US1336894A - Electrical transformer - Google Patents

Description

S. Z. DE FERRANTI.

ELECTRICAL TRANSFORMER.

APPLICATION FILED FEB. 1, 19m.

1,336,894. v Patented Apr. 13, 1920.

S. Z. DE FERRANTI.

ELECTRICAL TRANSFORMER.

APPLICATION FILED FEB. I. 19I6.

' 1,336,894. Patented Apr. 13, 1920.

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ECTRICAL TRANSFORMER.

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ELECTRICAL TRANSFORMER.

APPLICATION FILED FEB. 1., 1916..

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Attorney's.

STATES PATE T OFFICE.

\ SEBASTIAN ZIAKI DI: FERRANTI, OF BASLOW, ENGLAND.

ELECTRICAL TRANSFORMER To all whom it may concern:

Be it known that I, SEBASTIAN ZIANI on FEBRANTI, 'of Baslow, in the county of Derby, England, a subject of the King of Great Britain and Ireland, have invented certain new and useful Improvements in and Relating to Electrical Transformers, of which the following is a specification.

The invention relates to electrical transformers;

When an excessive current due to a short circuit or otherwise passes through the windings of a transformer, very heavy mechanical stresses are produced due to repulsion, as is explained below, and the primary object of the present invention is to provide an improved construction better adapted than heretofore for withstanding such stresses.

It is well known that electric currents or their conductors experience forces which tend to move them into positions where the currents will link the maximum magnetic flux. Like currents therefore are mutually attracted since conjointly they increase the flux, and unlike currents mutually repel. The mechanical force of attraction or repulsion is proportional to the increased flux linked with the currents for a given small movement of the conductor.

The currents in the pr mary and'secondary windings of. a transformer so nearly balance and the coils are so close together that there is very little linkage of magnetic flux in the undisturbed condition of the coils, what linkage there is being that which finds its way between the by paths external to the transformer-core.

' If, however, the coils be slightly displaced mutually this linkage is much increased and it follows that forces operate tending to throw the coils still farther apart.

The repulsion is much heavier if the outer coils are longer than the inner as convenience of manufacture may sometimes require, but there is some repulsion even when the coils are of the same length.

Under normal conditions the repulsive forces between primary and secondary coils are within bounds that can be easily dealt with, but under -,excessive currents these forces may become very large. There is hardly any limit to the currents that may flow in the case of a large well regulating transformer, the limit being mainly a matter of the power in the generating station,

Specification of Letters Patent. Patented Apr, 13, 1920.

Application fled. February I, 1916. Serial No. 75,614. V

With this object the invention consists broadly in a transformer in which the winclrugs are held against their seatings by resilient members so that no reversal of thrust takes place on the occurrence of an QXCGSSIVB current.

The invention consists more specifically in a transformer in which the windings are formed in units with interposed springs or the like to thrust the windings against their seats.

The invention also consists in the improved transformers hereinafter described or Indicated.

Referring now to the accompanying drawings:

igure 1 shows a side elevation partly in sect on of one form of the invention;

li g. 2 being a corresponding plan, and

r g. 3 an end elevation.

Fig. 4; shows a section through the line C-D of Fig. 1, showing the disposition of the springs, while Fig. 5 shows a section through the line EF in Fig. 4.

Fig. 6 shows a detail view of the springs in their compressed state;

Big. 7 shows an arrangement springs;

Fig. 8 shows an arrangement of springs with sectional bearing plates, while Fi 9 shows a cross-section through the line H of Fig. 8.

Figs. 10 and 11 are details showing the method of fastening the bearing plates to the coils;

Fig. 12 shows a method of applying my improvements to the heavy winding of a transformer.

Fig. 13 shows my improvements as applied to heavy conductors.

In carrying the invention into efi'ect according to the illustrative form shown, a laminated core, a, a is built up in any suitable manner and secured by bolts, 7), the windings, 0, (Z, encircling those legs of the core formof double tors.

ing opposite sides of the rectangle. The heavy windings c are arranged next to the core and are surrounded by the fine windings d, with the usual intervening insulation e. About the middle of their length the -fine windings are divided into two parts or units as shown, by volute springs, h, bearing on plates f, and forcin theunits apart and against packing i, i. he packing i, i abuts against the core, the channels, j, y, and the channel pieces, I, l, which are secured to the channels by bolts, m.

In Figs. 4 to 7 the arran ement of the springs is shown in detail. rojections, 'n, are formed on the bearing plates, f, with which the springs h engage as shown in Fig. 5. These projections are arranged alternately on the upper and lower plates, so that the position of adjacent springs is reversed as shown in Fig. 6, in which the springs are shown in their compressed state.

In Fig. 7 an alternative arrangement to that previously described is illustrated. In this case the springs are arranged opposite to one another on the top and bottom bearing plates the smaller ends of the springs bearlng against a plate or washer o, inserted therebetween.

In 'Figs. 8 to 11, a somewhat modified arrangement of bearing plate is shown. In this example the plates are arranged in sections, p, two springs being disposed on each section. The edges of the sections are also upturned to embrace the windings as shown in Fig. 9. Bindings, g, shown in Figs. 10 and 11 disposed across the gaps between the sections,-pass around the windings and secure the sections in position.

The springs in the above arrangements may be secured to the bearing plates or sections by being electrically welded thereto.

Itwill thus be seen from the above ar rangements that the iron of the magnetic circuit is-utilized to take end thrust due to repulsion, and in some cases I may provide additional bolts for this urpose.

In Fig. '12 is illustrate the application of my improvements to heavy conductors such, for example, as one of the windings of a transformer. In this arrangement pairs of wedges, s, forced apart by spiral springs 25, are dis osed between the adjacent conducgo-aeting with the wedges are correspondingly inclined parts, u, secured to the plates by electric welding or otherwise.

The pressure of the springs thus acts'at a mechanical advantage forcing the conductors apart, while any force tending to cause the conductors to approach acts at a mechanical disadvantage owing to the friction of the wedge-shape surfaces. The windings are thus held rigidly against their abutments. I

In Fig. 13 an arrangement is shown in which forked springs, 1", are inserted between divided heavy conductors or adjacent heavy conductors. In this case owing to the type of springs employed the conductors or parts of conductors may approach close to one another as the springs in the compressed state lie practically flat.

In the constructions of transformers above described the spring elements are disposed between sections of the transformer coils which tend'to move apart by repulsion, explained above, and rigid abutments are provided to withstand the combined stresses due to this repulsion between the coil sections and due to the force exerted by the spring elements. By this means no reversal in the direction of either thrust takes place even on the occurrence of an excessive current. Further, in the event of a short circuit taking place, since the resulting thrust due to repulsion acts in conjunction. with that due to the springs, the effect is simply to increase the load upon the end abutments without movement of the coils taking place. The springs thus serve automatically to com pensate for any axial change in the dimensions of the windings due for example to the shrinkage of the insulations, but are never compressed by the repulsion act of the coil sections.

Any other resilient member or members may be substituted for the springs described, so long as the windings are held rigidly against their seats.

The invention may also be applied to three-phase or other transformers of many different patterns.

Having now fully described and ascertained my said invention and the manner in which it is to be performed I declare that what I claim is 2- 1. The combination in an electric transformer of a closed circuit iron core, end supporting members rigid with said core, a coil abutting directly against and supported by one of said supporting members a second coil abutting directly against and supported by a second supporting member and resilient means inserted between the coils, thrusting the coils in the same directions as those in which the resultant axial forces act.

2. The combination in an .electric transformer of a closed circuit iron core, end supporting members rigid with said core, primary coils axially supported on said core by said supporting members and in close proximity thereto, secondary coils concentric with said primary coils abutting directly against and axially supported by said supporting members a division in one of the coils and resilient means inserted in the division.

3. The combination in an electric trans former of a closed circuit iron core, end supporting members rigid with said core, a

coil abutting directly against and supported directly against the end supporting member by one of said supporting members a second a second end supporting member rigid with coil abutting directly against and supported said core, a second c011 abutting directly by a second supporting member, a division against the second end supporting member 5- betWeen coils and resilient means inserted in a division between the coils and resilient 15 the division to maintain the windings 0011- means in the division. stantly against their seats. In testimony whereof I have aflixed my 4. The combination in an electric transsignature.

former of an iron core, an end supporting 10- member rigid with said core, a coil abutting SEBASTIAN ZIANI DE FERRANTL-

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