US730214A - Transformer. - Google Patents

Description

No. 730,214. PATENTED JUNE 2, 1903.

Y M. LEBLANC.

TRANSFORMER. APPLIGATION FILED JAN. 4. 1901.

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PATBNTBD JUNE 2, 1903.

M. LEBLANG.

TRANSFORMER.

APPLIIOATIOH mum JAN. 4. 1901-.

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PATBNTED JUNE 2, 1903.

M. LEBLANG.

TRANSFORMER. APPLICATION FILED JAN. 4. 1901.

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No. 730,214.' PATBNTED JUNE 2, 19 03.

v M. LEBLANG.

TRANSFORMER.

APPLICATION FILED JAN. 4. 1901.

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UNITED STATES Patented June 2, 1903.

PATENT OFFICE.

MAURICE LEBLANO, OF PARIS, FRANCE.

TRANSFORMER.

dated June 2, 1903.

Application filed January 4, 1901. Serial No. 421038; (No model.)

To all whom it may concern:

Be it known that I, MAURICE LEBLANo, a citizen of the Republic of France, and a resident of Paris, France, have invented certain new and useful Improvements in Transformers, more particularly of the rectifying type, of which the following is a specification.

Let us consider an iron core, preferably of the ring type, about which circuits are wound. Let us, furthermore, consider that we passinto these circuits currents of any kind-such, for instance, as monophase or polyphase currents-01, if you please, let us pass therein continuous currents in such a manner that the leads through which the continuous currents are fed to the circuits about the ring move around the circumference of the ring. In each of these cases there will be developed in the iron of the ring a rotating magnetic flux, which, generally speaking, will be compound in character.

To understand what I mean by the compound character of the flux, let us considerv the flux in the ring at a given instant of time, I

just as if this condition were permanent. Let us, furthermore, consider a section made through the ring by a radial plane perpendicular to the plane of the ring, which radial plane makes an angle to with the Vertical diameter of the ring. Let us designate by Q the intensity of the magnetic fiux which traverses the section of the ring above referred to. WVe may consider the flux Q as a function of the angle to and may write @zf(w;) but the function 4 attains the same value each time the angle to is increased by 2 11. We can therefore represent the functionf (w) by a development according to the Fourier theorem by designating by 90 1;), (p constants representing fluxes and by p, [3 /5 constants representing diiferences of phase, as follows:

derstood that I have been considering the flux in the ring at a given instant of time. I

have assumed that the magnetic flux which exists in the ring at a given instant of time has become, as it were, frozen in the ring, so that we may look at it and examine it. I have not in that which precedes been considering such variations in the flux as are brought about in successive intervals of time, but have merely been considering the variations of magnetic flux in thecore or ring as you pass from point to point of the ringin a given inst-ant of time. To understand, then, what kind of a flux is represented by the first term of the above development-namely, by the term :1), sin. (to fl )We must start with the angle to from an initial value /3 and let it increase, going counter clockwise through to three hundred and sixty degrees of are. When the angle to is equal to fl the sine of the angle to A is zero, which means that at the point of the ring represented by [J there are no lines of force traversing a radial crosssection of the ring. As the angle to increases beyond [3,, sin. (w/ increases according to the sine law until w reaches ninety degrees +/J At this point the sine of the angle is a maximum. We therefore find that the number of lines of force constituting the flux represented by 90, sin. (10- [3,) is zero at one crosssection of the ring and that this number increases gradually in amount and reaches a maximum at a cross-section displaced from the zero cross-section by ninety degrees. Still moving counter-clockwise around the ring the number of lines of force in a given crosssection gradually diminish until we reach the cross-section one hundred and eighty degrees removed from the zero cross-section, in which the number of lines of force is again zero. Moving on around the ring in a counter-clockwise direction, the number of lines of force in any radial cross-section of the ring again increase; but this time the lines of force run in the opposite direction. Their arithmetical number reaches a maximum in that cross-section of the ring which is two hundred and seventy degrees removed from the originalzero cross-section, after which, their direction still remaining the same, they diminish in number until we have zero-lines of force when the,

starting-point is reached-that is, considering the ring divided into four quadrants, the lines of force in the first and second quadrant run in one direction in the ring, and in the third and fourth quadrant they run in the opposite direction in the ring. Considering the number of lines of force in any radial cross-section of the ring, they are zero at two diametrically opposite points and are at maximum at two other diametrically opposite points displaced from the first points by ninety degrees. Between the zero and maximum points the number of lines of force in any radial cross-section increases gradually in accordance with the sine law.

The flux which I have just described and which is represented by g0, sin. (av-[ 1) I define as a simple or pure sinusoidal flux of two branches, the flux which is represented by (7),. sin. (7LLUfln) as a flux of 2n branches.

Now the object of my invention is to take any compound magnetic flux and to obliterate therefrom any given element or elements of the flux which I select. Thus it is particularly useful in a variety of electrical apparatuses to have therein a pure sine flux of two branches and such flux only. In fact, a uniformly-rotating sine flux of two branches, as above defined, represents the pure or ideal form of a rotating field of constant intensity. In accordance with my invention I am enabled to screen out or obliterate all of the sine fluxes of a greater number of branches than two, given in the above expression, and to leave merely that element of the flux which I have called a two-branch flux and which produces the uniformly-rotating constant magnetic field. I leave, in other words, the flux, which is represented by the first element of the development above given, which produces the constant-rotating field, and screen or obliterate the fluxes corresponding to each and all of the other elements of the development above given, being the terms of the higher orders in the series and which would tend to disturb the constancy of the field. Put in different words, I take the compound flux which exists in the apparatus and 1 screen out all of the disturbing elements of that flux and leave only the pure sine flux oftwo branches, which produces a strictly-constant and uniformly-rotating magnetic field. These objects I effect by a system of compensating windings, which will hereinafter be fully described.

Manifestly the general principle of the invention as I have thus explained it has a variety of applications. Thus, for instance, I can apply it to a polyphase transformer, in which polyphase currents of a given order are transformed into polyphase currents of the same orot'any other given order. In accordance with my invention I would in such transformer obliterate any magnetic flux or electromotive force generated therein which is not of the desired phase. Thus, for instance, if I should transform a biphase current intoa polyphase current ofa larger number of phases the successive electromotive forces of the secondary polyphase system brush and its holder.

may not, in the absence of my invention, be symmetrical or equidistant in phase, and thereby the secondary system will not he balanced; but by the use of my compensating windings the system is forced to be balanced; but what is probably the most important application of my invention is found in its application to rectifying-transformers-that is to say, transformers in which a monophase or polyphase current is transformed into a continuous current-by connecting the secondary windings to the segments of acomrnutator or in which, vice versa, a continuous current can be transformed into a monophase or polyphase current by feeding the continuous current through the commutator to what were before the secondary circuits and by tapping monophase or polyphase currents from what were before the primary circuits.

In rectifying-transformers as heretofore constructed the secondary coils are usually entirely embedded in iron and the electromotive forces of self-induction of commutation are enormous. In fact, the electromotive forces ofself-induction,practically speaking, make commutation impossible. By' the use of my compensating windings, however, regardless of the sudden change of current during commutation by the short-circuiting of the coils, the electromotive forces induced in the successive coils correspond to a symmetrical polyphase system. It is thus possible to commutate a closed magnetic-circuit transformer without meeting any excessive electromotive force of self-induction. I have therefore chosen such rectifyi ng-transformers in order to illustrate the principle of my invention.

In the drawings, Figure I shows a vertical cross-section of a rectifying-transformer as it is made in accordance with my invention. Fig. 2 shows a front elevation thereof. Fig. 3 shows a rear elevation of the same. Fig. 4c shows a section of the ring-core. -Fig. 5 shows a diagram of the windings. Fig. (5 shows a detail of a mode of connecting the secondary circuits. Figs. '7, 8, and 9 show details of the centrifugal sliding com mutator- Figs. 10, 11, and 13 show details of a modified form of the centrifugal sliding commutator-brush and its holder. Fig. 12 shows a diagram of the system.

The rectifyirig-transformer is composed of a transformer-ring 1, which is generally fixed and which is shown separately in Fig. 4. Added to this is an annular commutator 2, (shown to the left of Fig. 1 and which in this case is stationary.) \Vithin this commutator is rotated a spider 4, carrying brushes 3, whose outer faces make and maintain contact with the inside surface of the commutator-segments in a manner which I will more fully describe later on. A small synchronous two-phase alternating-current motor (shown to the right of Fig. 1) serves to rotate the brushes.

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is secured to a shaft 25, which has its bearings in the frame of the transformer and has 7 hand, the number of terminals of the alterrao,214

The armature 5 of the synchronous motor 1 keyed to it the spider 4, towhich the brushcarriers are secured. The field-magnets 6 of the small motor are mounted on a common yoke 61, which is rotatably mounted within the annular bearing 62, which is shown as in one piece with the supporting-frame of the transformer. From the yoke 61 extends a toothed sector 7, which meshes with a pinion or sector 8, secured to a shaft 9, extending to the commutator side of the machine, where it may be formed with a squared end to receive a crank by which the shaft may be turned. In this manner the field-magnets of the small biphase motor are made adjustable circularly. To any shift given to the field corresponds a lead or lag in the set of the brushes on the commutator 2 of the transformer. The same result is thus obtained as is ordinarily obtained in the case of a rotary commutator by shifting the stationary brushes with respect thereto.

Considering more in detail the spider 4, which carries the brushes 3, it is seen that the number of arms in this spider are made even. In the case shown their number is eight. The odd-numbered arms are electrically connected with each other and with a ring 10 in Fig. 2, and the even -numbered arms are electrically connected with each other and with the ring 11 in Fig. 2. Upon the rings 10 and 11, which have just been described as electrically connected with the odd and even numbered arms of the spider, bear fixed brushes 12 13, and these brushes in turn are connected to binding-posts marked plus and minus respectively, in Fig. 2. These two binding-posts are the terminals of the continuous-current circuit of the rectifying-transformer. On the other nating-current circuit which enters or proceeds from the rectifying-transformer varies according to whether the apparatus is to transform or yield monophase, biphase, or multiphase currents; but in all cases the alternating-circuit terminals will be displaced around the circumference in a symmetrical manner. In the case represented in Fig. 2 there are four alternating- circuit terminals 14, 15, 16, and 17, which means that the apparatus is to utilize or yield biphase currents.

The apparatus thus far described is seen to consist in the main of a transformer-frame having terminals for the alternating current, a fixed hollow annular commutator, on the inside of which sets of brushes revolve which take off the continuous current, and of a small biphase motor which serves to drive these brushes. The field of the'biphase motor is shiftable to produce the effect of a shift of the brushes bearing on the commutator for lead or lag. The field of the biphase synchronous motor is supplied with direct ourrents. The armature of the biphase motor receives its alternating driving current through the brush es 22 23 24, which are shown in Fig. 3 and which bear on the rings marked with the same numbers. (Shown tothe right in Fig. 1.) The brushes 22 23 24 are in turn connected to a source of biphase current in a manner which will be described later 011. The number of pairs of poles of the biphase motor is equal to the number of groups of commutator-segments, to be hereinafter described. This number may be greater than the number of poles of the transformer,which in the present case is taken as two. To the field-pole 6 of the biphase motor I secure a magnetic shield 63, which may be of the squirrel-cage type shown, the construction of which is more fully illustrated in the prior patent to Hutin and Leblanc, No. 529,272, of November 13, 1894. The functions of the magnetic shield 63 will appear farther on.

A crank 25 (indicated in Fig. 12 in dotted lines) may be used for starting the synchronous motor by hand.

I come now to describe the ring-core of the transformer and the windings which it carries. To this end particular attention is called to Figs. 4and 5. The body of the transformerring 4 is composed of a series of superposed segmental iron laminze 27. In the case shown these segments are quadrants, and together they constitute a closed ring. Inside this ring there is a toothed ring 26, which is also built up of superposed iron laminze. In the case shown the laminae 26 are full circles and are provided with teeth extending radially outward. Upon the segments of the outer iron ring 27 the bobbins of the transformer are strung, whereupon the segments may be secured together to form the magneticallyclosed core. Thereupon the toothed ring 26 is slipped inside the ring 27 in such a manner that the bobbins upon the ring 27 lie in the slots between the teeth of the ring 26. The lines of force which constitute the magnetic fluxes which may be generated in the iron structure 26 27 may be represented by the broken lines in Fig. 4. It will be seen that these lines of force lie almost wholly within the iron and that the air-gaps which they have to traverse are of small width.

Each bobbin which is strung on the transformer core is composed of four separate coils. The inner coils P in Fig. 4 I will treat as the primary coils of the transformer. The coils S of Fig. 4 will be treated as the secondary coils of the transformer. The two sets of coils n and 'n are what will be hereinafter called the sine and cosine com-. pensating coils, respectively, of the transformer.

Examining Fig. 5, the manner of interconnecting the primary coils to form the primary windings of the system and of interconnecting the secondary coils to form the secondary windings of the system will be clear. The

manner of connecting the compensating sine and cosine coils will be described later on.

Each secondary coil 8,, S S to S has the same number of turns. Each primary coil P P P to P has the same number of turns. The number of turns on the primary coils may, however, differ from the number of turns on the secondary coils, the ratio of these number of turns on the primary and secondary coils giving the ratio of transformation, as is well understood. There are shown in Fig. 5 four groups of twenty commutator-segments each. The twenty segments in each group are numbered consecutively 1, 2, 3 to 20. The four segments 1 are electrically interconnected, as shown, by the wires on the outside of the commutator in Fig. 5. So the four segments 2 of the four commutator groups are electrically interconnected. In general, like numbered segments of the four commuiator groups are electrically interconnected.

The secondary coils S S to S are connected in series, as shown in Fig. 5. One end of the secondary coil S is tapped to one of the four commutator-segments 1 and is thereby electrically connected to each of the four commutator-segments l. The corresponding end of the secondary coil 8,, which is the other end of'the secondary coil 8,, is electrically tapped to one of the four commutator-segments 2 and is thereby electrically connected to each-of the four commutator-segments 2, and so on.

The primary coils P P to P are also connected' in series. The terminals of the alternating-current leads are connected to the primary winding thus formed at points equally displaced around the circumference. In the case shown the terminals 14, 15, 16, and 17 of a biphase circuit are connected at the points shown in Fig. 5, which are ninety degrees removed from each other. If a monophase current is to be fed to the primary coils, the two terminals of the monophase circuit may be connected to the points 15 and 17, which are removed from each other by one hundred and eighty degrees.

In all that precedes I have assumed a G'ramme winding; but manifestly any other suitable type of winding may be employed.

So far as above described it will be seen that I feed a monophase or polyphase current to'the primary winding P, and thereby generate alternating currents in the secondary windings S, which are tapped to the commutator-segments, from which I may take a continuous current by means of the rotary brushes, which bear against the commutatorseg'ments, as already described. Should I desire, however, to transform alternating current of anynumber of phases into alternating currents of the same or a different number of phases, it is evident that I can dispense with the commutator and brushes and that I can feed alternating monophase or polyphase currents to the primary windings and take alternating currents from the secondary winding by simply tapping these secondary windings at pointssym metrically displaced around the circumference of the ring. Thus,forinstance, my invention is peculiarly adapted for transforming polyphase currents of any number of phases into polyphase currents of a very large number of phases, and this can be done by tapping the secondary circuit directly, thus dispensing with a commutator. It will also be evident without further description that the primary and secondary circuits are interchangeable and that the transformer is reversible. Nor does it seem necessary to mention that I can use a revolving commutator and stationary brushes instead of the stationary commutator and the revolving brushes which I have shown. So, too, I may substitute for the type of motor which I have shown any other suitable type of motor.

I now come to a detailed description of the two sets of compensating coils n 'n and their interconnection, which are diagrammatically indicated inside the circle formed by the primary coils P of Fig. 5. The arrangement of these coils and their operation constitute the principal feature of the present invention.

The two compensating circuits, each of which is cmpotmd.We have now to consider the two compensating circuits, each of which is compound. The coils composing these windings as I have shown them bear a certain resemblance to the coils of a Gram niering winding; but this is not essential.

We assume that the number of slots in the iron ring is represented by 2 K, where K is an even integer, which is made as large as the requirement of construction permits. IVe number these slots in order from 1 to 2 K in the same direction around the ring, assuming for convenience that this direction is counterclockwise. The slots numbered from 1 to lie in the first quadrant, those from 1 to K lie in the second quadrant, those from K 1 to 3 K lie in the third quadrant, and those from 1 t0 2 K lie in the fourth quadrant.

I have already stated that in each slot as there is a primary coil Paand a secondary coil S00. These are the ordinary primary and secondary-coils of the transformer. In addition to these two coils, however, I place in each slot w two other coils, one of which is to be included in the sine compound compensating circuit and the other of which is to be included in the cosine compound compensating circuit. Designating by n the number of convolutions or turns of the coil in the slot m which is to be included in the sine compensating circuit and by 'n the number of convolutions or turns of the coil in slotsc which is to be included in the cosine compensating circuit I determine these quantities n and n representing the number of turns in the compensating coils, by the following formulae:

where tis some arbitrary constant. I may for convenience speak of the coils n as the sine coils and of the coils n, as the cosine coils.

The manner of interconnecting the sine coils and the cosine coils is diagrammatically indicated in Fig. 5. The sine coils are indicated by full lines. The cosine coils are indicated by broken lines. The sine coil and cosine coil in the same slot are indicated by a full line and a broken line, respectively, lying adjacent and parallel to each other. The first quadrant is taken as running from the upper end of the radius, extending vertically upward and proceeding counter-clockwise to the horizontal radius extending to the left. It is seen that each sine coil in the first quadrant is connected to the sine coil in the second quadrant, which is removed therefrom by ninety degrees. 50 each sine coil in the fourth quadrant is connected to the sine coil in the third quadrant, which is removed therefrom by ninety degrees. Similar remarks apply to the cosine coils. Thus, for instance, one end of each sine coil of order 00 in the first quadrant is connected to the corresponding end of the sine coil in the second quadrant, which is removed therefrom by ninety degrees-that is to say, the outer end, for instance, of a sine coil 00 in the first quadrant is connected to the outer end of the sine coil m+-in the second quadrant, being in this case the sine coil of order a: 5, since 2 K is equal to twenty. So, too, one end of each sine coil in the fourth quadrant is connected to the corresponding end of the sine coil in the third quadrant, which is removed therefrom by ninety degrees that is, the outer end, say, of a sine coil of order m in the fourth quadrant is connected to the outer wire of the sine coil of order a; in the third quadrant. The free ends t branch having their order displaced by or by ninety degrees and the two sets of ends of these K parallel branches being connected to the rings I and II, respectively. Similar remarks apply to the cosine coils and to the second compensating circuit which includes them. One end of each cosine coil of order m in the first quadrant is connected to the corresponding end of the cosine coil in the second quadrant, which is removed therefrom by ninety degrees. So, too, one end of each cosine coil in the fourth quadrant is connected to the corresponding end of the cosine coils in the third quadrant, which is removed therefrom by ninety degrees. The free ends of the cosine coils in the first and fourth quadrants are connected to the ring III of Fig. 5, and thefree ends of the cosine coils in the second and third quadrants are connected to the ring IV of Fig. 5. It is therefore seen that the cosine compensating circuit, in which are included all the cosine coils, is composed of a network of K parallel branches, each branch containing two cosine coils in series, the two coils in any given branch having their order displaced by or by ninety degrees and the two sets of ends of these K parallel branches being connected to the rings Ill and IV, respectively. The rings I II III IV are connected to the terminals 18 19 2O 21. (Shownin Figs. 2 and 3.) Let us once for all mark the circumferential points on the soft-iron ring by the angles which radii drawn through these points make with the vertical radius of the rin Thus the vertical or top point on the ring, as seen in Fig. 5, for instance, will be marked 0, the point on the horizontal diameter to the left will be marked the point on the vertical radius extending downward will be marked 180, and the point on the horizontal diameter to the right will be marked 270. Let us now consider that the magnetic flux iu the soft-iron ring at any given. instant of time is of such a character that the intensity of the flux at any radial cross-section of the ring or, what is the same thing, the number of lines of force which traverse any cross-section of the ring made by a radial plane perpendicular to the plane of the ring may be represented as the sine of the angle which the radial plane under consideration' makes with any given or fixed radius of the ring which is selected as the base or starting-point at the given 'instant of time. To fix ideas, we assume that this base at the given instant of time under consideration is marked by three hundred and forty degrees, or, what is the same thing, by'minus twenty degrees. The flux which we at the given instant of time suppose to exist in the iron ring will therefore be zero at the point marked by minus twenty degrees on the ring. It will grow more and more dense as we pass through the angle zero on the ring and will reach its maximum at the point of the ring corresponding to the angle seventy degrees. It will then decrease in intensity and become zero at one hundred and sixty degrees on the ring.

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Passing along the ring in the same direction, the flux will now flow in the opposite direction, butincreasein arithmetical magnitude nntilit reaches its negative maxim um at two hundred and fifty degrees on the ring, whence its arithmetical magnitude will again diminish until at the angle of three hundred and forty degrees or minus twenty degrees the flux is again zero, and the rate of increase and decrease of the fiurf as you pass around the ring will follow the simple sine law. We now assume that this simple sine flux, which at the given instant of time under consideration is of zero value at minus twenty degrees on the ring, is rotated at a uniform velocity through an infinitely small angle. The value of the flux at each given point on the ring is, as I have before stated, proportional to the sine of the angle or are which runs from the point under consideration to the point chosen as the base, which in this case is minus twenty degrees and which in the general case we can take as minus a degrees of arc. The electromotive force which will be generated by-the rotation of this flux at this given instant of time in the sine coil found at the point of the ring under consideration will be proportional to the product of the number of turns of'wire in the sine coil under consideration and to the variation of the number of lines of force which pass through the ring. As the number of lines of force at any point of the ring is measured by the sine of the are which separates thatpoint from minus twenty degrees or minus adegrees, the variation of this number of lines of force will be proportional to the cosine of the angle which separates the point under consideration from the base-line, for it is known to any student of the calculus that the differential coefficient of the sine of an angle with reference to the angle is equal to the cosine of the angle.

Without here giving the calculation it can be shown that the electromotive force which is generatedinanyoneofthe K parallelbranches of the compensating sine circuit is independent of the quantity as. This means that at any given instant of time the electromotive forces generated in each one 'of the K parallel branches of the compensating sine circuit by the rotation of the sim ple sine flux are equal in magnitude and phase. The magnitude of the electromotive force generated at any given instant of time in each and all of the K parallel branches of the compensating sine circuit is, in fact, proportional "to the sine of the angle which the zero-point of the sine flux at the given inst-ant of time makes with the point on the ring, which we have designated as zero and from which the number of turns of wire in our sine coils are determined. It is thus seen that the rotation of this sine flux produces at one given instant of time zero electromotive force in all of the K parallel branches of the compensating sine circuit. At any other instant of time there will exist an equal electromotive force in same direction in all, which electromotive force is measured by the sine of a uniformlyincreasing angle-namely, the angle which represents the velocity of rotation of the sine iiux. We can prove the same thing for the cosine coils comprised in the compensating cosine circuit. WVe find that the electromotive forces in each of the K parallel branches of the compensating cosine circuits generated by the rotation of the pure sine flux are equal and in the same direction at any given instant of time and that themagnitude of the electromotive forces in any or all of the K branches of the compensating cosine circuit will be represented by the cosine of the angle which measures the rotation of the sine flux from any given starting-point, the starting-point being the same as that chosen when considering the compensating sine circuit. Let us now assume that the rings I and II of Fig. 5 are not connected to each other and that the rings 3. and 4 of Fig. 5 are not connected to each other. It is plain from what has been said that the rotation of a simple currents of any kind either in the compensating sine circuit or in the compensating cosine circuit. There will simply be generated a series of equal and equally-directed electromotive forces in the parallel branches of the compensating sine circuit, which means that no current will flow from any one of these branches to any other of these branches. A similar remark applies to the compensating cosine circuit. Should we, however, connect the rings I and II to two terminals of my biphase motor before described and the rings III and IV to the other two terminals of this biphase motor, it will be seen that sine and coquarter-phase currents will be supplied to the motor; but as each one of the K branches of-the compensating sine circuits has an equal electromotive force at each instant there will still be no flow of current from any one of the K compensating sine branches to any of the other K compensating sine branches and the balance or equilibrium of the system will not be disturbed. A similar remark applies to the cosine coils. Such connection of the rings I and II and of the rings III and IV to the terminals of the biphase motor will merely mean that the energy of driving such motor would be taken from the compensating coils without in any way interfering With the action of these coils so far as the rest of the system is concerned. I may, therefore, drive a biphase motor, when I need such a motor in my system, by connecting the terminals I, II, III, and IV to the terminals of the motor, or I may drive a biphase motor from any other independent source of current.

It is well understood in matters of this kind that when we speak of giving a coil a certain number of turns corresponding to the sine of an angle that we give zero turns to the coil 'each of these parallel branches and in the sine flux in the iron core will generate no.

sine currents or, what is the same thing, two

when the angle is zero and that we wind the coils in opposite directions when the sine becomes negative. It is unnecessary for me to enter into any minute detail as to the direction of windings of the various sine coils and of the connection of these sine coils in pairs, as this will all be evident to any electrician who understands the above and who sees that the result aimed at is an electromotive force in each of the K branches of the compensating sine circuit which shall be equal in magnitude and phase at any given instant of time. The corresponding remark applies to the cosine coils.

Assuming now that there is no external connection between the terminals I and II and between the terminals III and 1V, it will be manifest that the uniform rotation of what I have termed a simple sine flux in the iron ring, whether this rotation be clockwise or counter-clockwise, will cause no currents of any kind either in the compensating sine branches or in the compensating cosine branches. Electromotive forces will be generated in the various parallel branches of these compensating circuits; but these will all be equal in magnitude and phase, so that no current will flow from one branch to another. Therefore it follows that the uniform rotation of a simple sine flux or a pure sine flux in the iron ring will have no effect on the compensating circuits and the compensating circuits will have no effect on the uniformlyrotating sine flux. Each will exist precisely asiftheother werenotpresent. Thecompensating circuits will in no way tend to deform or distort the uniformly-rotating sine flux. On the other hand, it can be shown that any other type of flux than the uniformly-rotating simple sine flux-such, for instance, as a flux of 212. branches, as before defined-will cause the generation of electromotive forces in the compensating branches, which will not be equally directed, but will be such that to any 'electromotive force in one branch of a compensating branches short-circuit each other.

Putting this in another way,it means that the compensating circuits will act as magnetic screens for all types of fluxes in the iron ring except the simple sine flux and will squeeze out and destroy these fluxes, but the simple sine flux will be allowed to move in the ringjus't as if the compensating circuits were not present.

From what has been said above it will be clear that I take a rotating fiux of any char- -ating under acter-that is, a compound flux or one composed of a number of separate dephased components or of a number of components of different periods-and that I shape this flux by cutting therefrom one or more preselected components. More specifically stated, I take acoinpound rotating flux composed of a number of components of different periods, and I shape the flux by obliterating all but the pure sine flux of two branches which correspond to a uniformly-rotating constant magnetic field, It follows therefrom that the intensity of this two-branched sinusoidal rotating flux will depend only on the effective voltage developed between the terminals of the primary circuit or in case of a rectifyingtransformer on the voltage of the continuous current measured between the brushes. The intensity of this two-branch flux will be independent of the intensity of the currents which traverse the primary and secondary circuits. The result may be compared to that which would exist in the ordinary type of transformer for transforming monophase alternating currentsinto monophase alternating currents when such transformer is operideal conditions. Generally speaking, the ratio of the electromotive force in the secondary to the electromotive force in the primary circuit in suchtransformer is determined by the ratio of the number of turns of these two circuits; but this is only true under ideal conditions. WVhen theload comes on and the currents inthe transformer.

increase, the amount of magnetic leakage in the transformer varies, the normal flux is distorted, and the ratio of transformation no longer remains the same, and is no longer solely determined by the number of turns in the primary and secondary circuits, but va ries with the load.

7 My transformer when thetwo-branch sinusoidal rotating flux is produced therein may be said to act as a perfect transformer in which the variation of current strength, so long as there is no variation of impressed vol tage, produces no change in the flux, and consequently no change in the ratio of transformation. A constant potential at the terminals of the primary will therefore give a constant potential at the terminals of the secondary independent of the load. As before pointed out, such a rotating two-branched flux is peculiarly useful in a rectifying-transformer, since the coils, which are short-circuited by commutation, are not allowed to produce fluxes which interfere with the twobranched sinusoidal flux and are therefore not allowed to interfere with the transformation.

The transformation of monophase cm"- rents.The system of compensating circuitswhich I have above described will permit the formation in the transformer-ring of a sinusoidal two-branched flux rotating with uniform velocity; but these compensating windings have not the power of selecting between two sinusoidal two-branched fluxes one of which is rotating in one direction and the other of which is rotating in the opposite direction. Now if I feed a polyphase current to my transformer it will produce a flux rotating in one definite direction, which flux will generally of course be complex; but if Ifeed to the two diametrically opposite points of the primary winding of my transformer a monophase alternating current this monophase current will produce in the transformerring an oscillating flux which may be considered as the resultant of. two sinusoidal fluxes, one moving to the right and the other moving to the left inthe ring or, what is the same thing, one moving clockwise and the 7 other moving counter-clockwise in the ring.

The flux which moves clockwise inthe ring may be considered as the sum of a number of component fluxes of different branches, as above defined. The compensating circuit, as above described, will obliterate all the com" ponents but the simple sine'or two-branched component. So the flux which moves counter-clockwise in the ring will be composed of a number of component fluxes. The compensating windings, as above described, will obliterate all but the pure sine or twobranched component. It follows that if I feed a monophase current to the primary winding of my transformer supplied with compensating circuits its ring will be the seat of two sine two-branched fluxes, one rotating clockwise and the other rotating counter-clockwise. In this connection I call attention to United States Patent No. 630,233, August 1, 1899, to Hutin and Leblanc, page 3, line 23, the. Now it is necessary to obliterate one of these two rotating fluxes and to leave in the ring a single rotating flux of a simplesine two-branched character rotating in a given direction. In other words, itis necessary to obliterate one of the two rotating two-branched fluxes. This I do by connectin the com ensatin circuits of the transand I connect the two terminals of the united ,13, and 14, as shown in Fig.12.

case of other biphase circuits, so here I may use a common return. I therefore connect the terminals 18, 19, 20, and 21 of the sine and cosine compensating circuits to the rings 12, 13, and 14, which are the terminals of the biphase armature-oircuits of the synchronous motor, as shown in Fig. 12. It follows from this that whatevericurrents I have in the sine compensating circuit I have in one of the armature-circuits of the motor, and whatever currents I have in the cosine compensating circuit I have in the other armaturecircuit of the motor; butif I am feeding monophase circuits to my transformer the compensating circuits will be the seat of electromotive forces corresponding to two oppositely-rotating magnetic fields. Therefore the armature-circuits of the motor will be the seat of electromotive forces corresponding to two oppositely-rotating magnetic fields. One of these fields will move in a direction opposite to that of the rotation of the armature with a velocity of the armature, and will therefore be stationary in space. It will not be affected by the magnetic screen ingthe motor. The other rotating field will move with reference to the armature and in the same direction as the armature with a velocity equal to that of the armature. It willtherefore move in space or with reference to the magnetic shield ata velocity equal to twice that of the armature. The magnetic shield will therefore consume and thus obliteratethis rotating field. There will thus be left in the armature-circuits of the motor simply the currents corresponding to a single rotating field. It follows that the compensating circuits will also be the seat of currents corresponding toa single rotating field moving in a given direction and that the field rotating in the opposite direction will have been obliterated.

The mechanical:conneotion ofthe transformer-wimlings.--The compensating circuits are interconnected in a manner which from the electricalgstandpoint is clear from what has above been said. Mechanically speaking, the various points of these compensating circuits are connected to the points ninety degrees removed therefrom by the radial bars 28 of Fig. 1; or is there any peculiarity about interconnecting the groups of commutator-sectionsthat is, of connecting to each other the commutator segments marked 1 in Fig. ,5, of connecting to each other the commutator-segments marked 2 in Fig. 5, and so on. These interconnections are effected by means of the ordinary connecting-bars 29.

There remains to describe the connections of the secondary circuits to the commutatorsegments. It is generally necessary in practice that these connections should traverse the iron parts of the machine-frames. If the currents transmitted alongthese connections become intense, they may develop fluxes of importance in the metal castings which surround them, and these fluxes may exert an objectionable influence on the commutation or may bring about a development of unnecessary heat. in a manner represented in Fig. 6.

Each secondary spool of the transformer is built up of two spools having the same number of turns, but in which the wire is of half the cross-section-that is to say, instead of having a single secondary coil in a given slot I have two coils in the slot, one wound clockwise and the other wound counter-clockwise. In Fig. 6 the spools which are wound clockwise are represented by an undulating continuous line and the spools which are wound counter-clockwise are represented by an undulating dotted line. The portion of the machine-frame through which the connections from the secondary coils to the commutatorsegments run is indicated by the annulus 70. The points marked 1, 2, 3 to 12 on the outside of this annulus are supposed to represent the commutator-segments in the case that there is but one group'of these commutator-segments. Should there be a number of groups of these'commutator-segments,then the points 1, 2, 3 to 12 on the outside of the machineframe of Fig. 6 would run to the commutator-segments of a given group, it being understood that the commutator-bars of one group are interconnected to the commutatorbars of the other groups by the connections 29.

To fix ideas, let us consider the-secondary coil represented by the full undulating line 1 2 in Fig. 6 and the secondary coil which is associated with it in the same slot and which is indicated by the broken undulating line 7 8 of Fig. 6. The currents of these two coils will be in opposite direction. This means that the currents which traverse the two connections going through the aperture in the machine frame 70, which come from the points 7 and 1, respectively, will be traversed by equal current in opposite directions. The same remarks apply to any other pair .of associated connections which pass through an aperture in the machine-frame 70. In each case such pair of associated connections will respectively be traversed by currents in the opposite direction, so that these currents cannot give rise to any fluxes in the iron frame of the machine which they traverse.

The rotating centrifugal brushes-Although it is not necessary in the use of my compensating circuits, I have described the transformer as provided with a hollow commutator, inside of which the brushes rotate. In order to have the brushes bear against the commutator-segments with the requisite pressure, I prefer to use the construction shown in Figs. 7 to 9, inclusive, or the modified construction shown in Figs. 10, 11, and 13.

Examining Figs. 7and 8, there will be found a brush-holder a, which'is fixed to or mounted on the end of the spider-arms of Fig. 1. The carbon commutator-block 3 slides radially within the brush-holder a and is electric- This inconvenience I remedy ally connected to the arm 4 of the spider by a flexible wire or cable f, one end of which is secured to the arm 4 by the binding-screw o and the other end of which is secured to the carbon brush-block 3 by means of a copper connection, preferably electroplated to the bottom of the carbon block. In order that the flexible cable f may reach the carbon brush 3, the brush-holder a is formed with the slot r. I have for convenience constructedmy brushholder at to receive two sliding carbon blocks 3. The centrifugal force caused by the rotation of the spider-arms 4 will press the carbon block 3 against the inside surface ofthe hollow commutator with the required force. The centrifugal force will act as a perfect spring and without inertia. The dimensions ofthe commutator will be such that the angular speed of the brushes will produce a pressure against the walls of the commutator of the desired value when the brushes are new. hen the brushes have been used up to a certain degree and have grown lighter in weight, the decrease in pressure will be compensated for by the introduction of metallic masses of suitable weight at the bottom of the holder at. These weights will press against the bottom of the brushes and will add to the centrifugal action by their weight. It will be desirable to build up the carbon brushes of layers-Z Z,

as shown in Fig. 9, which are glued together by a paste of small conductivity.

The brushes which I have so far described are well adapted for use when the transformer is to transform alternating currents into continuous currents; but when the transformer is totransform continuouscurrents into alternating currents I use the construction shown in Figs. 10, 11, and 13. In this construction the spider-arms 4 are connected by an annular plate J, just as the spokes of a wheel are connected by the rim. A pneumatic tube P rests within the groove in this rim J, very much as the pneumatic tube of a bicycle wheel rests within the rim of the wheel. Between any two adjacent spider-arms 4 the tube is held down on the rim by segmental plates, which it is unnecessary to show. At the extremities of the spider-arms 4 I fasten plates J. (Shown in section in Fig. 10 and in plan in Fig. 13.) These plates J are formed with preferably two brush-holders a. Inside of these brush-holders slide sockets g, in which are frictionally held the carbon blocks 3. The socket g is formed with a slot '1" for the passage of the cable f, and beneath the block 3 there is a wedge 7b, which serves to raise the block 3 with reference to the socket g when the block 3 begins to wear. By inflating the pneumatic tube to a desired degree the brushes or blocks 3 are caused to press against the commutator-segments with the desired pressure even when the brushes are not rotating and there is no centrifugal force. This enables the construction of Figs. 10, 11, and

'branched across them.

13 to be used when the brushes have to carry a large current when starting and before their centrifugal force comes into play, which is the case when direct current is transformed into alternating currents.

The starting of the recttfi t'ng-transformcr. The principal circuit connections shown in Fig. 12 have been described above. It is merely necessary to add that the wires a: u, coming from the brushes 1O 11, carry continuous current and that there is a voltmeter V The wires 00 u are connected to the wires cc u by means of a pole-changing switch X. There is an am meter A in the wire to. There is a switch I, which may either connect the field-windings of the motor M to the continuous-current leads 0; u or which may close the field-circuits of this motorin short circuit upon themselves. Finally there is a switch I connecting the alternating-current leads to the alternatingcurrent side of the transformer.

If it is desired to transform alternating current into continuous current, the pole-changing switch X is placed in its open-circuit position and the switch I is placed in the position in which itshort-circuits the field-Winding of the motor M.- The alternating currents being supplied to the transformer by closing switch I, the motor M is started by hand in making use of the special crank or key. It begins to run as an induction-motor and attains a speed-approximating synchronism. l/Vhen this approximately synchronous speed is attained, the switch I is manipulated so as to send into the field of the motor M the current which is being rectified by the brushes of the transformer. The motor then instantly synchronizes. In order to determine the direction of this continuous current, the voltmeter V is examined and the polechanging switch X is manipulated to throw the continuous current onto the line at u in the proper direction.

In order to transform continuous current into alternating currents, the switches I and X are opened, while the switch I is turned to connect the field of the motor M with the leads x u. The armature of the motor is then brought up to speedby hand and the switch X is closed. As soon as this is done the motor synchronizes, and the switch I may now be closed to send the alternating currents to line.

I repeat that while I have shown my invention as applied to a rectifying-transformer the broad features of my invention and certain of the constructions which I have shown are useful in other connections. Thus, for

gest themselves. I may, for example, use my compensating circuits as the armature-windings of polyphase generators. If it be desired to generate threephase currents each of the components of which is sinusoidal and which are accurately displaced from each other in phase by one hundred and twenty degrees, I use three of my compensating, circuits as the armature-circuits of the generator. I would take three such compensating circuits, each one of which is identical with either one of the compensating circuits described above, and I would superpose these three circuits on the armature-body in such a manner that the zero-coils of each compensating circuit are displaced from the corresponding zero-coils of the other two compensating circuits by one hundred and twenty degrees. These coils would be tapped to the mains in a manner well understood.

What I claim is 1. A body of magnetic material subjected to periodic magnetomotive forces tending to produce a complex rotary magnetic flux, provided with a magnetic shield against a component or components of such flux, substantially as described.

2. A body of magnetic material subjected to periodic magnetomotive forces tending to produce a complex rotary magnetic flux, provided with a magnetic shield against all but one component of such flux, substantially as described.

3. A body of magnetic material subjected to complex periodic magnetomotive forces, provided with a magnetic screen against all magnetic fluxes ofhigherorders,substantially as described.

4:. A body of magnetic material subjected to complex periodic magnetomotive forces, provided with a magnetic screen against all but a single two-branched sinusoidal rotating flux, substantially as described.

5. A body of magnetic material subjected to complex magnetoinotive forces, a system of conductors on the magnetic body arranged and connected to selectively act as short circuits for all electromotive forces generated therein by all but a single sinusoidal flux of two branches, and as open circuits toward electromotive forces generated by the latter, substantially as described. 6. An iron-cored transformer having primary and secondary windings, and compensating windings constituting a magnetic shield to all but a single sinusoidal flux, substantially as described.

7. An iron-cored transformer having primary and secondary windings, and compensating windings constituting a magnetic shield to all but a single two-branched sinusoidal flux, substantially as described.

8. An iron-cored transformer having primary and secondary windings, and two compensating windings sectioned in accordance with the variations of the sine and cosine respectively of a varying angle, the sections of each compensating winding being connected to form short circuits for all electromotive forces due to complex magneticfluxes and as open circuits to the electromotive forces due to a single two-branched sinusoidal flux, substantially as described.

9. An iron-cored ring or drum transformer having evenly-distributed primary and secondary windings, with two compensating windings having the number of their turns distributed in accordance with a sine law and a cosine law respectively, each forming shortcircuited multiple arc branches for electromotive forces due to complex magnetic fluxes and open multiple arc branches for electromotive forces due to a single two-branched rotating sinusoidal flux, substantially as described.

10. An iron-cored ring or dru m transform er having evenly-distributed primary and secondarywindings,andtwo compensating windings each formed of an even and like number of multiple branches closed upon themselves, the branches of one compensating winding having the number of their turns graduated in accordance with a sine law and the branches of the other compensating circuit having the number of their turns graduated in accordance with a cosine law, substantially as described.

11. An iron-cored rectifying-transformer of the ring or drum type having evenly-distributed primary and secondary windings and evenly-distributed sections of two compensating windings, the sections of one being connected in multiple and graduated in accordance with a sine law and the sections of the other being also connected in multiple and graduated in accordance with a cosine law; a commutator and brushes for rectifying the transformed currents, and a synchronous motor for rotating one with respect to the other, substantially as described.

12. An iron-cored rectifying-transformer of the ring or drum type having evenly-distributed primary and secondary windings and evenly-distributed sections of two compensating windings, the sections of one being connected in multiple and graduated in accordance with a sine law and thesections of the other being also connected in multiple and graduated in accordance with a cosine law; a commutator and brushes for rectifying the transformed currents and a two-phase synchronous motor for. rotating one with respect to the other having its armature supplied with tWo-phase currents from the terminals of the tWo sets of compensating windings, substantially as described.

13. An iron-cored rectifying-transformer of the ring or drum type for single-phase alternating currents, having an even number of evenly-distributed primary and secondary windings each closed upon itself and evenlydistributed sections of two compensating windings, the sections of one being connected in multiple and graduated in accordance with a sine law and the sections of the other being also connected in multiple and graduated in connection with a cosine law; alternating-current leads connecting with the primary winding at diametrically opposite points; a commutator and brushes for rectifying the transformed currents and a twophase synchronous motor for rotating one with respect to the other, receiving the twophase currents from the two sets of compensating windings, and provided with a magnetic shield for suppressing one rotary component of the magnetic flux in the armature and transformer-core, substantially as described.

14. A synchronous motor comprising a rotary armature, a stationary frame, and a field structure mounted to be shifted within the frame, substantially as described.

15. A synchronous motor comprising a rotary armature, a stationary frame having an annular bearing and a field structure mounted to be shifted within the bearing, substantially as described.

16. A synchronous motor comprising a rotary armature, a stationary frame having an annular bearing, a field structure mounted to be shifted within the bearing, a toothed sector on the field structure and a pinion meshing therewith to shift the field structure, substantially as described.

17. AtWo-polar rectifying-transformer provided with a commutator of more than one group of commutator-bars, whereby the synchronous speed of the brushes with respect to the commutator or vice versa can be reduced, substantially as described.

18. A two-polar rectifying-transformer provided with a commutator of more than one group of commutator-bars, in combination with a synchronous motor for driving the commutator or brushes, having as many pairs of poles as there are groups of commutatorbars, substantially as described.

19. A rectifying-transformer of a given number of pairs of poles, provided with a commutator divided into a number of groups of bars which is a multiple of this number of pairs and a synchronous motor for driving the commutator or brushes having as many pairs of poles as the commutator has groups of bars, substantially as described.

20. An iron-clad rectifying-transformer having its induced coils connected with the bars of a commutator, openings or slots in the iron mantle of the transformer and two connections carrying equal and opposite currents passing through each slot, substantially as described.

21. An'electrical apparatus comprising an iron frame, two associated sets of coils arranged in pairs, coils in the same pair carry- In testimony whereof I have signed my ing currents in opposite direction and juXtaname to this specification in the presence of posed pairs of leads tfaversing the frame and two subscribing Witnesses.

connected to the pairs of coils, whereby the MAURICE LEBLAN'O. opposite currents in the leads have no xnag- \Vitnesscs: netic effect on the frame, substantially as de; M ALBERT DELAS,

EDWARD P. MACLEAN.

scribed.

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