US804440A - Dynamo-electric machine. - Google Patents

Description

No. 804,440. PATENTED NOV. 14, 1905. 0. P. STEINMETZ.

DYNAMO ELECTRIC MACHINE.

APPLICATION FILED APR.22,1904.

2 SHEETS-SHEET l.

Witnesses- Inventor":

Charles I? Steinynetz.

PATENTED NOV. 14, 1905.

C. P. STEINMETZ.

DYNAMO ELECTRIC MACHINE.

APPLICATION FILED APR,22.1904.

2 SHEETS-SHEET Z.

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.u t e ww M8! 6 V 2W 0 N QUU i040 C Witnesses- UNITED STATES PATENT OFFICE.

CHARLES P. STEINMETZ, OF SCHENECTADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

DYNAMO-ELECTRIC MACHINE.

Specification of Letters Patent.

Patented Nov. 14, 1905.

Application filed April 22, 19,04. Serial No. 204,315.

To all whom, it may concern.-

Be it known that I, CHARLES P. STEINMETZ, a citizen of the United States, residing at Schenectady, in the county of Schenectady and State of New York, have invented certain new and useful Improvements in Dynamo-Electric Machines, of which the following is a specification.

My invention relates to dynamo electric machines of the type known as homopolar. These machines, as ordinarily constructed heretofore, have been subject to two objections which have prevented them from coming into general commercial use. In the first place the structure of the machine, which consists of a conductor or conductors rotating in a uniform field with means for leading oif the current from the ends of the conductors, renders it impossible to employ a winding comprising a plurality of conductors wound in series, as in direct-current machines of the commutator type. In order to obtain a terminal voltage in a homopolar machine greater than the induced potential in a single conductor, it is necessary to provide each conductor with a pair of collector-rings and connect the collector-rings in series by means of brushes and external connections. With machines running at speeds which have been customary heretofore it is impossible to obtain a sufficiently high voltage for many commercial purposes without resorting to a prohibitive number of collector-rings. This constitutes the first difiiculty which has hitherto stood in the way of the general use of homopolar machines. The second difliculty lies in the great armature reaction inherent in machines of this type as heretofore constructed. This reaction produces such a drop of voltage under load as to render such machines wholly unsuitable for work in which a constant potential is required.

The use of steam-turbines as prime movers is rapidly removing the objection to the use of homopolar machines based on their low voltage, since with sufiiciently high speed such machines may be designed for commercial purposes without an undue number of collector-rings, while the absence of a commutator makes them particularly suitable for high speeds.

One object of my invention is to provide a novel form of homopolar machine in which the second objection shall be met by the elimination of the armature reaction, which has hitherto rendered the regulation of such machines too poor for service where constant potential is required.

Another object of my invention is to provide simple means for compounding homopolar machines.

My invention will best be understood by reference to the accompanying drawings, in which 1 Figure 1 shows a side elevation in cross section of a machine constructed in accordance with my invention. Fig. 2 shows an end elevation of the field-magnet. Fig. 3 is an explanatory diagram, and Fig. 4 is a diagram of connections.

In the drawings, A represents the rotatable armature, mounted on the shaft S and carrying the armature-conductors (6, each of which v is connected at each end to a collector-ring C.

B B represent brushes bearing on the col.- lector-rings, by means of which the several armature-conductors may be connected in series.

F represents the field-frame, supporting the field-coil f and having bolted to it the fieldpoles F. As shown in Fig. 2, the faces of the field-poles F extend into close proximity with each other, so as to form a practicallycontinuous homopolarfield at the pole-faces. The magnetic flux may be considered as passing radially inward from the field-frame F across the air-gap a axially through the armature-body A and across the main gap to the field-poles F. The armature-conductors a are consequently rotating in a practicallycontinuous homopolar field.

Referring now to Fig. 3, the magnetic conditions are represented diagrammatically. The radial arrows 1 1 represent the main field flux passing outwardly from the armature A to the continuous field structure F. The armature-conductors a, cutting this field, will have set up in them electromotive forces which when the armature-circuit is closed will produce currents that are in the same direction in all the conductors. The current in each conductor produces a circular flux, as indicated by the circular arrows 2 2. These circular fluxes produce uneven distribution of the radial no-load field flux, since each circular flux assists the field flux on one side of the conductor and opposes it on the other. As the armature revolves this resultant uneven distribution tends to set up eddy-currents in the field structure. In order to oppose the tendency to eddy-currents, I provide the conductors (Z, which are short-circuited at each end by the rings D, as shown in Figs. 1 and 2. A squirrel-cage Winding is thus formed, which by the currents induced therein opposes all fluctuation of the flux at the inner periphery of field F, and thereby prevents loss of energy in eddy-currents in the pole-faces.

The uneven distribution at theinner periphery of field F is not the only result, however, of the circular fluxes set up by the armatureconductor. It will be noticed that the portions of all the circular fluxes cutting field F are in the same direction, and consequently they combine to produce a circular polarization of the field structure, as shown by the arrow 3. This circular polarization results in an increased flux density in the field structure, a reduction of the total fiux, and a consequent decrease of the terminal voltage of the machine. This circular polarization increases with the load on the machine and is the cause of the inherently poor regulation of homopolar machines as heretofore constructed. In order to oppose this tendency to circular polarization, I increase the reluctance of its path by interrupting its continuity. By means of the polar construction shown in Figs. 1 and 2 wedge-shaped radial air-gaps interrupt the circumferential continuity of the field structure. With this arrangement the magnetic reluctance ofiered to the circular polarization is enormously increased, While the practical uniformity of the homopolar field adjacent to the armature is maintained.

In order to further compensate for the tend ency to circular polarization, an opposing circular polarization may be produced, if desired. Thus I have shown the coils f supported on the lateral surfaces of the pole-pieces F, by means of which a circular polarization of the field structure may be produced. By this means not only may all tendency to circular polarization be prevented, but also a compounding of the machine may be produced. Thus if the coils f are connectedto produce a constant circular polarization when the armature is on open circuit, this circular polarization will be unopposed, and an increased density will be produced in the field-poles. Now as the armature is loaded the tendency to circular polarization by the current in the armature-conductors will oppose the polarization due to the coils f Thus the circular polarization will be reduced, the density will be reduced, the total flux will be increased, and the terminal voltage for the machine will be increased. In this manner the machine may be compounded or over compounded, as desired. For this compounding the coils f may be connected in shunt to the terminals of the It will be understood that my invention is not limited to the specific form of magnetic circuit shown in the drawings, but is applicable to the many different forms of magnetic circuit which have been heretofore proposed for use in homopolar machines. Accordingly I do not desire to limit myself to the particular construction and arrangement here shown, since changes which do not depart from the spirit of my invention will be obvious to those skilled in the art.

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

1. In a dynamo-electric machine, a drumarmature, a plurality of conductors carried at or near the periphery of said armature, a field structure having a plurality of like poles extending radially inward and surrounding the armature, said poles extending into close proximity to each other adjacent to the armature so as to form a homopolar field and diverging from each other as they recede from the armature.

2. In a dynamo-electric machine, a drumarmature, a plurality of conductors carried at or near the periphery of said armature, and a homopolar structure surrounding said armature arranged to produce a radial homopolar flux and having its circumferential continuity broken by radial wedge-shaped air-gaps.

3. In a dynamo-electric machine, a homopolar field structure provided with a winding arranged and connected to produce a practically constant circumferential magnetomotive force in said structure.

4. In a dynamo-electric machine, a homopolar field structure provided .With a winding arranged and connected to produce a circumferential magnetomotive force in said structure independent in strength of the amount of armature-current.

5. In a dynamo-electric machine, a homopolar field structure, a shunt-field winding, and an auxiliary shunt-winding arranged to produce a circumferential magnetomotive force in said structure.

6. In a dynamo-electric machine, a homopolar field structure, a winding arranged and connected to produce a substantially constant magnetomotive force radial with respect to the armature, and an auxiliary field-winding arranged and connected to produce a circumferential magnetomotive force opposed to the magnetomotive force of the armature.

7.. In a dynamo-electric machine, a ho mopolar field structure and short-circuited In Witness whereof Ihave hereunto set my conductors supported at or near the surface hand this 21st day of April, 1904.

of said structure opposite the armature. CHARLES P STEINMET7 8. In a dynamo-electric machine, a ho- 5 mopolar field structure and a squirrel- Witnesses:

cage winding supported at or near the sur- BENJAMIN B. HULL,

face of said structure opposite the armature. HELEN ORFORD.

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