US837425A - Commutator. - Google Patents

Description

PATENTED DEC. 4, 19 06.

S. S. SEYFBRT. GOMMUTAT OR.

APPLICATION FILED 133.20, 1905.

3 SHEETS-SHEET l.

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'PATENTED 1130.4, 1906.

S. S. SEYFBRT. COMMUTATOR.

APPLICATION FILED rm. 20, 1905.

3 SHEETS-SHEET 2.

S. S. SEYFERT.

GOMMUTATOR.

AP PLIOATION FILED FEB. 20, 1905.

3 SHEETS-SHEET 3.

PATEVNTED DEC. 4, 1906.

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UNITED STATES PATENT OFFIOE.

STANLEY S. SEYFERT, OF SOUTH BETHLEHEM, PENNSYLVANIA, ASSIGNOR OF ONE-HALF TO WILLIAM S. FRANKLIN, OF SOUTH BETHLEHEM,

PENNSYLVANIA.

'COMMUTATIQR.

Specification of Letters Patent.

Patented. Dec. 4, 1906.

, Application filed February 20, 1905. Serial No. 246.587.

and a longitudinal sectional view of a corn mutator embodying my invention, and Figs. 5 and 6 are views similar to Figs. 4 and 5 of another-embodiment of my invention.

The object of my invention has been to provide a commutator by which currents of high voltages can be commutated without sparking, such commutator, while especially valuable in alternating-current motors, being I adapted for use in commutating other ourby the brushes is the seat of a comparatively rents than those in a motor; and to such ends my invention consists in the commutator hereinafter specified.

The, commutators of all single-phase motors at present devised other than that here-- inafter described are, so far as I am aware, so constructed as to be subject to such serious sparking at the brushes as to prevent the use of currents ateconomical voltages. The main cause of sparking is the fact that the coil of the armature which is short-circuited high electromotive force induced in it b y transformer action, because of the alternating character of the exciting-field. Such coil is perpendicular to the lines of force and is therefore in position to embrace the largest possible number of lines of force, so that the inductive action therein is the strongest possible in any coil of the armature.

Such coil being short-circuited by the brushes, large currents will flow in it, because of the comparatively low resistance of the short-circuit path. These currents causeheating of the brush-contacts, a loss of power, and sparks when the short-circuit is broken. The object of the commutator about to be described.

is to reduce such short-circuit currents, and thus to save power and minimize the destructive heating and sparking at the commutator.

The commutator is diagrammatically illustrated in Fig. 1, in which the coils on sections A A, &c., of the armature-winding are connected by leads B B, &c., which would ordinarily pass directlyto the commutator-segments, but which in accordance with my 1n-' vention are connected with choke-coils O C, &c., and D D, &c., in airs, the choke-coils being connected by lea s E E, &c., with the commutator-segments F F, &c. The choke or inductance coils C &c. and D, &c. are so arranged that when alternating current flows upward or downward in both coils of a pair their magnetizing action will be equal and 01pposite, and no impedance will be offered to t passage of the current. If, however, current tries to flow up one coil and down the adjacent coil of a given pair, such as up one coil C and down the adjacent coil D, the magnetizing action of the two coils will be in the same direction, and a heavy impedancewill be opposed to such current. For this urpose two choke-coils may be wound on t e same iron core or magnetic circuit, and the termi-. nals are connected so as to obtain the efiect above mentioned. Thus coils C and D are linked with-one 'ma netic circuit, while coils C and D are linke with another magnetic circuit, and soon. In the operation of my commutator, as illustrated in Fig. 1, at the instant when the brush G bridges over the segments F and F if transformer electromotive forces are introduced in coil A they will tend to produce corresponding currents in the short-circuit, which may be assumed to be in the direction of the dotted arrow below such coil at a given instant. Then current will tend to flow down the lead 13, down coil C ,-dOWI1 lead E through commutator-segment F through the brush G to the segment F, and thence through lead E and 0011 D andback to the armature-coil by lead B It will thus be seen that this short circuit current must flow down coil C and up coil D but, as before stated, when this takes place the coils interpose a lar e choking ef: feet, and hence the short-circuit current will be kept down on account of the inductance of the coils C and D 'While the coils C and D will largely prevent the flow of current formed by transformer action in the short,- circuited coil, they do not ofier any objec- 'tionable resistance to the flow of the main armature-current, because such current will pass through both of such coils in the same direction-that is, upward or downward, so that their magnetizing action will be coun' terbalanced. No substantial portion of the short-circuit current above described can flow in the isolated coils D and 0 because their magnetizing action is not counterbal- 'anced b any 0 posite magnetizing action,

and suc coils t erefore offer their full impedance to the passa e of current.

Continuing now t e theory of my commutator, if a number of commutator-segments between a set of positive and negative brushes be, say, fifty, then each of the chokecoils, as above described, will be actuallycarrying half of the armature-current for only about one twenty-fifth of the time. If be half the armature-current (assuming bipolar, simplex, la -winding) and R be the resistance of a cho e- ,coil, then while current is actually flowing the rate of heat-generation in the coil under consideration is R(%-) but since this occurs only one tw'entyfifth of the time the actual rate of heat generation may be twenty-five times as great while it occurs and still not heat the choke-coils faster than the armature is being heatedthat is, the resistance of the choke-coil may be twenty-five times as great as would be permissible if the current were flowing all the time, or the cross-section of the conductors of the choke-coils may be made one twentyfifth of the cross-section of the armatureconductors, keeping their length the same. The same eflect can be obtained by multiplyin the length of the choke-coils by five and ecreasing their cross-section to onefifth, thus givin approximately five times as many turns and twenty-five times as much an inductance in a given space: Thus it happens that the resistance of two of these 0110 -coils in serieswill be considerable, and this still further tends to reduce the shortcircuit current. spect to the main-armature current, the two coils C and D, Fig. 1, are in parallel and their combinedresistance will still be small as com ared to the total armature-resistance. thus obtain the efiect of the introduction of ohmic resistance in the short-circuit formed by the bridging of two commutator-segments by a brush; but I do so without'requiring the use of high-resistance material, inasmuch as my choke-coils may be of good copper wire, but of greatly diminished cross-section .and greater length as compared with the conductor of the armature.

thus obtain the double'object of introducing high resistance in the short-circuit, together with the choking effect of'the coils thus formed, without introducing an objectionable bulk of material. If the inductancecoils were formed of material of high ohmic I resistance and a sufficient length were used .-commutator-segm'ents.

On the other hand, with reto produce the desired inductive effect, a bulk would result that would be a serious objection.

The choke-coils may be of copper strap insulated with asbestos, so as to be thoroughly heat-proof.

It will be seen that with-my commutator the simplest form of armature-winding may be used and no special form of brushes is required. A higher voltage per segment can also be used, giving either a higher line voltage or a lower ratio of transformation. j

The commutator may be varied in form. In Fig. 2 is illustrated diagrammatically an arrangement of commutator on the principle of that illustrated in Fig. 1;, in which compactness and economy of iron is effected.

The armature coils H H, &c., are, as before,

connected by leads I I, &c., with chokecoils K K, &c., and L L, &c., the latter being wound on the multiple iron core M. This core may consist of a ring or band of iron laminations with openings punched in the same for receiving the coils. The coils are connected by leads N N, &c., with commutator-segments O O, &c., that coact with the brush P.

In Figs. 3 and 4 is illustrated a commutator constructed according to the arrangement illustrated in Fig. 2 and applied to a railway-motor.

The case Q .is provided with a cover R, in which is formed a bearing for the shaft S. The commutator-segments T are held between two annular plates U and U, respectively, the plates having flanges a and a, respectively, which bear against the inner surface of the motor-casing. The plates are clamped against opposite sides of the commutator-segments by bolts V, the plates having V-shape ribs W, which. engage complemental recesses formed in the The ring of commutator-segments is thus made stationary. The inner surface of the segment-ring is used for contact with the brushes X, and the latter are mounted in brush-holders Y, hav ing stems y, that are secured by .nuts to a carrier Z, that is mounted on and rotates with the shaft. The brush-holders are insulated from the carrier and the connections with the brushes are made to the brushholders. Between the plates U and U the choke-coils A and their core B are mounted. The core is annular in form, as illustrated in Fig. 4, and it is preferably laminated. The core is provided with slots parallel to but removed from its outer periphery, and the choke-coils are wound through such slots. The coils are, as indicated in Fig. 2, connected with the commutator-segments and with the armature-coils. The coils are most conveniently formed of strap conductor, althou h wire can be used.-

'lnFigs. 5 and'6 is illustrated a commutator constructed according to the arrange- The choke-coils are connected by leads U" with the armature-coils. The electrical ac- 'tion of the commutator illustrated in Figs.

and 6 is the same as that illustrated in Figs.

3 and 4.

My commutator has, among others, the

following advantages: r

The commutator, being stationary, may

be constructed very rigidly and is better suited to radiate heat than the ordinary commutator. This is an important factor, as the commutator of an alternating-current motor has an especial tendency to heat on account of the short-circuited current under the brushes. The stationary commutator allows of a great subdivision of poles, and hence less trouble with short-circuit voltages under the brushes (because the flux per pole need notbe-as great; and hence less voltage produced per coil).

It being practicable to use a material of good conductivity, such as copper, in the chokecoils and still to obtain the desired resistance, the cost is less than if it were necessary, as heretofore, to use a material of poor conductivity, such as German silver.

The commutator-segment rin being eX- ternal ermits the core of the cho e-coils and the coi s themselves to be as large as desired.

The use of an external segment-ring affords room within the ring for. the shaftbearing, thus saving the space on the shaft which would be taken up if the bearing were beyond the side face of the segment-ring 'as heretofore constructed. This is an important consideration Where the space is limited,

' as in railway-motors.

It is obvious that various changes can be made in the above-illustrated construction which will be within the scope of my invention.

/ Having thus described my invention, what I claim is a v 1. In an electrical device, the combination of an armature comprising coils, a commutator comprising segments, leads connecting said coils and segments, and oppositely act ing inductances ineach lead, the inductances of o posite signs in different leads being situate in the same magnetic circuit.

2. In an electrical device, the combination of an armature comprising coils, a commu tator comprising segments,,leads connecting said coils and segments, and oppositely-acting inductances in each lead, the inductances of opposite signs in difierent leads being situated in the same magnetic circuit, said 'in, ductances being composed of material of high conductivity.

3. In an electrical device, the combination of an armature comprising coils, and a commutator comprising segments, of inductive resistance connected in the leads, assing from said coils to said segments, sai resistance being active as against current tending to form by short-circuiting a coil and being passive as against the main armature-current.

4. In an electrical device, the combination of an armature comprising coils, a commutator comprising segments, and ohmic and. inductive resistance connected in the leads passing from said coils to said segments, said resistance being of high conductivity, being active as against current tending to form by short-circuiting a coil, and being passive as against the main armature-current.

5. In an electrical device, the combination of an armature comprising coils, a commutator com rising segments, and oppositelywound in uctance-coils connected in each lead from said armature-coils to said segments, oppositely-wound'coils of adjacent leads having a common magnetic circuit.

6. In an electrical device, the combination of-an armature comprising coils, a commutator comprising segments, and oppositely wound inductance-coils connected in each lead between said armature-coils and said segments, oppositely-Wound coils of adjacent leads having a common core and a common magnetic circuit, all of said cores forming parts of a single mass of iron. 4

7. In an electrical device, the combination of an armature comprising coils, a commusteel having slots formed parallel to, but removed from, its periphery, said coils being wound through said slots.

8. In an electrical device, the combination of an armature comprising coils, a commutator comprising segments, and oppositelywound inductance-coils connected in pairs in the leads passing from said coils to said segments, each of said pairs of coils being wound upon a core common to said pair, all of said cores forming parts of a single mass of iron or;

steel, said mass comprising a r ng or rings 'of' steel having slots formed parallel to, but removed from, its periphery, said coils being- Wound through said slots, and over said periphery. v

9. In an electrical device, thecombination' of an armature comprising coils, a commutator com rising segments, and oppositelywoundin uctance-coils connected in pairs 1n.

the leads passing from said coils to said segments, each of said pairs of coils being Wound upona core common to said pair, all oi-said cores forrning parts of a single mass of iron or steel, said. mass comprising a ring or rings of steel having slots formed parallel to, but removed from, its periphery, said coils being Wound through said slots and over said periphery, said coils being formed of bands of metal of high conductivity.

10. In an electrical device, the combination of an armature comprising coils, a commutator comprising segments, and. oppositely-Wound inductance-coils connected in pairs in the leads passing from said coils to said segments, each of said pairs oi coils hesenses ing Wound upon a core common to.said pair, all of said cores forming parts of a single mass of iron or steel, said mass comprising a ring or rings of steel having slots formed parallel to, but removed from, its periphery, said coils being wound through said slots and over said periphery, said coils being formed of bands of metal of high conductivity, said bands being insulated with non-combustible material.

In testimony that I claim the foregoing I have hereunto set my hand.

STANLEY, S. SEYFERT. Witnesses:

NILLiAM S. FRANKLIN, A. L. Core.

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