US1717347A - Transformer - Google Patents

Description

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G. CAMILLI TRANSFORMER June 11, 1929.

Filed Oct. 10, 1928 2 Sheets-Sheet bHm f 4 i lrno cam i I I i y H is AttO1 11 ey.

lvwvevwtora the ma netic losses in these parts maybe coni Patented June 11, 19 29.

UNITED STATES 1,111,347 PATENT OFFICE.

GUGLIELMO CAMILLI, OF PITTSFIELD, MASSACHUSETTS, ASSIGNOR T0 GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

TRANSFORMER.

Application filed October 10, 1928. Serial No. 311,639.

My invention relates to transformers and more particularly to transformers having concentric cylindrical windings. When a transformer is in operation, the main mag-- netic flux is substantially confined to the core. The action of the primary and secondary Currents also produces a leakage fluxbetween the two windings. This leakage flux, after flowing between the windings, returns through the easiest path which it can find and the return path for a large part of the leakage flux often includes magnetic material near the core and windings such as the core clamping structure and the metal casing in which the transformer may be enclosed. The-flux in these adjacent magnetic parts results in magnetic losses and decreased efficiencyof the transformer and it is the general object of the invention to provide an improved arrangement for controlling and reducing the external leakage flux and the ma netic losses caused by it.

he invention will be better understood from the following description taken in connection with the accompanying drawings in which Fig. 1 is a perspective view of a shell type transformer provided with means for reducing the external leakage flux; Fig. 2 is a similar view of a core type transformer; Fig. 3 is a similar View of a three phase core type transformer and Fig. 4 is a view of a transformer like that shown in Fig. 1- but with a different arrangement of windings.

Like reference characters indicate similar parts in the different figures of the drawings.

The transformer shown in Fig. 1 is of the shell type with a magnetic core 10 having a central winding leg and two outer legs joined at their ends by yokes. The central winding leg is surrounded by the two windings-11 and 12. The main magnetic flux is substantially confined to the core. The currents in the two windings produce a leakage flux through the space between them and returning through the easiest path which it canv find. The return path for a considerable part of the leakage flux often includes magnetic material outside of the core and windings. This magnetic material may include the core clampin structure, the metal casing which may enc ose the transformer and other adj acent magnetic parts. Under these conditions,

siderab le so as to reduce appreciably the efficiency of the transformer. These losses appear as heat, too, and provision for dissipat mg this heat in addition to that from the transformer itself must be madeor excessive temperatures may result.

As shown in'Fig. 1, the leakage flux is largely. prevented from leaving the space between the two windings and reaching adj acent magnetic material by conductive members 13. con nected by conductors 14 to form closed circuits close to the ends of the windings and a in front of both ends of the space between the windings. There are four of the conductive members 13, two at each end of the outer winding and extending along and close to the ends of this winding on'opposite sides of the core. The ends of each member 13 are connected by conductors 14 tothe ends of the member 13 which is at the same end of the winding 1.2 and on the opposite side of the core, the conductors 14 extending around the outer edge of the core to avoid a short circui ted turn around the central winding leg of the core. It is apparent that no substantial amount of leakage flux can leave the space between the two windings except through the core under the conductors 14. Any magnetic material near the core and windings is thus efiectively shielded and protected. It

tained in most cases if the conductive members 13 extend along the outer face of the winding 12 and near its ends, the members 13 being as close to the winding as is-practicable with the necessary insulation between them. The conductive members 13 and the conductors 14 connecting them around the outer edge of the core are shown in Fig. 2 as applied to a core type transformer. The core 10 has two winding legs, each surrounded by two windings" 11 and 12. This core has only a single opening and each set of windings passes through the core only once so that only one member 13 is necessary at each end of each of the outer windings 12, the two ends of two windings 11 and 12. The set of windings V,

on the central winding leg passes through the core twice so that two members 13 connected by conductors 14 are necessary at each'end of this set of windings. The set of windings on each of the outer winding legs passes through the core only once sothat only one member 13 with its ends connected by a conductor 14 is necessary at each end of each of these sets of windings.

The transformer shown in Fig. 4 is similar to that shown in Fig. 1 except that the winding 11 is formed in two concentric spaced sections. The-winding 12 is interposed concentrically between the two sections of the winding 11 and spaced from each of those sections. With this arrangement, the leakage flux is induced in the two spaces inside and outside of the winding 12 and between that winding and the two sections of the winding 11 and it isinducedin opposite directions at any instant in these two spaces. Not all of the flux in either of these spaces, however, may return through the other space. Some of the flux tends to leave the windings and returnthrough the easiest outside path as has already been explained. The conductive members 13 connected by the conductors 14 largely reduces the outer magnetic" field as in the case of the transformer shown in F ig. 1. Some' of the magnetic fluxv also tends to return inside of the inner section of the winding 11 and much of this flux would enter the central winding leg crosswise of its laminations where it would cause excessive losses. Conductive members 15 are therefore provided near both ends of the inner section of the winding 11, the twomembers 15 at each end being connected into a closed circuit by conductors 14 passing around the outer edge of the core. This closed circuit will obviously prevent any substantial amount of flux from returning inside the inner section of the winding 11 so that nearly all the leakage flux will be confined to a path through the two spaces next to the winding 12.

The inventionhas been explained by describing and illustrating its application to various forms of transformers and it will be apparent that various further changes andmodifications may be made without de arting from the scope of the invention as de med in the appended claims.

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

1. A transformer including a core'having a win-ding leg, two spaced concentric windings surrounding said winding leg, and a conductive member extending along and close to an end of the outer of said windings, the ends of said conductive member being connected to form a closed circuit in front of the space between said windings.

2. A transformer including a core having a winding leg, two spaced concentric windings surrounding said winding leg, and a conductive member extendingalong and close to an end of the outer of said windings on each side.

of said core, said conductive members being connected around the outer edge of said core to form a closed circuit in front of the space between said windings.-

3. A transformer including a core having a winding leg, two spaced concentric windings surrounding said winding leg, and a conductive member extending along and close to each end of the outer of said windings on each side of said core, said conductive members being connected around the outer edge of said core to form a closed circuit in front of each end of the space between said windings.

4. A transformer including a core having a winding leg, two concentric windings,

GUGLIELMO CAMILLI.

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