turning.

Commutator

 

in electrical machinery, a mechanical frequency converter that is attached to the rotor of a machine. A commutator consists of a series of trapezoidal copper segments that are insulated from each other and from the body of the rotor. Each segment is connected to one or more turns of the armature winding. The armature winding is connected to an outside power source by carbon contact brushes. When the armature rotates, the brushes touch each of the commutator segments in turn.

The most common type of commutator is the cylindrical type, with brushes contacting the outer surface. Disk commutators, whose work (contact) surface is perpendicular to the axis of rotation of the rotor, are less frequently used. The commutator segments in low-powered machines (up to 10 kilowatts [kW]) are pressed into plastics; in machines with power ratings of 15–25 kW or more and a speed of rotation of 3,000 rpm or higher, the segments are fastened by steel tread rings. In large electric machines double or triple commutators are sometimes used to reduce mechanical stresses. The disadvantages of commutators are high consumption of electrical-grade copper, sparking, and wear caused by brush friction.

REFERENCES

Petrov, G. N. Elektricheskie mashiny, 2nd ed., part 3. Moscow, 1968.
Vazhnov, A. I. Elektricheskie mashiny. Leningrad, 1969.

V. V. BOGOMAZOV

commutator

[′käm·yə‚tād·ər]
(electromagnetism)
That part of a direct-current motor or generator which serves the dual function, in combination with brushes, of providing an electrical connection between the rotating armature winding and the stationary terminals, and of permitting reversal of the current in the armature windings.
(mathematics)
The commutator of a and b is the element c of a group such that bac = ab.
(quantum mechanics)
The commutator of a and b is [a,b ] = ab-ba.

commutator

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
References in periodicals archive ?
For any differential l-form u(x), by the definition of commutator of Calderon-Zygmund singular integral operator on differential forms, we have
Since [DELTA](g) = g [cross product] g, we find that the definition of the commutator given in (4), boils down to the group commutator [a,b] = ab[a.sup.-1][b.sup.-1] for all a, b [member of] G.
We shall represent an expression, describing cutting force when turning the intermittent commutator surface, as:
Now assume that [gamma] is not a subset of the contacts of [LAMBDA]', and consider any commutator of [gamma] which is not a contact of [LAMBDA]'.
Our analysis also leads naturally to a modification of the LSC preconditioner that emphasizes important relationships for components of the commutator associated with boundaries.
This design uses specially formulated graphite that is molded directly into and around the commutator body, producing a secure assembly without solder or adhesives.
Regarding the first order commutator [C.sub.b] as an operator acting on [A.sub.[alpha]], we have [C.sub.b] = (I - [P.sub.alpha])[M.sub.b][P.sub.[alpha]] = [H.sub.b] on [A.sub.[alpha]], where [H.sub.b] : [A.sub.[alpha]] [right arrow] [([A.sub.[alpha]]).sup.[perpendicular to]] is known as the Hankel operator with symbol b.
Current is conducted by carbon brushes to copper commutator bars mounted to an armature that also has field windings.
newman's machine consists of a battery pack, a commutator connected to a rotating permanent magnet and a coil of wire.
Contract Awarded for Design,supply,installation,foundation & other civil works, testing, commissioning and proving of Commutator TIG Welding Machine (Horizontal Type), IGBT inverter based AC- DC for TIG Welding to copper and its alloy of the commutators riser with power coils and equalizers coils leads of TM 4907, TM 4303, TM 4601, Hitachi HS 15250A armatures as per specification including comprehensive (preventive & Breakdown) maintenance and AMC for setting up the second electric loco shed at Bondamunda of South Eastern Railway.
If power supply connected with magnetic field winding of DC Machine and rotor of the machine is turned by an external source of mechanical power, then a voltage will be induced in conductor of rotor, this voltage will be rectified in DC output by using machine's commutator, a magnetic field will produce around it which will disturb the original magnetic field from the poles this distortion of flux in DC machine is called Armature Reaction.
Let T be a linear operator in a measurable function space; then, the commutator formed by T and b [member of] [L.sub.loc]([R.sup.n]) is defined by