US3835430A - Tubular core electric transformer - Google Patents

Abstract

An electric transformer has a tubular iron core and its primary is located within the tube which can serve for secondary. In such case, the tubular iron core is short-circuited by a conductor connected to the tube extremities. The transformer may also have a secondary separate from the tubular iron core in which case the secondary has, preferably, likewise the form of a tube located within the tubular iron core and surrounding the primary. Both the primary and the secondary may consist of several turns. Such transformers are distinguished by exceptionally high values of power factor and efficiency, and are particularly suitable for heating, heat storing and energy shock absorbing purposes.

Description

United States Patent 1191 [111 3,835,430 Kocsis Sept. 10, 1974 [54] TUBULAR CORE ELECTRIC 1,606,816 11/1926 Stevenson.... 336/83 2,107,172 2/1938 Agricola 336/83 TRANSFORMER 3,305,811 2/ 1967 Toombs 336/83 [75] Inventor: Laszlo Kocsis, Budapest, Hungary 3,344,383 9/1967 Aberizk 336/210 X Assignee: Transelectro Magyar villamossagi Kulkereskedelmi Vallalat, Budapest, Hungary Filed: Apr. 5, 1972 App]. No.: 241,473

Related US. Application Data Continuation of Ser. No. 37,467, May 18, 1970, abandoned, which is a continuation of Ser. No. 774,986, Nov. 12, 1968, abandoned.

Foreign Application Priority Data Sept. 20, 1968 l-lungary..- KO 2192 US. Cl 336/83, 336/73, 336/174, 336/175, 336/212 Int. Cl. H011 17/06 Field of Search 336/83, 212, 216,73, 174,

Primary ExaminerThomas J. Kozma Attorney, Agent, or Firm-Young and Thompson [57] ABSTRACT An electric transformer has a tubular iron core and its primary is located within the tube which can serve for secondary. In such case, the tubular iron core is shortcircuited by a conductor connected to the tube extremities. The transformer may also have a secondary separate from the tubular iron core in which case the secondary has, preferably, likewise the form of a tube located within the tubular iron core and surrounding the primary. Both the primary and the secondary may consist of several turns. Such transformers are distinguished by exceptionally high values of power factor and efficiency, and are particularly suitable for heating, heat storing and energy shock absorbing purposes.

4 Claims, 12 Drawing Figures TUBULAR CORE ELECTRIC TRANSFORMER This is a continuation of application Ser. No. 37,467, filed May 18, 1970, which is a continuation of application Ser. No. 774,986 filed Nov. 12, 1968; both are now abandoned.

This invention relates to electric transformers.

As is known, in case of high secondary amperages the power factor of conventional transformers is substantially less than unity. This is due to considerable stray fields by which also the short-circuit current of a transformer is'materially reduced.

The invention aims at eliminating such inconveniences by providing a transformer which is suitable for yielding high secondary amperages at a power factor of at least 0.9 and even more.

For this purpose, the invention suggests to employ a tubular iron core with a primary therein. Viz., the basic idea of the invention is that with such tubular iron cores the flux path is the shortest and, therefore, the required exciting current the smallest. At the same time, due to its ferromagnetic nature, the tubular iron core may also serve for-secondary.

Further and closer details of the invention will be described hereinafter by taking reference to the accompanying drawings which show various exemplified embodiments of the new transformer and in which:

FIG. 1 is a perspective view showing the principal features of the invention.

FIG. 2 illustrates an equivalent electric circuit to FIG. 1.

FIG. 3 shows a perspective view of a practical embodiment of the invention.

FIG. 4 is an exploded view of a detail of FIG. 3.

FIG. 5 represents a perspective view of another exemplified embodiment of the invention.

FIG. 6 illustrates an equivalent electric circuit to FIG. 5.

FIGS. 7 to-12 show similar views of further exemplified embodiments.

Similar details are referred to by same reference characters throughout the drawings.

As is shown in FIGS. 1 and 2, the transformer has a tubular iron core made of ferromagnetic material such as iron. In the tubular iron core 20 there is a primary 22 made of electrically conductive material such as copper (Cu) and forming a primary circuit I between not specified terminals. The iron core 20 and the primary 22 are separated from one another by an insulation 24 such as mica. Moreover, the iron core 20 being of ferromagnetic material may serve for secondary as well for which purpose it is short-circuited by a conductor 26 with which it forms a secondary circuit II.

In operation, the transformer works in the usual manner. A primary ac. voltage is applied to the terminals of the circuit I whereby a secondary voltage is excited in the secondary circuit II so that a secondary current will flow through the iron core 20 and the conductor 26.

Such transformer is distinguished by a power factor of about 0.9 and is particularly suitable for heating purposes, storing of heat, and taking up high shock loads if the insulation 24 is of refractory nature as in the instant case.

A practical embodiment of the transformer according to the invention for heating purposes is illustrated in FIGS. 3 and 4. It is seen that there are a pair of tubular iron cores 20a and 20b which are electrically connected with one another at their extremities to a closed electric circuit by a pair of tubular yokes 28 and 30 made likewise of ferromagnetic material such as iron. Both yokes 28 and 30 are, in a common plane of the tubular iron cores 20a and 20b, subdivided into a pair of crescent- shaped parts 28a, 28b and 30a, 30b, respectively. FIG. 4 shows the subdivision of the tubular yoke 28. After the primary 22 with its insulation 24 has been placed in the tubes 20a and 20b as well as in suitable grooves of yoke parts 28a and 30a, the upper portions 28b and 30b of the yokes are placed on top yoke parts 28a and 28b, respectively, and bonded with them by means of e.g. welding or brasing. The tubular yokes 28a, 28b and 30a, 30b are connected with the tubular iron cores 20a and 20b in a similar manner.

Obviously, the short-circuiting conductor 26 of FIGS. 1 and 2 is formed here by the tubular yokes 28 and 30 which means that, on the one hand, there is practically no stray flux and, on the other hand, the secondary current will flow in an iron body 20a, 20b, 28, 30 which not only protects the primary 22 but also serves as a no-voltage heating means.

The exemplified embodiment illustrated in FIGS. 5 and 6 differs from the previous one in that its secondary consists of a separate winding 28 rather than of the tubular iron core 20 proper. It is made of non-magnetic but electrically conductive material such as brass so that its resistance is lower than the resistance of the ferromagnetic tubular iron core 20. Moreover, it is likewise of tubular shape and is located within the tubular iron. core 20. Thereby, the secondary current will flow close to the primary 22 on a path well defined by the secondary 28. A transformer of such special arrangement may reach a power factor of about 0.99.

FIGS. 7 and 8 show an exemplified embodiment which is distinguished from the previous one by a tubular iron core composed of axially juxtaposed annular pieces such as rings punched out of core metal sheets as if it were subdivided along planes transverse of the axial direction of the transformer. Such subdivided annular pieces are referred to by reference characters 20/1, 20/2, 20/3. The significance of such embodiment consists in that there are practically no Foucault currents (eddy currents) which would flow in an integral tubular core 20. Thus, a high transformer efficiency is obtained. Furthermore, the secondary circuit is, in the instant case, provided with terminals at which a load may be connected since a transformer of such construction already permits to take off a secondary output and is distinguished by a maximum value of the power factor.

The exemplified embodiment illustrated in FIGS. 9 and 10 shows that the transformer according to the invention may have several turns of primary and/or secondary. In the instant case, there are one pair of primary windings 22a and 22b, and one pair of secondary windings 28a and 28b, their corresponding insulations being designated by reference characters 24a, 24b and 32a, 32b, respectively, and made e.g., of rubber.

FIGS. 11 and 12 represent an exemplified embodiment which differs from that according to FIGS. 7 and 8 in that some of the annular parts of the tubular iron core are made of a material of reduced electrical conductivity. In the instant case, annular parts 20/1, 20/2, 20/3 made of a ferromagnetic material of greater conductivity such as iron pairwise sandwich annular parts 34/ l and 34/2, respectively, of lower conductivity such as cast iron or, preferably, some antimagnetic steel. Moreover, all parts /1, 34/1, 20/2, 34/2, 20/3, etc., are mutually fixed, e.g., by means of applying an axial compressive force to them exceeding the yield points of the materials employed. Hereby, a rigid and very stable structure is obtained in which the iron core proper may serve for supporting the other parts of the transformer.

It will be seen that the transformer according to the invention has the special feature of almost a complete lack of stray fluxes which is due to the primary and, possibly, the secondary being disposed coaxially inside a tubular iron core which itself may serve also for secondary if such use has special advantages as in case of 15 heating transformers. Measuring results obtained by conventional transformers and transformers according to the invention of same quality of iron cores and same values of induction as well as similar turn numbers are compared in the following table:

where values characteristic of conventional transformers have been taken for unity. It has to be pointed out that all values figuring in the table can be obtained simultaneously. However, ifidependent on the nature of use, a certain magnitude has still to beimproved, it is possible to size the transformer correspondingly at the expense of the remaining pair of values.

What we claim is:

1. In an electric heating transformer, a tubular solid iron core and a transformer primary within said tubular core and insulation within said tubular core surrounding said transformer primary; the improvement in which said tubular core is in the form of a closed loop comprised by a plurality of iron core elements electri cally conductively bonded together by welding or brazing in electrically short-circuited relation.

2. A structure as claimed in claim 1, said tubular iron core comprising a pair of tubular iron core elements disposed in a common plane and interconnected at their ends by tubular iron yokes which are divided in said plane into pairs of crescent-shaped parts.

3. A structure as claimed in claim 2, which is elongated in the direction of said tubular iron core elements, said transformer primary and insulation being continuous through one .of said yokes and emerging from said core through the other of said yokes.

4. A structure as claimed in claim 3, said yokes being semi-circular.

Claims (4)

1. In an electric heating transformer, a tubular solid iron core and a transformer primary within said tubular core and insulation within said tubular core surrounding said transformer primary; the improvement in which said tubular core is in the form of a closed loop comprised by a plurality of iron core elements electrically conductively bonded together by welding or brazing in electrically short-circuited relation.

2. A structure as claimed in claim 1, said tubular iron core comprising a pair of tubular iron core elements disposed in a common plane and interconnected at their ends by tubular iron yokes which are divided in said plane into pairs of crescent-shaped parts.

3. A structure as claimed in claim 2, which is elongated in the direction of said tubular iron core elements, said transformer primary and insulation being continuous through one of said yokes and emerging from said core through the other of said yokes.

4. A structure as claimed in claim 3, said yokes being semi-circular.

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