FR2787625A1 - Transformer electromagnetic protection element having lower circular section with central hole and upper circular enclosing section with varnished inner/outer face area and outer soldered wire connection. - Google Patents

Abstract

The electromagnetic protection element has a lower circular section (1) with a central hole (3) on its base wall (4). An upper circular section (2) encloses the first section. The upper and lower parts of the two sections are varnished on the inner and outer face (5). A wire (13) is soldered to the upper circular section near to the lower circular section edge.

Description

The invention relates to a transformer element as well as to a

  transformer comprising said element.

  The invention also relates to a method of manufacturing said element.

  Transformers are static electromagnetic induction devices, which transform an alternating voltage and current system into one or more other voltage and current systems similarly

  frequency, but generally of different value.

  A transformer does not have an ideal characteristic; permeability

  magnetic of the material used is not infinite, there is a cycle of hysteresis.

  The non-linearity of the B-H curve of the material, the leakage self, the stray capacitance, etc., are the cause of electromagnetic interference and therefore

  the origin of high harmonics which add to the line current.

  Thus, the current is transformed into a train of pulses.

  These electromagnetic disturbances, in particular the stray capacitance, are reduced, in the prior art, by the action of a screen between the windings. It is also known in the state of the art that the addition of an electrostatic screen between primary and secondary, connected to the ground of the electronic equipment and to the ground, makes it possible to better separate the user (corresponding

  at the secondary) of the high voltage source (corresponding to the primary).

  This is important since, under certain circumstances, the current

  electric, even at low voltage, can be the source of serious accidents.

- TT ..

  The document FR-2-664 088 describes a symmetrical transformer, for transmission equipment, comprising a primary, a secondary and an electromagnetic screen integrated between the primary and the secondary of which it is

galvanically isolated.

  The transformer primary is split into two interconnected concentric windings between which the secondary is sandwiched and the electromagnetic screen is split into two interconnected elements respectively

  inserted between one of the concentric windings of the primary and the secondary.

  Document FR-2-683 671 describes a fixed induction device comprising cores in which magnetic circuits are created, a first coil encircling the cores and the second coil also encircling

the kernels.

  The apparatus also includes first electrostatic screens disposed between the first coil and the second coil and second electrostatic screens disposed between the cores and the first and second coils and covering all the surfaces of the cores which face the first and second

winding.

  The document FR-1-538 339 describes electrostatic screens in particular for

toroidal transformers.

  Document FR-2-226 734 describes a transformer provided with magnetic screens. Document FR-2-412 922 describes a transformer comprising a primary winding having two terminals, a secondary winding having two terminals and a magnetic core combined with the primary winding and the secondary winding, the transformer comprising a static screen placed between primary and secondary, so as to limit bothersome radiation. Document FR-2-389 209 describes a transformer provided with electrostatic screens between its windings, screens constituted by a flat spiral covered with varnished conductive wire wound around the carcass of the transformer. Document FR-2-399 108 describes a transformer comprising an electrostatic screen between the primary winding and the secondary winding, a

  end of the screen being connected to the ground potential, on the primary side.

  Document FR-2-468 965 describes an electromagnetic interference shielding structure comprising thin films forming alternating layers of metals having relatively high conductivity and metals having relatively low conductivity so as to combine the effects of reflection and absorption to maximize the attenuation

produced by the structure.

  The transformer structure which is the subject of the present invention makes it possible to significantly reduce the stray capacitance and provides reinforced protection.

  of the user for high dielectric voltages.

  To this end, the invention relates, according to a first aspect to an electromagnetic protection element, intended to be associated with a transformer comprising, in combination: - a lower shell provided with a hole passing through a skirt on its bottom wall annular extending from said bottom wall; - An upper shell provided with a hole traversing on its bottom wall an annular skirt projecting from said bottom wall; - The upper shell being nestable, over part of the height of its annular skirt on the lower shell; varnishes on each of the two faces of the bottom walls of the shells around the holes passing through a wire welded to the upper shell, in the vicinity of its lower free edge,

  so that the weld electrically connects the two shells.

  The through holes are of substantially the same diameter and placed facing one another when the shells are fitted. The shells are of symmetry of revolution around a central axis relative to

through holes.

  The shells are made from a material chosen from the group comprising

copper, copper alloys.

  The invention relates, according to a second aspect, to a transformer provided with an electromagnetic protection element as defined above, the

  coil was inserted between the shells.

  The invention relates, according to a third aspect, to a method of manufacturing a protective element as defined above, the method comprising the steps of: - shaping by pressing, stamping, stamping of a shell superior; - shaping by pressing, stamping, stamping of a lower shell; from a strip of conductive material such as copper or an alloy of

copper.

  The method includes a step of drilling through holes

  after the formation of the shells.

  In another embodiment, the through holes are drilled before the

shaping of shells.

  In another embodiment, the drilling and the forming of the shells are

substantially simultaneous.

  The method comprises the subsequent stages of varnishing on the field of the through holes and around said holes on each face of the bottom wall.

shells.

  The varnishing is carried out on an annular sector around the through holes. The diameter of the annular sector is of the order of twice the diameter of the

through holes.

  The method comprises a step of welding a wire on the upper shell, in the vicinity of its lower free edge, so as to electrically connect the

two shells.

  Other aspects and advantages of the invention will become apparent during the course of the

  following description of an embodiment, description which will be made in

  referring to the appended drawings in which: - Figure 1 is a perspective view of an upper shell of the transformer element according to the invention; - Figure 2 is a top view of the lower shell of the transformer element according to the invention; - Figure 3 is a perspective view of the two upper and lower shells after assembly; - Figure 4 is a diagram of the upper shell assembly process

and lower.

  In the following text, the dimensions are given for information only.

  The lower 1 and upper 2 shells can be made of copper or

annealed copper alloy.

  The lower shell 1, in an indicative embodiment, at a height of approximately mm, an internal diameter at its base D1 of 14.6 mm more or less 0.2

  mm and a greater internal diameter D'l of approximately 15 mm.

  The upper shell 2, in said embodiment, then has a height of approximately mm, an internal diameter at its base D2 of 14 mm more or less 0.2

  mm and an upper internal diameter D'2 of 14.6 mm.

  The upper shell 2 has a central hole 3 in its bottom wall 4.

  The hole 3 has a diameter of the order of 3.5 mm in the embodiment

indicative considered above.

  A varnishing 5 of the hole 3 is carried out on the internal face 6 and the external face 7

  of the bottom wall 4 of the upper shell 2.

  The varnishing 5 forms a ring with an outside diameter of the order of 7 mm

in the realization considered.

  The varnishing is also carried out on the field 8 of the hole 3.

  Similarly, the lower shell 1 has a hole 3 'central in its bottom wall 4', this hole 3 'having substantially the same diameter as the hole 3 and

  comprising a varnishing 5 'similar to varnishing 5.

  We now describe the process or manufacturing and assembly of the shells

upper and lower.

  We first cut a rectangular block 10 of sheets of material

  conductive such as annealed copper, for example.

  This cutting can be carried out with a band saw, by water jet, by laser, by

  EDM or any equivalent process.

  In this rectangular block 10, square packets 11 are cut, of

  dimensions 26mm X 26 mm X 5 mm, in the embodiment under consideration.

  Furthermore, squares 12, of dimensions 26 mm X 26 mm X 5mm, are cut from a second material such as aluminum, in the embodiment under consideration. The square packets 11 are pressed on a lathe between two squares 12 and the assembly is reduced in lathe until a washer, of diameter of

  of the order of 22 mm in the embodiment considered.

  The lower shell 1 is moreover shaped by pressing, stamping,

  forming or any other equivalent process.

  Likewise, the upper shell 2 is shaped by pressing, stamping,

  forming or any other equivalent process.

  The varnishings 5, 5 'are carried out on the two faces 6, 6', 7, 7 'of the bottom walls 4, 4' of the upper and lower shells, as well as on the fields 8, 8 '

holes 3, 3 '.

  The two shells are then placed on the winding and a wire 13 is welded to the upper shell, in the vicinity of its lower free edge, so that the

  solder electrically connects the two shells.

  The use of a transformer screen as described above made it possible to reduce the parasitic capacity and to protect the user (corresponding to the

  secondary) of a high dielectric voltage.

  Parasitic capacitances of the order of 1.7 pF and effective user protection for a dielectric voltage of the order of 300 VAC have been obtained for line transformers type 86F9691 and 86F9692 (IBM)

Claims (13)

  1. Electromagnetic protection element intended to be associated with a transformer, characterized in that it comprises, in combination: - a lower shell (1) provided with a through hole (3 ') on its bottom wall (4' ) an annular skirt projecting from said bottom wall (4 '); - an upper shell (2) provided with a through hole (3) on its bottom wall (4) an annular skirt projecting from said bottom wall (4); - the upper shell (2) being nestable, over part of the height of its annular skirt on the lower shell (1); - varnishings (5, 5 ') on each of the two faces (6, 6', 7, 7 ') of the bottom walls (4, 4') of the shells (1, 2) around the through holes (3, 3 '); - a wire (13) welded to the upper shell, in the vicinity of its free edge   lower, so that the weld electrically connects the two shells.   2. electromagnetic protection element according to claim 1, characterized in that the through holes (3, 3 ') are substantially of the same diameter and placed facing each other when the shells are nested.   3. electromagnetic protection element according to claim 1 or 2, characterized in that the shells (1, 2) are of symmetry of revolution around   of a central axis with respect to the through holes (3, 3 ').   4. Electromagnetic protection element according to any one of   Claims 1 to 3, characterized in that the shells (1, 2) are produced   in a material chosen from the group comprising copper, copper alloys. 5. Transformer provided with an electromagnetic protection element such as   defined in any one of claims 1 to 4, the winding being inserted between the shells (1, 2).   6. Method of manufacturing a protective element as defined in one   any one of claims 1 to 4, characterized in that it comprises the   stages of: - shaping by pressing, stamping, stamping of an upper shell; - shaping by pressing, stamping, stamping of a lower shell; from a strip of conductive material such as copper or a copper alloy. 7. Method according to claim 6, characterized in that it comprises a step of drilling the through holes (3, 3 ') after the forming of the shells (1, 2).   8. Method according to claim 6, characterized in that the through holes   (3, 3 ') are drilled before the shells (1, 2) are shaped.   9. Method according to claim 6, characterized in that the drilling and the   forming the shells (1, 2) are substantially simultaneous.   10. Method according to any one of claims 6 to 9, characterized in that   that it comprises the subsequent stages of varnishing on the field of the through holes and around said holes (3, 3 ') on each face of the bottom wall shells (1, 2).   11. Method according to claim 10, characterized in that the varnishing is   made on an annular sector around the through holes (3, 3 ').   12. Method according to claim 11, characterized in that the diameter of the annular sector is of the order of twice the diameter of the through holes (3, 3 '). bed   13. Method according to any one of claims 6 to 12, characterized in   what it includes a step of welding a wire on the upper shell, in the vicinity of its lower free edge, so as to electrically connect the two shells (1, 2).