US2550574A - Commutator construction - Google Patents

Description

April 24, 1951 c. LYNN COMMUTATOR CONSTRUCTION Filed Jan. 10, 1950 INVENTOR Cldrence Lynn. avra & e

ATTORNEY Patented Apr. 24, 1951 COMMUTATOR CONSTRUCTION Clarence Lynn, Pittsburgh, Pa., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application January 10, 1950, Serial No. 137,'710 6 Claims. (ol. 171 321) My invention relates to commutator-type rotormembers of dynamo-electric machines, and it has particular relation to the kind of commutators which are used in high-speed, direct-driven, turbo-generator exciters.

In commutator-constructions of the type to which my invention relates, the commutatornecks are thinner, circumferentially, than the commutator bars. In order to prevent dirt-laden air from passing back through the spaces between the commutator-necks, and depositing a layer of electrically oonducting dirt underneath the coil-ends of the armature-winding, and ultimately providing a short-circuiting path of relatively high resistance to ground, it has been customary to fill the space under the coil-ends, between the commutator-necks and the front end of the rotor-core, and also the circumferential spaces between the commutator-nccks, with a heat-hardening asbestos filling-compound or cement. This expeclient has been practiced for some time, because of the urgency of the necessity for preventing conducting deposits from forming back of the commutator-necks, notwithstanding the fact that it has resulted in a considerable increase in the temperature of the commutator. In some cases, this has presented a considerable problem in keeping the temperature-rise to the guaranteed 55 at rated loadconditions i It is an. object of my present invention to overcome the excessive-temperature difficulty by filling only the back portions of the circumferential spaces between the commutator-necks, leaving substantially large unfilled spaces between the front porticns of the oommutator-necks, thus causing said front portions of the necks to act as fan-blades and as heat-radiatng surfaces for conducting heat away from the commutator-bars. In one instance, this expedient has resulted in as much as an l8 reduction in the commutatortemperature. In the high-speed machines to which my invention is more particularly applicable, it is necessary or desirable to use banding around the commutator-nccks, in order to restrain them against centriiugal force, and when my present invention is used, this banding is applied only over the filled rear portions of the commutator-necks In commutator-constructions of the type having solid necks, or necks which are thick in a circumierential direction, so that there is substantially no space between adj acent necks, it has been custcmary, heretofore, to use a filling-cement or compound back of the necks, and underneath the coil-ends of the armature-winding, butthese constructions have lacked the spaced thin front neck-portions which act as fan-blades and heat-dissipating surfaces in accordance with my invention.

With the foregoing and other objects in view,

my invention consists in the structures, combi-.

nations, parts, and methods of design and operation, hereinafter described, claimed and illustrated in the accompanying drawing, wherein:

Figure 1 is a fragmentary longitudinal section of a portion of a dynamo-electrc machine, illustrating my invention, the section-plane being indicated by the broken line I-I in Fig. 3;

Fig. 2 is a fragmentary transverse sectional View along the line II-II in Fig. 1, with a portion of the figure broken back to show a section along the line IIa-IIa of Fig. 2, and

Fig. 3 is a ragmentary cylindrical section on the line III- III of Figs. 1 and 2.

I show my invention applied to a dynamo-electrio machine having a stator-member I and a' rotor-member 2. The rotor 2 has a core 3 mounted on a shaft 4. spaced axially from the e front end of the rotor-core, is a commutator',

which is illustrated as comprising a plurality of commutator-bars 6 and mica bars 6' (Figs. 2 and 3), which are held in place by a shrink-ring T (Fig. 1), which is centered and supported within a centering-plate 8. The centering-plate 8 is supported on a commutator-bush or shell 9, which is mounted on the shaft 4, in accordance with a known Construction. The centerng-plate 8 also has a portion extending radially outwardly far enough to constitute a coil-support o.

The commutator 5 is also provided with a plurality of commutator-necks IG which are thinner, circumferentially, than the bars 6, said commutator-necks being set into, and securely fastened within, suitable saw-outs IT (Figs. 1 and 2) a in the respective bars, in accordance with a known mutator-necks 16 and the front end of the rotorcore, construing the insulating-pad 23 and the centering-plate 8 (when used) as constituting the front end of the core-Construction 3. 'I'he idea is, to fill the space underneath the coil-ends l8, so that no conducting deposit may be carried there by the ventilating-air. The insulating pad 23 is used between the two layers of the front end-windings of the armature, in the case of a two-layer armature-winding.

In the particular illustrated form of my invention which is shown in the drawing, I preferably use a plurality of neck-wedges 22 which are made of solid insulating material, and which are disposed between the rear portions of the circumferential spaces between the commutatornecks 16, thus leaving substantially large unfilled spaces 24 between the front portions of the commutator-necks. In the particular form of embodiment which is shown in the drawing, the coil-ends |8 are disposed at one side of the respective necks l6 to which they are attached, and the respective neck-wedges 22 are disposed between the other sides of these coil-ends !8, and the other side of the next adjacent'neck 15, leaving spaces 25, under the coil-ends 58. These spaces 25 are also filled with cement 2l.

In operation, the essential feature of my invention is that the necks IS' shall be 'thinner, circumferentially, than the commutator-bars E, so that there is a circumferential spacing between successive necks. The rear halves, orother suitable portion, of this between-neck spacing is filled' by a suitable filling, which is generically indicated at 28 in the drawing, and which may consist of cement alone, or suitably fitted neckwedges alone, or, :as shown, partly cement and partly the neck-wedges. It is important that the front spaces 24' should be left unfilled, occupying the front half-inch, or other substantially large portion, of the' spaces between the successive necks.

In the particular form of invention which is illustrated in' the drawing, the neck-wedges 22 are wide enough, in an axial direction, to extend backwardly for about a quarter of an inch behind the rear ends of the eommutator-necks IS, and these rearwardly extendingportions of 'the wedges 22 are provided with vertical grooves 26, 01' other 'means for providing shoulders 21 (Fig. 3) for `interlocking engagement with the filling-compound 2|, so that the filling-compound helps to hold the wedges'in place.

When my invention is applied to high-speed machines, such as turbo-exciters, it is necessary, or quite desirable, to use banding 28, both over the coiI-ends IS, and over the rear filled portions of the spaces between the commutator-necks !6, but this banding should not eXtend over the front unfilled spaces 24`between the necks. The banding thus serves to retain both the necks !5, and the neck-we'dges 22, against centrifugal force. At the same time, the banding does not extend forward far enough to interfere with the radial air-flow which is induced by the spaced front halves of the necks l 6.

Experience has shown that my invention results in just as good prevention of short-circuiting deposits by the dustand dirt-laden ventilatingair, as in the previously used constructions. The banding which extends over the rear halves of the necks adequately retains the necks against centrifugal force, and when my neek-wedges 22 are used, this banding also adequately retains the wedges against centrifugal force. At the same time, the omission of the banding over the unfilled front spaces 24 between the commutatornecks, leaves an unimpeded path for the free radial blast of ventilating-air, which is produced by the fan-blade action of the front halves of the necks. In one particular instance, the introduction of my invention produced a commutator having a temperature-rise of 43 C., which is 12 below the usual guarantee, whereas, with the old form of Construction, without the unfilled substantially large front spaces 24, the temperaturerise was 61, or 6 over the guaranteed temperature-rise.

While I have illustrated and `described my invention in a single form of embodiment, which is at present preferred, it will be obvious that my invention is susceptible of considerable Variation, by way of additions, omissions and the substitution of equivalents, without departing from the essential 'spirit of the invention. I desire, therefore, that the appended claims shall be accorded the broadest Construction consistent with their language.

I claim as my invention:

1. A commutator-type dynamo-electric machine having a rotor-core, an armature-winding carried by the rotor-core, a commutator spaced axially from the front end of the rotor-core, said commutator comprising a plurality of commutator-bars, and commutator-necks which are thinner, circum'ferentially, than the bars, said commutator-ne'cks being set into, and securely fastened to, the respective bars, electrical connections'between the commutator-necks and the coilends of the armature-winding, and a filling including a hardenable insulatng filling-compound, said filling occupying the space under the coilends, between the commutator-necks and the front end of the rotor-core, and also filling the rear portions of the circumferential spaces between the commutator-necks, leaving substantially large unfilled spaces between the front portions of the commutator-necks.

2. The invention as defined in claim 1, characterized by said filling comprising also solid neckwedges disposed between said rear portions of the commutator-necks.

3. The invention as defined in claim 1, characterized by said filling comprising solid neckwedges disposed between said rear portions of the commutator-necks, said neck-wedges extending to the rear of said =commutator-necks and having shoulder-portions for interlocking engagement with said 'filling-compound.

4. The invention asdefined in claim 1, in combinaton with banding around said coil-ends and around said filled portions, but not around the unfilled portions, of the commutator-necks.

5a The invention as defined in claim 1, in combination with banding around said coil-ends and around-said filled portions, but not around the unfilled portions, of the commutator-necks, said filling comprising also solid neck-wedges disposed between said rear portions of the commutator-necks.

G. The invention as defined in claim 1, in combination with banding aroundsaid coil-ends and around said filled portions, but not around the unfilled portions, of the commutator-necks, said filling comprising solid neck-wedges disposed between said rear portions of the commutatornecks, said neck-wedges extending to the rear of said commutator-necks and having shoulderportions for interlocking engagement with said filling-compound. I

CLARENCE LYNN BEFERENCES CITED UNITED STATES PATENTS Name Date Edison Oct. 20, 1885 Number

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