FR2789796A3 - Microwave oven voltage transformer construction having main C shaped section with inner piece tubular isolation piece ends folded and secondary/auxiliary winding having long side isolation unit. - Google Patents

Abstract

The high voltage transformer construction has an E shape section with a central column and a rectangular section with a secondary (4) and auxiliary winding (5). The central column of the E shaped section is covered with an isolating tube (11) with folded up sides. The folded sides protect the secondary winding. The secondary winding has isolating sections (8,9) along its sides.

Description

The present invention relates to the electrical insulation of

  high voltage transformers, in particular

  for a household microwave oven transformer.

PREVIOUS STATE

  High voltage transformers are known, for example for supplying microwave ovens, of the type which comprises an "EI" core with a central column of rectangular section, carrying in order a secondary high voltage winding. , such as 2,500 V, a winding

  auxiliary and a primary winding also with rec- section

  tangular; the long sides of the windings are wrapped in an individual insulation sheath made of a thin material, such as semi-rigid paper, in order to occupy less volume

  of the transformer. These long sides of the windings are

  castrated in the intervals between the columns of the nucleus; they are pressed against this central column and against the bottom of the intervals of the nucleus. During the mounting of the windings on the central column, the insulating sheath is subjected to friction against the sharp edges of the core, and risks being

  damaged. The different pieces of insulating paper made up

  the insulation sheath are connected together using an adhesive tape. To protect the tops of the secondary winding, and also to isolate it from the edges

  the core and bottom of these openings, a solution

  naked consists in surrounding the angles of the winding with a

  band-Aid. The forming of paper parts for the cons-

  truction of the sheath of the high-voltage secondary winding

  sion and their arrangement and connection on each side of the winding do not allow automated assembly of the

transformer.

  Document EP-294,297 discloses insulation for primary and secondary windings of a transformer

  for microwave ovens which, to facilitate self-mounting

  material windings, removes all adhesive tapes

  and avoids cutting and folding a multitude of iso-

  lantes. According to this solution, the winding of the windings is

  made on an insulating carcass with a flange at each ex-

  end to facilitate electrical connections, to which is connected a cover completing the insulating cover on all

the outline of the winding.

  Document US-5 440 286 describes a transformer

  of the known type, with insulating paper of tubular form

  turning a substantial length of the central column of the

  core, for insulation of interior surfaces of windings

  primary and secondary elements, and two insulating pieces with a "C" section for insulation of the external surfaces of

each winding.

STATEMENT OF THE INVENTION

  The object of the invention is an insulation for the secondary winding of a high voltage transformer

  as defined in the claims.

  The insulation according to the invention is fully

  rement carried out using insulating parts made from

  a strip of semi-rigid insulating paper, without adhesive tapes

  ves for insulation. The solution includes forming a reduced number of parts, two of them to isolate the outer surfaces of the winding and a central part

  tubular in shape to insulate surfaces and vertices

  tiors. This provides low cost insulation which

  complies with standards on separation safety distances, resists friction against the edges of the core and simplifies the operations of installing insulating sheaths on the

windings.

  The forming of the tubular central part solves

  the problem of folding semi-rigid insulation paper to

  hold the edges in a rectangular configuration.

  The insulation according to the invention also seeks coverage of the winding, in particular on the

  part in contact with the edges of the bottom of the core, without using

  read the edges of the tubular central part, which requires

  would be molded, rigid and expensive insulation. For this, the invention uses only a semi-rigid strip of paper as

main insulating material.

DESCRIPTION OF THE DRAWINGS

  - Figure 1 is an exploded perspective view of a trans-

  trainer according to the invention, - Figure 2 is a perspective view of the central insulating sheath of the transformer core of Figure 1, - Figure 3 is a bottom view of the transformer of Figure 1, showing the insulation secondary winding,

  - Figure 4 is a cross-sectional view along the line

gene IV-IV of figure 3.

  DETAILED DESCRIPTION OF THE INVENTION

  According to Figures 1 to 4, the transformer 1, provided

  insulation 8-12 according to the invention (fig. 1), including

  takes a ferromagnetic core 2 at "E", a primary winding

  mayor 3 of rectangular shape isolated from the core 2 and supplied with a voltage of 220 V at 50 Hz, a secondary winding 4

  rectangular in shape isolated from the nucleus, the tension of which

  tie is for example 2.500 V, an auxiliary winding 5

  mounted on the secondary winding 4, a flat core 6

  magnetic cation inserted between the primary winding 3 and the secondary 4, also electrically isolated; a cylinder head 2 'for closing the "I" core presses on the windings 3

  and 4 when it is connected to the core 2 at "E".

  The core 2 of the transformer has three columns 2a, 2b, 2a (Fig. 1); it is made of sheets stamped in "E" with

  right-angled sides and sharp edges.

  primary 3 and secondary 4 have a central trough 3 'and 4'

  respective, also rectangular, for their insertion

  tion during assembly of the transformer, around the co-

  central lonne 2b of the nucleus. The bundle of turns which constitutes each winding 3, 4 has a rectangular section and after its insertion into the core 2, the long sides 3a and 4a of the two windings (fig. 4) are embedded in the intervals 2c between the columns of the core and the sides 4a of the secondary winding against the bottom of the opening, the latter being subjected to friction with the sharp edges 7

of the nucleus 2.

  The windings 3 and 4 are coated beforehand with a sheath 8, 9, respectively, of electrical and semi-rigid insulating paper on the sides 3a, 4a of the respective winding and they are then inserted on the core 2. The sheaths insulating

  8, 9 are preferably made of an agglomeration of

  sine, formed by stamping from a strip of paper. In-

  Being the auxiliary winding 5 and the secondary winding 4, a sheet 10 of the same insulating paper maintains the mandatory safety separation distance between the windings. The two insulators 9 and 10 are connected to the winding 4 by a

  adhesive tape 12. The insulating sheaths 9 of the winding se-

  condaire 4 are separate for each side 4a and they have a "C" section which covers the three outer faces of each bundle of wires, leaving the face of the

central hollow 4 'of the winding.

  Insulation of the inside faces of the winding

  secondary 4 is carried out separately by a tubular sheath 11

  the same insulating paper (fig. 2), which surrounds the central column 2b of the core, up to the height occupied by the secondary winding 4 and the auxiliary winding 5 (fig. 4). The central sheath 11 has a contour adapted without play to the rectangular section of the central column 2b of the core, but it is open, and therefore its assembly is facilitated.

  on the central column (2b); its two ends lla ra-

  beat and completely close the rectangular section.

  When the winding 4 is placed on the central column 2b, it rubs against the central sheath 11 which very tightly surrounds the central column 2b. At its lower end, the central sheath 11 (FIG. 2) has a folded rim 11b which is inserted between the winding 4 and the bottom 2d of the openings 2c between columns. The winding 4 is thus also isolated from the sharp edges 7 of the openings 2c. The folded edge 11b and the sheath 9 of the long sides 4a are thus folded down (Fig. 3-4) to cover the entire outline of the package of turns. The central tubular sheath 11 is made from a semi-rigid paper strip by molding, including the folds of the rectangular outline and the fold of the rim 11b, as well as the

  plane deformation with curvature of the vertices llc of the rim 11b.

Claims (2)

R E V E N D I C A T I ON S   1) Electrical insulation for a high-voltage transformer   sion, of the type which includes a core (2) in "E" with a co-   central lonne (2b) with rectangular section, carrying in order at least one secondary winding (4), one winding   (5) auxiliary and a primary winding (3) with recirculated outline   also tangular, the central column (2b) of the core being covered with a tubular insulator (11) and the long sides (3a,   4a) windings are wrapped in a sheath (8,9) iso-   individual lante, and they are well-fitted   rée in the intervals (2c) between the columns (2a, 2b) of the core, characterized in that the tubular insulator (11) with rectangular contour is formed   a strip of semi-rigid insulating material, the ends of which   tees fold down until the outline is closed, and at one end it has a flange (11b) folded against the edges (7) of the bottom of the   intervals (2c) of the core, to isolate the winding (4) se-   condaire. 2) Electrical insulation of claim 1, characterized in that the tubular insulation (11) is formed in one piece, from a strip of paper agglomerated with resin, by molding and folding of this rim ( 11b) entirely around the four sides.