US1547689A - Changing of pole connections of four-phase windings - Google Patents

Description

July 28, 192i 1,547,689

R. RUDENBERG CHANGING POLE CONNECTIONS 0F FOUR-PHASE WiNDiNGS Filed Dec. 15, 1920 2 Sheets-Sheet 1 Jul 28,1925." w 1,547,689

R. RUDENBERG cnaud'iue or row qonuacnons or FOUR-PHASE wxmamqs Filed Dec, 15, 1920 2 shuts-shed 2 Patented July 28, 1925.

UNITED STATES REINI-IOLD RT IDENBERG, OF BERLIN-GRUNEWALD, GERMANY, A'SSIGNOR T SIEMENS- SCHUCKERTWEBKE GESELLSCHAFT MIT BESCHRANKTER HAFTUNG, OF SIEMENS- STADT, NEAR BERLIN, GERMANY, A CORPORATION OF GERDIANY.

CHANGING OF POLE CONNECTIONS 0F FOUR-PHASE WINDINGS.

Application filed December 15, 1920.

rangement whereby the pole connections of four-phase windings can be changed.

Generally speaking, the windings ot' multi-phase motors having a variable pole number require a very large number of switches in order to connect the winding branches for each pole number in such a manner with each other that the passage of current through the windings will result in obtaining the required number of mag netic poles.

My present invention relates to an improved arrangement for changing the pole connections of four-phase windings. An embodiment of said arrangement is shown diagrammatically by way of example in Figs. 1 to 5 of the accompanying drawings, in which- Fig. 1 shows in conventional form a developed ring armature winding supplied with 2- or l-phase alternating current and adapted to produce a 2-pole or t-pole magnetic field;

Fig. 2 shows in conventional form a developed drum winding changeable from 4.

to 6 poles;

Figs. 8 3 4 4 5 and 5 show different modifications of the invention according to which the number of switches required for the pole-changing operation is considerably lessened, Fig. 3 showing a star connection; Fig. 3 a t-phase connection of eight coils serving for changing the number of poles; Fig. 4? a l-phase connection; Fig. 4 the manner of changing this l-phase connection into a double star connection; and Figs. 5 and 5 still another mode of changing the 4-phase connection into a double star connection requiring still fewer switches.

Fig. 1 shows diagrammatically a developed ring armature winding, adapted for feeding a two-phase, or even a fourphase current, and producing according to Serial No. 431,050.

the manner in which the indii'idual coils are connected, either a two-pole or a fourpole magnetic field. All the ends of the oils indicated must be so closely connected with each other for the purpose of obtaining two poles that the phase currents A and B will flow along the periphery of the armature in the succession marked by the upper line of reference letters. On the other hand, to produce four poles, the coil ends must be so interconnected that the coils are traversed by the phase currents a, i) in the succession indicated by the lower row of reference letters. Obviously the diverse indication of the phases by means of capital and small letters for the various pole numbers, has only been done for clearness. In practice the phases A, a on the one hand, as well as B, Z) on the other, may be derived from the same external phase lines.

For the pole changing arrangement according to Fig. 1, which produces a complete two-phase magnetic field for each of the two pole numbers, there are required eight separate coils which must be suitably changed when passing from one pole number to another, in such manner that, for instance, coil 1 for both pole numbers is traversed by phase current A and a, respectively, coil 2 for the two-pole field by phase A, for the four-pole field by phase 6; coil 3 for the two-pole field by phase B, for the four-pole field by phase a and so on. As a whole, the eight coils in the case of alternation, must be changed according to the following properly arranged diagram:

Aa Ab Aa Ab Ba Bb Ba Bb At the same time it should be remembered that it is immaterial whether in this connection the reference letters for the phases of both pole numbers are reversed or not, say whether the diagram read b?) or B6, since each of the coils possesses two free ends which, according to requirement, may be mutually interchanged.

These eight coils are provided with sixteen switch ends, in addition to which there are four connections coming from the network, so that in order to change the pole connections of the winding in all twenty contacts must be connected in various ways.

There are further required for each of the pole numbers ten two-pole switches, making in all twenty switches.

Since the aforementioned table comprises every imaginable method of interlinking the various phases, the number of eight coils from four to six poles, i. e., at the ratio of 2:3, by connecting thecoil ends either as indicated by the capital letters A, B, or else according to the small letters a, Z) to the external phases. In the first case there will be created a four-pole, in the second a six pole magnetic held, as clearly indicated by the arrows in the drawing.

The number of twenty switches required in accordance with these explanations for changing every pole connection of this kind, is undesirably big for ordinary service. It the winding for both pole numbers is to be employed in a star connection, then it is not possible to materially reduce the number oi said switches.

In accordance with my invention the number of switches required may be considerably reduced provided, when passing over from one pole number to another, the interlinking of the multiphase winding be simultaneously altered, by changing over to a four phase ring connection. In accordance with my present invention, this change is effected in such a manner that for both manners of connection, each two of such coils as carry in star-connection current of the same phase in series or paralleli. e., belong to the same branchremain unaltered. On thus passing from one number of poles to the other, according to the invention two coils are always disposed so that, when the points 01 connections for the outer connections are correctly chosen, they are correctly connected together for both pole phases. It is thus not necessary to place any separatin switches between them, all that is necessary being. a branch conductor at the point ofconnection;

Figs. 5 and 3' show in what way. such a change over may be efiected, Fig. 3 showing the star-connecti0n and Fig; 3 the four phase mesh connection of all eight coils. The passing from one to the other is in this case effected in such a manner that the net connections which are connected to the outer ends of the starbranches, consisting each of two coils or coil-groups in series, are connected to the connecting points which remain unaltereduwh'en the changeover takes place,

while the outer ends of the star branches form the figure of a square.

are connected together to form a four phase mesh, i. e., the sides of the star are closed to The location of the current supply for the time being is indicated by an arrow, and in both figures the coil ends are provided with an indication as to which phase currents pass in and out, respectively. By comparing the currents flowing in the homologous coils of Figs. 3 and 3 with the above table, it will be observed k that in this method or" changing the connection there are actually present all required combinations. In the case of the {our phase connection the internal phase currents are marked by reference letters, while the external currents which are composed or" the former, are indicated by Roman numerals. In Fig. 3 moreover is indicated by means of Arabic numerals the particular position which the difierent coils must possess at the periphery 01" the armature when changing a pole connection, having a ratio of 1:2, according to Fig. l. Bycounting the various connections between the coils and the supply lines, it will be found that altogether twelve tap lines must be led out of the motor, and that fourteen switches will be required to change the connection, in other words, a considerably smaller number than at first appeared necessary.

Still more favorable conditions will be obtained by proceeding not from a star connectior as in the case just consideredbut ratl er from a tour-phase connection, and

then changing over to a star connection with two parallel branch s, in which casealways two coils will again remain connected. A connection of this kind isillustrated in Figs. l and a". In this arrangement for the purpose of passing over from a foursphase to a star connection, the square is changed to a ouble star in so far as always two coils adjoining the corners of the windings of the square, are connected in 'allel to form the ray or branch of a star.

Pursuant to the sense of the winding, the phase currents present for the time being are again indicated in this figure by their reference letters In this case it is not necessary to open the point of connection of coils 2 and l, since it is located in the double star connection in the star center of the system, and hence no compensating currents are liable to arise between said point of connection and other phases. Besides in this case no exclusively two-pole one-contact switches are required, while a further saving will be obtained by employing suitably simplified switches at the points where in a star connection three winding points 7 have to be united with each other. Moreover, the two left hand external supply lines shown in Figs. 4& and 4 can always be left in their position on the winding. There are thus required, in the case of this change of connection, altogether five ordinary and four three-pole switches.

The method of changing the connection from tour-phase or square to double star, as last described, may be rendered still more simple, by eflecting the connection between the coils and the supply lines along the lines shown in Figs. 5 and 5 in order to pass over from one pole number in a tour-phase connection to another in a double star connection, all that need be done is to shift the four supply lines, which in the tour-phase connection according to Fig. 5 are led around the corners of the square, according to Fig. 5 in a suitable succession along the center of the sides, and to short-circuit the square in a diagonal line.

it will be understood without further e2:- planation from the above given indications for the phases that, on the one hand, the proper current flows to them as shown in the diagram Fig. 5 and that, on the other hand, all the changes oi phases for the coils are present, which according to the hereinefore given table, are required for every change of two-phase pole connections. The change-ofpole connection according to Figs. 5 and 5 which, like the others, is adoptable for any desired winding diagram, requires in all only eight tap lines, which must be carried to the outside from the motor, and only nine two-pole single throw switches. The 'number of switches is accordingly reduced to less than one half of that originally required, While at the same time the interlinking of the winding has been changed, as a result of which the effective number of series turns is altered at a ratio of 1:2.

An alteration of the number of series turns of this kind is desirable for many purposes. For by this alteration there is for eX- ample given the possibility of running the motor at a reduced speed with a greater et' tective number of series turns, than at high speed. On principle, the manner of applying the two-pole numbers to the two kinds of switches described may be chosen at will. The arrangement of a winding having a large effective number of series turns, i. e., of the star connection according to Figs. 3* and 8 and of the four-phase connection according to Figs. 4 to 5 in connection with a higher pole number will, however, be

two-pole found expedient for the reason that the voltage of the system being the same, there will be obtained approximately the same flux in the air gap in the mot-or.

I claim:

1. The method of changing the pole connection in tour phase windings, which consists in simultaneously altering the inter linking of the multiphase winding when passing over from one pole number to another, by changing over from star to tour phase ring-connection in such manner that for both pole connections a connection is maintained between the individual coils of those pairs of coils which when linked in star connection, carry current of the same phase.

2. The method of changing the pole connection in tour phase windings, which con sists in simultaneously altering the interlink ing of the multiphase winding when pass ing over from one pole number to another, by changing over from star to four phase ring-connection in such manner that for both pole connections a connection is maintained between the individual coils of those pairs of coils which when linked in star connection, carry current of the same phase, the network connections in case of tour phase arrangement being applied to the points of said maintained coil connections.

3. The method of changing the pole connection in four phase windings, which consists in simultaneously altering the interlinking of the multiphase winding when passing over from one pole number to another, by changing over from star to four phase riiig-connection in such manner that for both pole connections a connection is maintained between the individual coils of those pairs of coils which, when linked in star connection, carry current of the same phase, the change-over from four phase ring-connection to star-connection being effected by maintaining the connections of all the coils, shifting the network connecting points from the corners of the theoretical square formed by the coils to the center of the sides thereof, and by short circuiting said square by at least one diagonal connection.

In testimony whereof I afiix my signature.

REIN HOLD RUDENBERG.

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