US789435A - Alternating-current dynamo-electric machine. - Google Patents

Description

No. 789,435. PATENTED MAY 9, 1905,

M. G. A. LATOUR.

ALTERNATING CURRENT DYNAMO ELECTRIC MACHINE:

APPLICATION FILED SEPT. 10, 1904.

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UNITED STATES Patented May 9, 1905.

PATENT OFFICE.

MARIUS O. A. LATOUR, OF PARIS, FRANCE, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

ALTE RNATlNG-CURRENT DYNAMO-ELECTRIC MACHINE.

SPECIFICATION forming part of Letters Patent No. 789,435, dated May 9, 1905,

Application filed September 10, 1904. Serial No. 223,941.

To a, whom, it may concern.-

Be it known that I, MARIUS CHARLES AR- THUR LATOUR, a citizen of France, residing at Paris, France, have invented certain new and useful Improvements in Alternating-Current Dynamo-Electric Machines, vof which the following is a specification.

My invention relates to alternating-current machines of the commutator type, and refers particularly to machines provided with what is known as a parallel or lap winding.

The object of my invention is to provide novel commutating means for such machines whereby sparking at the commutator is eliminated.

Commutation in alternating-current machines presents difiiculties which are absent in direct-current machines, since in an alternating-current machine the coil, which is shortcircuited at the instant of commutation, is subject to an alternating or pulsating field.

Various methods of reducing sparking have been devised; but by my invention 1 remove the cause of the sparking, since I arrange the commutator-brushes and their connections so that no coils are short-circuited within the machine during commutation. Furthermore, I do not accomplish this end by open-circuiting the armature, as has been done in some of the arrangements heretofore.

It is a evident that if a commutator is arranged with alternate live and dead segments of approximately equal width and if a single set of brushes bear on the commutator, each brush being of a width not greater than a single commutator-segment, then since a brush could not span two live segments no coil could be short-circuited during commutation. On the other hand, for the same reason the armature-circuit would be opened every time a brush was on a dead segment.

In machines for series or wave windings only a single pair of brushes is required for collecting the current for a multipolar machine, since all of the armature-winding is in series. 214,093, filed by me I have shown an arrangement which takes advantage of this characteristic of series-wound machines by providing In a former application, Serial No.

a commutator having alternate live and dead segments and employing a second set of brushes, each of a width no greater than that of a commutator-segment, placed like the first set at or near points of maximum potential, but on a different part of the commutator. By connecting the second set of brushes in parallel with the first and so arranging the second set that they are in engagement with live segments at the instant that the first set are in engagement with dead segments the armaturecircuit is maintained always closed, although the circuit of each brush is continually opened and closed. With this arrangement no short circuits occur within the machine, and since the only short circuits that can occur are those formed between the parallel connections of the brushes the flow of current may be readily controlled by resistances inserted in these connections and the amount of these resistances varied at will.

It is obvious that the above arrangement with a single commutator is not applicable to machines having parallel or lap windings, since with this latter type of winding a plurality of sets of brushes is always required, and the several portions of the armature-windings are connected in parallel instead of in series. Consequently if the same brush arrangement were used with a single commutator, as disclosed in my former application, the current-How through portions of the armature-winding would be interrupted whenever a set of brushes was on a dead segment. By providing two commutators. however, placed on opposite sides of the machine and connected to opposite sides of the armature-winding and by employing on each commutator the same number of brushes usually employed on the commutator of a parallel-wound machine with the same number of poles and by c0nnecting opposite brushes through resistances it is evident that the current-flow through the several portions of the armature-winding will never be interrupted, but will be merely shifted from one commutator to the other. Furthermore, it will be seen that only a length of active armature-winding corresponding with the active length of iron of the machine-or,

in other words, only a single conductorcan be at any time short-circuited, and since this short circuit is formed by the connection between corresponding brushes on the two commutators a resistance can be inserted in its connection and the amount of current-flow in the short circuit readily controlled.

My invention will best be understood by reference to the accompanying drawing, which shows somewhat diagrammatically a development on a plane surface of a parallel or lap winding for a four-pole machine provided with commutators and brushes in accordance with my invention.

In the drawing, A represents the armaturewinding, which is of the well-known lap or parallel type arranged for a four-pole machine, the position of the poles being inclieated by the shaded rectangles D. The two commutators G and C are placed on opposite sides of the armature-winding A, and each of these commutators is composed of alternate live and dead segments of approximately equal width, as disclosed in my former application above referred to. The dead segments may be made of insulating material or may be composed of conducting material simply insulated from the live segments. The live segments of each commutator are connected in the usual manner to the armature-winding, the segments of the two commutators being connected to opposite sides of the winding. Four pairs of brushes, 5 b to I! b, are placed on the commutators, one brush of each pair being on one commutator and each brush made with a width not greater than that of a single commutator-segment. Each brush 1) is connected to a brush 5 through a resistance R, and each brush 6 is connected with a brush I)" through a similar resistance It. The central point of the resistances R R are connected to each other, as are also the central points of the resistances R R It is evident from the drawing that no short circuit can be produced by a single brush, but that the only short circuits that can exist are through the connections of corresponding brushesas, for instance, between brushes 6 b It will be seen, however, that in passing from one brush to the corresponding brush of the same pair on the other commutator it is necessary to pass through one-half of each of two resistances. Consequently by properly proportioning the resistance the amount of shoi't-circuiting current may be kept within any desired limit, and, furthermore, the amount of this resistance, since it is external to the machine, may readily be controlled in amount manually or automatically during the operation of the machine. As has been said heretofore, the only short circuits existing in the machine are those formed by each pair of brushes and their connections. It will furrsaass thermore be seen that the portion of the winding short circuited between each pair of brushes is of a length equal only to the active length of the iron of the machine or, in other words, consists of a single conductor. The induced electromotive force in the short circuit is consequently very low and the external resistances may be made very small. Indeed, in small machines or machines of low voltage it will sometimes be found that the resistance of the two brushes alone is suflicient without the insertion of any additional resistance in the connection between them.

It will be understood that the drawing is a somewhat diagrammatic representation of the armature-winding and that I do not limit myself to the particular construction and arrangement of parts here shown, but aim in the appended claims to cover all modifications which are within the scope of my invention.

I/Vhat I claim as new, and desire to secure by Letters Patent of the United States, is

1. In an alternating-current dynamo-electric machine, a parallel or lap armature-winding, two commutators connected to said winding, and commutator-brushes and connections, so arranged that only a length of active winding equal to the active length of the iron of the machine is short-circuited in commutation.

2. In an altemating-current dynamo-electric machine, a parallel or lap armature-winding, two commutators on opposite sides of said winding, each commutator being composed of alternate live and dead segments and the live segments of each commutator being connected to the adjacent side of the armature-winding, and a set of brushes on each commutator, said sets being so arranged that a brush of one set is on a live segment when the corresponding brush of the other set is on a dead segment.

3. In an alternating-current dynamo-electria machine, a parallel or lap armature-winding, two commutators on opposite sides of said winding, each commutator being composed of alternate live and dead segments and the live segments of each commutator being connected to the adjacent side of the armature-winding, a set of brushes on each commutator, said sets being so arranged that a brush of one set is on a live segment when the corresponding brush of the other set is on a dead segment, electrical connections between corresponding brushes of said two sets, and resistances inserted in said connections.

In witness whereof I have hereunto set my hand this 8th day of September, 190st.

MARIUS C. A. LA OUR.

Vvitnesses:

G. (J. I'IOLLIS'IER, HELEN ()RFORD.

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