US920626A - Dynamo-electric machine. - Google Patents

Description

I Patented May 4, 1909 H RM um. T m EE VU NN E U M J ATTY.

GGERATH.

DYNAMO TRIC MACHINE. APPLICATION FILED JULY NOE ELEG

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UTTEB STATES PATENT OFFIQE.

JAKOB E. NOEGGERATH, OF SGHENEOTADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

DYNAMO-ELEC'IRIC MACHINE Specification of Letters Patent.

Patented May 4, 1909.

Application filed Ju1y'23, 1908. Serial No. 444,881.

big speeds. Furthermore, a comparatively large number of brushes must be employed to collect the current induced in the armature. If readily volatilized metal were used for collector-rings or brushes, the wear on this large number of brushes would be great. I, consequently, prefer, as disclosed in prior applications, to employ collector-rings of metal which does not readily volatilize, as, for instance, steel, with brushes composed partly of similar metal and partly of hi hly conducting metal such as copper. These brushes may be .constructedof laminae, partly of copper and partly of steel. The copper laminae give the brushes high conductivity, while the steel laminae reduce they wear on the brushes.

I have discovered that if the collectorrings are made of steel and-thebrushes are partly composed of steel laminae, a very considerable stray flux asses through the collector-rings and brus es due to the compare tively 10W magnetic reluctance of this path.

' brush; and consequently Tl'fis flux shifts its position in the collectorrings, as the armature revolves and diilerent parts of the ring are bropght beneath the dy-currents are induced in the collector-rings, which result in heating losses materially affecting the efficiency of the machine.

One feature of my invention consists in providing means for preventing or reducing the stray flux, which produces these losses. I accomplish this by providing coils arranged magnetic material in the path of the flux to produce a magnetomotive force opposing a stray .flux assing through collector-ring and brush. acli coil may surround the ath of the stray flux through a number of lirushes, or each coil may surround a single brush.

; As a further means of reducing stray fluxes andresultant licating losses, I introduce nonunilpolar machines, they must bedriven atpassing through collector-ring and brush. To reduce the eddy current losses in the collector rings due to the reversal of current in them as they pass under the brushes, which losses would otherwise be appreciable because the rings are of magnetic material, I provide the rings with a strip of hi hly conducting material such as copper, which carries most of the current and is shaped so that the flux in the collector ring is made comparatively small.

A further feature of my invention consists in so distributing the volatile and non-volatile material in the brushes as to obtain a more even wear, than would be the case if all the brushes were similarly constructed. For a given brush'construction, the amount of wear varies according to the polarity of the brush, the wear being greater where the current flows from brush to ring. The wear is thus greater at the negative brushes of a genorator and-at the ositive brushes of a motor. I according y form those brushes, through which current flows to the collectorrings, with a greater proportion ofsteel and a smaller proportion of copper than the brushes at the'other end the machine.

My invention will best be understood by reference to the accompanying drawings, in which Figure '1 shows a portion of a unipolar machine havin a coil for o posing a stray flux. through 1; e brushes; 1g. 2 shows a modified structure of the coil; Fig. 3 shows diagrammatically the differently constructed brushes at opposite ends of the machine; Figs. 4 and 5 are cross-sections of the col lector-rings on the lines 4-4 and 5-5 of Fig. 1, respectively; and Figs. 6, 7 and 8 show modified constructions.

Inthe drawings, A represents a collectorring, which is supported on the armature periphery (not shown) by studs (1 a.

B represents brushes bearing on the collector-rlng. These brushes are carried by brush-holders C, which extend through apertures in the field magnet D, which apertures are provided to ailord easy access to the brushes. It willbe seen from Fig. 1

that if the collector-ring is of steel, the

brushes B com osed partly of steel lamina, and the brush olders O of magnetic material, t a path of comparatively low reluctance is affordedthrough collector-ring and brushes for a stray flux passing from the armature'to thefieldmagnet, and that this Itis not necessary that the coils for opposing the stray flux should each surround a plurality of brushes; instead, coils e may be employed as shown in Fig. 2, each surrounding a single brush. It has been said" that the brushes are composed of copper and steel laminae. I have also said that it is desirable to employ a greater proportion of steel in those brushes from which current fldws to the collector-ring. Such an arrangement is indicated diagrammatically in Fig. 3, in which E represents an armature conductor connected at its opposite ends to, collector-rings. The direction of current in the conductor is indicated by anarrow, and also b the plus and minus signs applied to the co lector-rings. The copper laminae are indicated by b and the steel laminae by b. It will beseen that the brush in engagement with the negative collector-ring is composed more largely of "steel than the other brush.

. By this difference in their material, the wear on ghe two brushes is approximately equal ize In addition to, or in lace of, the coils for opposing a stray flux t rough the brushes,

non-magnetic material may be introduced in the path of this stray flux. This may take the form of non-magnetic supporting studs 0,, for the collector-rings and co per strips F sheathing the inner periphery o the rings.

These strips also reduce the losses due to eddy currents produced in the rings by reversal of current therein under the brushes, since the strips, being of high conductivity, carry most of the current and may' be so shaped as to give a long path in air g t any flux surrounding the strip, so that the amount of flux in the collector rings is made comparatively small. Suitable shapes for the strips are indicated in Figs. 6, and 8. In Fig. 6 the width of the strip F 1s innot bent down.

creased, and its edges bent down to form flanges extending away from the collector.- ring so that the path in air of a flux surrounding the strip is comparatively long. In Fig. 7 the strip F is widened, but its edges are In Fig. 8 the strip is widened and also has a depending central flange. Since these strips greatly reduce the flux in the collector-rings, they greatly reduce the eddy current losses due to current reversal .in the rings.

I do not desire to limit myself to" the particular construction and arrangement of parts here shown,fbut aim in the a 'nded Within the scope of my invention. i

What I claim as new and desire to secure byLetters Patent of the United States, is,

-1. In a d amo-electric machine, collec: tor-rings an brushes both having ma etic material in their composition, and co arranged to produce a magnetomotive force opposing a stray flux passing through collector-rings and brushes.

2. In a d amo-electric machine, collector-rings an brushes both havin magnetic material in their composition, anfi coils surrounding the path 0 a stray flux passing throu h said brushes. 3. In a dynamo-electric machine, collector-rings of magnetic material, a magnetic field structure provided with apertures, brush-holders extending through said a ertures, brushes having ma etic materi in their composition carrie by said brush holders and engaging said collector-' s,

and coils surrounding said apertures on t e "claimsto cover all modifications w 1chtfgare' doctors having a greater proportion of hard metal'than the brushes at the other end.

5. In a dynamo-electric machine, armature conductors connected at both ends to collector-rings, and brushes engaging said rings composed of laminae of hard and soft metals, the hard metal laminae composing a greater part of the brushes at one end of the conductors than of the brushes at the other 6. In a dynamo-electric machine, collector-rings and brushes both having magnetic material in their composition, and members of nonmagneti'c 5 material inserted in the ath of a stray flux passing through rings and rushes.

7. In. a dynamo-electric machine, collec- I tor-ringsancl brushesboth having magnetic a material in their composition, and highly conducting members of non-magnetic material inserted in the path of a stray flux passing through said rings.

8. In a dynamo-electric machine, collector-rings and brushes both-having magnetic material in their composition, and a sheathing of highly conductin non-magnetic material on the inner side 0 said rings.

9. In a dynamo-electric machine, collector-rings ha ving magnetic material in their I rings shaped to' give a, long Fath through air composition, and strips of highly conductin for a flux surrounding one 0 said strips. 10 non-magnetic material in contact with sai( In witness whereof, I have hereunto set my rings. 1 hand this 21st dag of July, 1908. 0 10. In a dynamo-electric machine, collec- JAK B NOEGGERATH.

tor-rings having magnetic material in their Witnesses: composition, and strips of highly conductin BENJAMIN B. HULL, non-magnetic material in contact with sai HELEN ORFORD.

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