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Publication numberUS3792396 A
Publication typeGrant
Publication dateFeb 12, 1974
Filing dateMar 20, 1973
Priority dateApr 7, 1972
Also published asDE2315522A1, DE2315522B2
Publication numberUS 3792396 A, US 3792396A, US-A-3792396, US3792396 A, US3792396A
InventorsPanu V
Original AssigneeStroemberg Oy Ab
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Voltage transformer
US 3792396 A
Abstract
A voltage transformer comprising a hollow support insulator within which is arranged a main insulator and associated with this, a magnetic circuit, at least one primary winding and at least one secondary winding, together with necessary conductors. The main insulator is of tubular form and made up of a number of metal foil tube elements located inside each other in such a manner as to overlap each other partially but not completely, with insulator elements of tubular form arranged between them. A first winding (either a primary or a secondary winding) is located around the main insulator and a second winding (either a secondary or a primary winding) is located inside the main insulator approximately opposite to said first winding. The magnetic circuit comprises two separate core sections, one of which extends from the surface of the main insulator, enclosing the first winding, at least approximately to the other end of the main insulator and the other of which extends from the surface of the main insulator, enclosing from inside the second winding, to the said other end of the main insulator where it meets the other end of the first core section.
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Description  (OCR text may contain errors)

Panu

[451 Feb. 12,1974

l 54 l VOLTAGE TRANSFORMER [75] Inventor: Vaino Tuure Kalevi Panu, Vaasa,

Finland [73] Assignee: Oy Stromberg AB, Vassa, Finland 22 Filed: Mar. 20,1973

[21] Appl. N0.: 343,147

[58] Field of Search. 336/69, 70,84, 173, 174, 175,

[56] References Cited FOREIGN PATENTS OR APPLICATIONS 904,761 11/1945 France 336/174 726,194 10/1942 Germany 336/70 839,662 4/1939 France 336/70 Primary ExaminerThomas .l. Kozma Attorney, Agent, or Firm-Young & Thompson [57] ABSTRACT A voltage transformer comprising a hollow support insulator within which is arranged a main insulator and associated with this, a magnetic circuit, at least one primary winding and at least one secondary winding, together with necessary conductors. The main insulator is of tubular form and made up of a number of metal foil tube elements located inside each other in such a manner as to overlap each other partially but not completely, with insulator elements of tubular form arranged between them. A first winding (either a primary or a secondary winding) is located around the main insulator and a second winding (either a secondary or a primary winding) is located inside the main insulator approximately opposite to said first winding. The magnetic circuit comprises two separate core sections, one of which extends from the surface of the main insulator, enclosing the first winding, at least approximately to the other end of the main insulator and the other of which extends from the surface of the main insulator, enclosing from inside the second winding, to the said other end of the main insulator where it meets the other end ofthe first core section.

14 Claims, 1 Drawing Figure Bi w PATENTEDFEBI2I974 VOLTAGE TRANSFORMER This invention concerns a voltage transformer comprising a hollow support insulator within which is arranged a main insulator, a magnetic circuit associated with this, at least one primary winding and at least one secondary winding, togetherwith necessary conductors.

ln pin core type voltage transformers the core con sists of a ferromagnetic pin onto which the secondary winding is wound in the form of a long cylinder. The main insulation which is tube shaped is fitted over the secondary winding and carries the cylindrical primary winding. The magnetic circuit is closed across an air gap which means that the equivalent air gap of the magnetic circuit is relatively long. A large iron crosssectional area and/or a large'number of winding turns are necessary in order to obtain sufficiently high offload inductance. The dimensions of the active parts of the transformer and therefore the material costs are high. The potential, during high speed voltage variation phenomena, is distributed in a non-linear fashion in the longitudinal direction of the primary winding owing to the large earth capacitance, necessitating more insulation between the upper turns than elsewhere in the winding.

The purpose of the invention is to eliminate these aforementioned disadvantages.

The voltage transformer in accordance with the invention is mainly characterised in that the main insulator is of tubular form and made up of a number of metal foil tube elements located inside each other in such a manner as to overlap each other partially but not completely, with insulator elements of tubular form fitted between them, in that at least one first winding (either a primary or a secondary winding) is located around the main insulator and at least one second winding (either a secondary or a primary winding) is located inside the main insulator at least approximately opposite to the said first winding and in. that the magnetic circuit comprises two separate core sections, one of which extends from the surface of the main insulator, enclosing the first winding, at least approximately to the other end of the main insulator, and the other of which extends from the surface of the main insulator, enclosing from inside the second winding, to the said other end of the main insulator where it meets the other end of the first core section.

The invention is described in more detail in the following with reference to the attached drawing. The drawing shows a cross-section of one embodiment of the voltage transformer in accordance with the invention.

The main insulator tube 1 of the transformer has a length 2H-l-H, where H a the shortest permissible distance over which the voltage can be distributed in the axial direction of the support insulator, and H the height of the yoke through which the insulator tube passes. The main insulator tube 1 is made up of cylinders of metal foil 11 of mutually equal length H+H' located inside each other and thin insulating cylinders 12 of mutually equal thickness and greater length than the foil cylinders 11, lcoated between the aforementioned metal foil cylinders. At one end of the main insulator tube 1, the ends of the metal foil cylinders are located at a distance H/m further away from the midpoint of the main insulator tube 1 and correspondingly at the other end, the same distance nearer to the midpoint of the main insulator tube 1 than the end of the next metal foil cylinder inside, where m the number of insulating cylinders 12.

A primary winding 5 is wound coaxially to the main insulator tube 1 over a distance H, beginning from one end of the main insulator tube 1, in such a manner that the ends of the metal foil cylinders 11 are at the same level as the primary winding 5, and on the same side of the main insulator tube 1 as the primary winding 5 in the radial direction.

A secondary winding 4 is wound, level with the primary winding 5 in the axial direction, but, in the radial direction, on the opposite side of the main insulator tube 1. One half 2,2,2" of the magnetic circuit 2,3,6

extends in one continuous ferromagnetic section from the middle of the main insulatortube 1, from the surface of the tube, around the secondary winding 4 and I the bottom edge of the main insulator tube 1 to the end of the primary winding 5 which is at earth potential, and is thus completely at approximately earth potential.

The other half 3,6 of the magnetic circuit 2,3,6 comprises a magnetic column 6, electrically insulating in the longitudinal direction, which extends from the lower end 14 of the primary winding 5 which is at earth potential, to the high voltage end, and a yoke 3 which extends from the high voltage end 15 of the primary winding 5 to the surface of the middle section of the main insulator tube 1 on the same level, but at the other side of tube 1 in a radial direction, than the half 2 of the magnetic circuit which is at earth potential. A magnetic circuit which encloses the primary and secondary windings 5, 4 and that section of the main insulator tube 1 located between them is thus formed, the circuit being broken by the main insulator tube with an air gap whose length is the insulation thickness.

Core 2,3,6 together with windings 5, 4 and main insulator tube 1 is located within a hollow support insulator 7 in such a way that the axis of the main insulator tube 1 is parallel to the axisof the support insulator 7 and that the end of the main insulator tube 1 where all the ends of the metal foil cylinders 11 are on the outer surface is completely within the support insulator 7.

All the active parts of the transformer are thus located within the hollow support insulator 7. The ferromagnetic inner column 2 which is at earth potential is provided with flanged ends 2" and functions as a reel body for the secondary winding 4 which has the form of a cylinder. The main insulator tube 1 is wound over the cylinder made up of the ferromagnetic inner column 2 and the secondary winding 4 in such a manner that the lower end of the innermost metal foil cylinder is on a level with the lower end of the secondary winding 4 and the end of the outermost metal foil layer 11 is opposite to the upper end of the secondary winding 4. The lower end of the main insulating tube 1 is therefore composed of filler insulation 13 in order that the primary winding 5 can be wound onto a base having the form of a tube of constant diameter. The turns of the primary winding 5 are uniformly distributed over the distance H and the distribution of potential is linear.

Over the primary winding 5, is located'a cylindrically shaped magnetic tube 6 which is electrically insulating in the longitudinal direction, the upper end being galvanically connected (point 16) to the upper end 15 of the primary winding 5 and the lower end being at earth potential through conductors 10,21,17. The ferromagnetic yoke 3 which is wholly at the potential of the upper end of the primary winding 5 is located between the upper end of the electrically insulating tube 6 and the outer surface of the middle section of the main insulating tube 1. The main insulating tube 1 passes through the yoke 3, thus breaking the magnetic circuit 2,3,6 with an air gap whose length is the insulating thickness. The effect of the air gap on the characteristics of the magnetic circuit 2,3,6 can be decreased by increasing the height H of the yoke.

Differing from the embodiment described above, but within the scope of the invention, the positions of the primary and secondary windings can be interchanged, said electrically insulating magnetic tube 6 then being located inside the main insulator 1.

It is not necessary for the core section 3,6 to have the shape of a coaxial ring, but it can also have the form of, e.g., a column. The core section 2 could be located around the main insulator and the first winding. The core section 2" need not be provided with flanges, and it could also extend inwards (in the case where the primary winding is located inside the main insulator).

What we claim is:

1. A voltage transformer comprising:

a. a hollow support insulator;

b. a main insulator having tubular form and being arranged within said support insulator and being made up of a number of metal foil tube elements located inside each other in such a manner as to overlap each other at least partially, and of a number of tubular insulator elements arranged between said metal foil tube elements;

c. at least one first winding arranged coaxially around said main insulator;

d. at least one second winding arranged coaxially inside said main insulator at least approximately opposite to said first winding;

e. a magnetic circuit comprising a first and a second core section, said first core section extending from the outer surface of the main insulator, enclosing from outside said first winding, at least approximately to one end of said main insulator, said second core section extending from the inner surface of said main insulator, enclosing from inside said second winding, to said end of said main insulator where it meets one end of said first core section; and

f. a number of conductors interconnecting the different parts of the transformer.

2. A voltage transformer as claimed in claim 1, wherein the metal foil tube elements are of mutually equal length 3. A voltage transformer as claimed in claim 1,

wherein the insulating elements of tubular form are of mutually equal length and are longer than the metal foil tube elements.

4. A voltage transformer as claimed in claim 1, wherein the metal foil tube elements and the insulating elements are of cylindrical shape.

5. A voltage transformer as claimed in claim 1, wherein the metal foil tube elements are in mutually equally spaced steps and the insulating elements are also in mutually equally spaced steps.

6. A voltage transformer as claimed in claim 1, wherein the insulating elements are of mutually equal thickness.

7. A voltage transformer as claimed in claim 1, wherein the ends of the tube elements overlap in those parts of the main insulator which are located outside the core in the axial direction of the main insulator.

8. A voltage transformer as claimed in claim 1, wherein the first winding and the second winding are in the shape of cylindrical rings located one inside the other.

9. A voltage transformer as claimed in claim 1, wherein the inner part of the second core section is of cylindrical shape and is provided with a groove on which the second winding is wound.

10. Avoltage transformer as claimed in claim 1,

wherein the first core section has the shape of a cylindrical ring and is provided with an inside groove for the first winding.

11. A voltage transformer as claimed in claim 1, wherein the axial dimension of the core sections is greater than that of the windings.

12. A voltage transformer as claimed in claim 1, wherein the first core section comprises a yoke designed to fit onto the main insulator and a column connected to it, which is located at least approximately opposite to the first winding in the axial direction and is electrically insulating in the axial direction.

13. A voltage transformer as claimed in claim 1, wherein the primary winding comprises several coils located above each other in the axial direction.

14. A voltage transformer as claimed in claim 1, wherein the first core section surrounds the main insulator tube and the first winding as a coaxial ring in such a manner that one of its ends is at least approximately opposite to one end of the main insulator tube in the axial direction, and the second core section includes an inner part designed to fit at least approximately against the inner surface of the insulator tube and the second winding, and an outer part ending at said end of the main insulator tube and terminating outwards in a flange-type structure.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
DE726194C *Oct 11, 1938Oct 8, 1942Siemens AgRegelbarer Hochspannungstransformator
FR839662A * Title not available
FR904761A * Title not available
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US4032837 *Feb 10, 1976Jun 28, 1977Oy Stromberg AbCurrent transformer
US4060759 *Oct 6, 1975Nov 29, 1977Oy Stromberg AbTube-insulated shell-core current transformer
US4088953 *Nov 15, 1976May 9, 1978The Reluxtrol CompanyEddy-current test probe utilizing a combination of high and low reluctance materials to optimize probe sensitivity
US5504419 *Apr 2, 1993Apr 2, 1996Moser-Glaser & Co. AgRod-core current transformer
US5587695 *Aug 8, 1994Dec 24, 1996Zellweger Luwa AgMeasuring transformer for solid-state electricity meters
Classifications
U.S. Classification336/69, 336/212, 336/178, 336/84.00R, 336/173
International ClassificationH01F30/00, H01F38/26, H01F38/24, H01F38/22
Cooperative ClassificationH01F38/26
European ClassificationH01F38/26