US687048A - Transformer. - Google Patents

Description

Patented Nov. I9, 190i.

W. S. MUUDY.

TRANSFORMER.

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UNITED STATES PATENT OFFICE.

VALTER S. MOODY, OF SCHENECTADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATICN-OF NEV YORK.

TRANSFORMER.

SPECIFICATION forming part of Letters Patent No. 687,048, dated November '19, 1901.

Application nled May 31, 1901. Serial No. 62,528. (No model.)

To @ZZ whom t may concern:

Be it known that I, WALTER S. MOODY, a citizen of the United States, residing at Schenectady, county of Schenectady, State of New York, have invented certain new and useful Improvements in Transformers, (Case N o. 1,69l,) of which the following is a specification.

This invention relates to improvements in [o the structure of potential transformers; and it consists in means for obviating the dificulties incident to the proper location of leads taken from different points of one winding for purposes of regulation.

The transformers upon which the improvements are made are of that core type which are constructed with a single set on each core of concentric primary and secondary windings, in contradistinction to the species which zo is provided With primary` and secondary windings which are alternately arranged along the core. A transformer having a single set of concentric primary and secondary windings does not require the numerous insulat- 2 5 ing-diaphragms which are essential in a transformer provided with alternating` coils. In most transformers of this type it is desirable to vary the ratio of transformation, and this is done either by changing the connections of 3o the diiferent terminals from different points of the winding or by operating multiple-point switches, which are employed when it is desired to make such changes more quickly in order to obtain voltage regulation of the system supplied by t-he transformer. It is generally necessary to superpose the primary and secondary windings upon each other in order to avoid magnetic leakage, and the secondary winding is located next the core, as it is much 4o easier to properly insulate the high-voltage primary Winding when it is on the outside. The changes iny the ratio of transformation are made by carrying the connections to leads from diiferent points of the low-voltage or secondary winding, and hitherto these leads have been taken from successive portions of the secondary winding lying beneath the primary. This has been considered the only possible way to produce the result, although 5o great diiculty has always been experienced in properly insulating the regulating-leads from the secondary and although these leads extended throughout the Whole length of the windings, where they occupied a great deal of space and increased the necessary size of the transformer. I have conceived the idea of dispensing with the leads from different points of the secondary lying beneath the primary and of winding the primary and secondary so that they occupy slightly less than the entire longitudinal winding-space about the core. In this space is located a separate or auxiliary regulating-Winding, which is not surrounded by the primary and from the outu side of which the regulating-leads can be taken withoutinterfering in anyway with the primary or the other parts of the transformer. The layers of wire in this auxiliary Winding are so short that it is frequently possible to include an entire layer between each two regu- 7c lating-leads, or7 in other words, in each step of the regulation. The location of this auxiliary winding, as described, is such that a rather high impedance existsv between it and the primary; but this is not objectionable, as it is so small a part of the entire Winding.

Furthermore, transformers provided with means for varying the ratio of transformation are generally used in systems Where there is already a relatively high reactive voltage,

and hence the impedance between this auxiliary winding and the primary is not material. XVhen the auxiliary winding is cut out,

however, the impedance is decreased, whereas formerly when portions of the main secondary were cut out for regulation the primary and the remaining turns of the secondary were unbalanced.

I have proposed several effective variations of the above-described arrangement for the purpose of reducing the reactance of the auxiliary winding while still retaining the essence of the invention; but the arrangement noted above is deemed satisfactory and is now being embodied in commercial transformers. It is perfectly obvious, however, thatin transformers of the type provided with two corelegs one half of the auxiliary Winding could be placed on one leg of the transformer at the upper end of the Winding-space and the other half of the auxiliary winding could be placed on the other leg at the lower end of the windin g-space, so as to materially reduce the reactance between the auxiliary winding and the primary.

Another variation of the arrangement within the limits of the invention is that wherein the primary and secondary windings on either leg of the core are separated into two parts and the auxiliary winding occupies a position on thelegintermediate between the separated portions of the main windings. Furthermore, in the case of transformers having two corelegs it may sometimes be sufficient to provide an auxiliary regulatingr or secondary winding on only one leg.

Of the drawings, Figure l is an elevation of the windings and core of the transformer, showing a portion of the windings and the metal casing in section; and Fig. 2 is an elevation of the transformer.

As shown in Fig. l, the secondary winding Sis mounted directly upon the core C and the primary winding P is superposed upon the secondary. These main coils may be wound as single members or they may be composed of separately-wound coils connected in series, as shown with respect to the primary coils in Fig. 2. The transformer shown is of the type wherein the core is provided with two long legs upon which the windings are mounted, half of the windings being located in the opening or winding-space O between the core-legs. The casing G is of cast-iron and is usually lled with oil to insulate and cool the parts. The process of insulating the primary is facilitated by mounting it, as shown, over the secondary, and the arrangement of the two windings with respect to each other is adopted to avoid magnetic leakage.

The ratio of transformation is changed by varying the connections of the secondary -winding to cutout different portions thereof.

It will be seen in Fig. l that the primary and secondary win dings are separated by suitable insulation I. IIitherto it has been customary to take the regulating-leads from the various points of the secondary throughout the entire Vertical length of the Winding and to carry them up between the secondary and primary to the top of the casing, where the changes and connections could be made, or to carry them farther to a multiple-point switch, where the changes could be more quickly made. There were several serious objections to this method. In the first place, it was difficult to properly bring out the leads from the secondary and to insulate them on account of the primary winding, which is mounted as close as possible to the secondary in order to prevent excessive reactance. In the second place, if this work was properly done there was necessarily a considerable valuable windingspace occupied by the regulating-leads, so that not only could the primary not be as economically disposed with respect to the secondary, but the size of the completed windings was materially increased. A third serious difficulty would sometimes arise in case any of the connections of the regulating-leads with the secondary beneath the primary bccame injured in transportation or by the assemblage of the coils about the core or within the casing. In each case it was necessary to take the entire apparatus apart in order to repair the defect.

By constructin g transformers in accordance with this invention these difficulties are entirely obviated and the leads can be conveniently attached to the winding without the necessity of carrying them between the primary and secondary. Both windings are mounted upon the legs of the core, as usual, except that they occupy less space than the full length of the winding-space, so that, for example, one-tenth of the space is left, preferably, at the top of the core-legs, as shown. Upon the legs are mounted separate auxiliary windings which fill the remaining windingspace and extend from the core laterally to occupy the same lateral space which is filled at the lower portions of the legs by both the primary and secondary windings, so that the entire transformer-windings are symmetrically disposed. These separate windings are connected with the secondary winding, which connection may be made in any desirable way, such as that between the different scctions of the secondary when the secondary is divided into sections. Thus the exterior' of the separate winding is not surrounded by the primary and the regulating-leads may be taken from the outer surface of the separate winding without in any way interfering with the primary or the main secondary. These leads may be carried, as usual, to any suitable connection block-support in the top of the casing or to an exterior multiple-point switch, as desired. Then the entire auxiliary winding is in circuit, there will be some impedance between it and the primary; but, as before stated, it is so small a part of the entire winding that this is not objectionable.

When the entire auxiliary winding is cutout, the main windings will be symmetrically disposed and there will be no excessive reactance, as was formerly the case when portions of the main secondary were cut out to regulate the voltage of the system supplied by the secondary.

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

1. In a transformer, the combination with the core, of two superposed windings thereon which occupy less than the total windingspace, and a separate auxiliary regulatingwinding located in the remaining windingspace and connected with the inner winding, but not surrounded by the outer winding.

2. In a transformer, the combination with the core, of two superposed windings thereon which occupy less than the total longitudinal winding-space, and a separate auxiliary regulating-windin g located in the remaining windV ICO IIO

ing-space, connected with the inner winding, and occupying the same lateral space as both main windings.

3. In a transformer, the combination with the core, of two superposed windings thereon which occupy less than the total longitudinal winding-space, a separate auxiliary regulating-winding mounted on the core in the remaining longitudinal space and connected to the inner winding, and a plurality of leads from the exterior of said auxiliary winding.

4. In a transformer, the combination with a core having two legs, of two superposed windings mounted on each leg to occupy less than the total longitudinal winding-spaces, and two separate auxiliary regulating-coils mounted on the respective core-legs in the remaining longitudinal spaces and connected to the inner winding on each leg respectively.

5. In a transformer, the combination with the core, of a secondary winding mounted thereon, and a primary winding mounted over the secondary winding, said windings occupying less than the total longitudinal winding-space about the core, and a separate auxiliary regulating-winding connected with the secondary, mounted on the core in the remaining winding-space, and divided into sections by a plurality of leads extending from its outer surface and connected to dierent points of its length.

6. In a transformer, the combination with a core having two legs, of two superposed windings mounted on each leg, one at least of the sets of windings occupying less than the total longitudinal winding-space, and at least one separate auxiliary regulating-winding mounted in the remaining longitudinal winding-space and connected to the inner winding.

In witness whereof I have hereunto set my hand this 28th day of May, 1901.

WALTER S. MOODY.

Witnesses:

BENJAnIN B. HULL, MARGARET E. WOOLLEY.

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