FR2488438A1 - METHOD FOR MANUFACTURING A TRANSFORMER CORE OR THE LIKE FROM AN AMORPHOUS METAL STRIP - Google Patents

Abstract

ACCORDING TO THIS PROCEDURE, A CONTINUOUS STRIP OF AMORPHOUS METAL, NOT ANNUITATED, IS WOUND AROUND A CORE TO FORM AN INITIALLY ROUND CORE. THE LATTER IS THEN TIGHTENED IN A PREDETERMINED WAY AND CUT ENTIRELY IN A CROSS SECTION, APPLYING IT A LIQUID COOLANT INHIBITING OXIDATION. THE RESULTING BANDS, NOT CONNECTED BETWEEN THEM, ARE THEN SEPARATED INTO A CERTAIN NUMBER OF GROUPS THAT ARE ASSEMBLED TO FORM AN OVAL CORE. THIS CORE, IN ITS FINAL FORM, IS ANNUCED AND SUBMITTED SIMULTANEOUSLY TO A MAGNETIC FIELD OF A PREDETERMINED DENSITY.

Description

Process for manufacturing a transformer core

  or the like from an amorphous metal strip.

  The present invention relates in a way

  general to magnetic cores intended for trans-

  trainers or electrical apparatus similar to induc-

  tion, and relates more particularly to a process by-

  particular manufacture of a magnetic core from

of an amorphous metal strip.

  A common way to make a mag kernel

  netic for an electrical appliance such as a transformer

  mateur is to use a strip of mag-

  netic whose preferred direction of orientation is parallel to the longitudinal direction of the material, i.e. it is a metallic material not

  amorphous. This material is relatively flexible and fa-

  eyelash to put in final shape of the core, before or after its stress elimination annealing. Therefore,

  when the nucleus has been formed, it can easily receive

  an unassembled joint, for example by cutting it entirely along a circumferential section and,

  thanks to its flexibility, an electric winding

  can be easily mounted around a section,

  simply by opening the seal and inserting the

  bearing by this seal. Although this technique is entirely satisfactory when the core is made of a non-amorphous metal strip material, it does not

  was not satisfactory when the nucleus was

  read in an amorphous strip material. This is so because the strip material, for example METGLAS (brand name) manufactured by Allied Chemical Corp.,

  is a very thin, very brittle and very hard material.

  Many attempts to achieve a no-

  yau from this material in the usual way have not been successful, mainly because the strip of amorphous metal is difficult to shear without cracks forming along the shear line. In addition, even if this thin and brittle material could be sheared without cracking, the time required to produce assembled cores

  according to the current procedure so far would be increased

  due to the thinness of the material. It is nevertheless desirable to use an amorphous metal to form a core due to the reduction

  losses in the nucleus which it makes it possible to obtain.

  For these reasons, an essential object of the information

  vention is to offer an economical and rela-

  very uncomplicated to manufacture, from an amorphous metal strip of a magnetic core intended for a transformer or similar induction device

  electric, and more particularly, a method of using

  safe reading, as will be explained in more detail

  thereafter, the process described starts from a contiguous strip

  bare of an unannealed amorphous metal which is initially wound around a cylindrical mandrel to form a

  initially round core, which is then tightened

  predetermined and cut entirely in a sec-

  predetermined transverse tion. This operation of

  cutting, which requires the application of a coolant

  cooling inhibiting oxidation in the cutting section of the core, produces several metal strips

  elongated not interconnected. Unre-

  related are separated into a number of in-

  dividuals which are assembled, one group at a time, into a roughly oval shaped nucleus, which is then brought to the desired final shape if it does not already have this desired shape. Then the core is annealed and it is

  simultaneously subjected to a magnetic field of intense

predetermined site.

  The method according to the invention will now be

  described in more detail with reference to the figures on the

which:

  Figure 1 is a section through a magnet core.

  that assembled according to the invention, and Figures' 2a to 2e schematically illustrate

  a certain number of phases of the process described for realizing

  read the magnetic core of Figure 1.

  Among the figures, in which the elements

  similar elements are designated by the same reference numerals, FIG. 1 represents a magnetic core

  assembled according to the invention. This nucleus which is suitable for-

  especially for a transformer or other similar device with electrical induction, consists of a continuous strip of an amorphous metal, for example of a

  strip of METGLASR material mentioned above. The no-

  yau can be round, rectangular, almost rectangular, as shown in Figure 1 or it can have any suitable or desired shape. In the quasi-rectangular shape shown, the core has opposite branches 12 and 14, an upper bracket 16 and a lower bracket 18. One of these four sections, for example the upper bracket 16, has a joint 20 which serves to access inside and around the nucleus,

  to position one or more electric windings

  that associated. Figure 1 shows such a coil

ment in 22.

  The joint 20 can be a flat or direct bearing joint, it can be a step joint, it can

  be notched in a V, or have any other appropriate shape.

  In addition, the opposite end sections forming this joint can carry protective coatings such as those described in patent application of the United States of America Na 133 344 filed on March 24, 1980, in the name of Lin et al. Reference should be made to this patent application which also describes a method of assembling the associated winding (corresponding to

winding 22).

  FIGS. 2a and 2e illustrate a preferred method of producing a core 1, formed of one or more

  several continuous bands of amorphous metal, for example-

  ple the METGLASR material mentioned above. The figure

  2a shows two continuous bands 24. These bands are initiated

  tally stored on their own spools 26.

  The first phase of the present process consists in winding the strip or continuous strips around a cylindrical mandrel 28 to form an initially round core

  generally designated by 30. According to this process, it im--

  door that the core 30 is wound in a circle so that the

  movement of the strip or strips 24 is not sacca-

  die or other irregular movement which may cause

  ruptures. In addition, if the tapes are wound up

  turn of the mandrel 28 without excessive acceleration, the

  winding size can actually be increased.

  When an initially round core 30 has been

  formed it is clamped in the predetermined manner illus-

  shown in Figure 2b. The clamping device generally designated by the reference numeral 32 is shown schematically in this figure as comprising a base plate 14 of steel or other rigid material, and two removable clamping plates 36 of steel or other rigid material. Although not shown, a suitable device is provided for holding the clamping plates 36 above the base plate 34

  so that the initially round core 30 is main-

  held between them in a compressed state, practically oval as indicated by reference 38. In this regard, the

  opposite ends of the clamping plates 36 are

  placed together to leave a section exposed

transverse of the nucleus.

  When the oval core 38 is clamped in the position shown in Figure 2b, a cutting tool, preferably a power saw comprising an abrasive circular saw blade 40 made for example of aluminum oxide or silicon carbide with a binder of

  resin or rubber, is used to cut whole-

  the exposed cross-section mentioned above

  above from one edge of the oval nucleus to its opposite edge. For this purpose, the motor saw itself can be a table saw or a radial arm saw, and a suitable block 42, of steel or other rigid material, is preferably placed inside the core as shown Figure 2b, to receive the projecting edge towards the inside of the saw blade 40 and guide it

  along the nucleus as it cuts its cross section

  dirty exposed. At the same time, the block 42 serves as a support between the base plate 34 and the clamping plates 36 to allow greater compression of the sheets

  of the core on each side of the cross section

  sword. This reduces the possibility of cracks, burrs, and / or swelling along the cutting line. Anyway, when the cut is made, it results in several strips of elongated material not

interconnected-

  An amorphous metal is a non-crystal material-

  line. When the amorphous metal is overheated, the ca-

  superior magnetic characteristics of this material

  deteriorate (i.e. it loses its characteristics

  non-crystalline ticks). Therefore, an arrival of an oxidation inhibiting coolant is

  necessary to avoid overheating during cutting.

  The contact pressure between the material and the disc

  cut is critical. Heat is easily developed

  loppée under the effect of a high contact pressure.

  The contact pressure is controlled by the speed of

  disc rotation and workpiece feed speed.

  In a real embodiment, the tangential speed of the disc was 30.5 to 36.6 m / s and the speed of advance of the workpiece for cutting was 12.9 cm / h. This can, of course, vary depending on the cutting disc

  and cut material. The coolant in-

  hibant oxidation is provided continuously under the

  in the form of a spray, by means of a device

  property comprising for example two nozzles designated by 44 in FIG. 2b In a preferred embodiment, the coolant is a water-based agent, particularly water containing Nu oil from Pittsburgh Chemical Manifacturing Co., as an oxidation inhibitor. However, to further prevent oxidation, the different elongated, unconnected bands which result from the cutting operation described above are immersed in an alcohol-based product, particularly methyl alcohol to remove the most of the cooling water. The unbound strips are then heated in an oven, preferably at 125 C, for a sufficient period

  to dry them. Although the invention is not limited to

  water-based coolant, although it

  is preferred, and although the invention is not limited to

  ted to particular parameters used in the drying of the strips, when a coolant based

  of water is used, the drying phase mentioned above

  above is a very necessary phase in the process

  overall to avoid excessive oxidation and a profusion

  ment. The little oxide which is left on the unbound strips, under the effect of water, is so thin that it does not appreciably affect the volume factor between the turns of the finally formed core, but increases advantageously the surface resistance. After this treatment, the unbound strips can slide more easily on each other and do not stick together, so that they can be separated into groups and receive the appropriate end shapes

which will be described.

  As just noted, when the oval core28 has been cut and the resulting unbound bands have been dried (assuming that an agent

  water-based cooling was used), the ban-

  Individuals are assembled into a number of groups with ends of suitable shape, depending on the particular type of joint desired in the final product. FIG. 2c represents a group of unrelated strips, generally designated by 46. This group is represented with ends 46a and 46b in the form of a wedge, necessary to obtain the final joint of the form shown in FIG. 1. This particular configuration can be obtained by initially taking the entire stack of non-connected bands and aligning them

  squared at one end by pressing the ends

  tees with a flat block. If a greater slope is desired, the stacks can be offset by alternately tightening one end of the stack and the other,

  in synchronism with a bending of the pile. For some

  some types of seals, such as lap seals

  alternating support, this offset is unnecessary. Formerly

  except in the case of a square support joint or an inclined support joint, the stack is used in the individual groups 46 mentioned above. In all cases, if the ends of each group must receive coatings such as those described in the aforementioned patent application, these coatings must be provided for

this moment.

  When the individual groups 46 are formed, the outer group, i.e. the group of the longest unrelated bands, is fixedly held in an oval (preferably elliptical) shape

  with its ends brought together and used

  rees to stay in position, as shown in Figure 2d. As it appears, the external group 46 is maintained in the position described above by any suitable means, for example two clamping plates 48 facing each other. When the outdoor unit 46 is

  thus positioned, the other groups are placed success-

  repeatedly (one at a time) within the group ex-

  earlier, starting with the longest group of

  those that remain unrelated bands, and ultimately

  with the shortest group. This result is ob-

  held by flexing on itself each individual group

  dual so that it can be arranged concentrically

  inside the last group assembled. The group-

  pe thus assembled can then snap into posi-

  tion, so that its opposite ends are supported

  one on top of the other as illustrated in FIG. 2d.

  Although not shown, a suitable wire, tape or other device may be provided to avoid

  ter that the nucleus does not come out of its form.

  que) finally obtained between the clamping plates 48 when they are removed - The oval (or elliptical) core

is generally designated by 49.

  When the core 49 has been formed, if its oval or elliptical shape is not the desired final shape, it is brought into this latter shape. This is best achieved by using a series of pliers which can be easily. placed. For example, Fig. 2nd shows a series of internal and external clamping plates 50 which constitute a part of an overall clamping device, easy to carry out by any specialist. Although not shown, the entire apparatus includes a device intended

  to adjust the space between the different plates in re-

  gard and position of the plates relative to each other

  to others to obtain the desired shape of the nucleus.

  Figure 2e shows that the oval or elliptical shape of the core 48 of Fig. 2d is converted into an approximately rectangular shape as in FIG. 1. This quasi-rectangular shaped core, which is designated globally

  by reference numeral 53 carries an electric coil

  as generally designated by 54 which is wound around a section of the core 53 and which is connected to a source 56 of direct current or alternating current,

  which, passing through the coil, -develops a mag field-

  In one embodiment, the value of this field is from 400 to 1600 A / m (5 to 20 oersteds), preferably 800 A / m (10 oersteds). At the same time, the whole nucleus

  is annealed, preferably in a protected atmosphere

  trice, for example in a vacuum, in an inert gas such as argon, or in a reducing gas, for example a mixture of nitrogen and hydrogen. In a preferred embodiment, the core is annealed for one to three

  hours, preferably for two hours, at a temperature

  erasure of around 340 c at 3700C (the range of these temperatures

  peratures suitable for METGLASR 2605S and 2605SC from Allied Chemical Corp.). The core is cooled, preferably gradually, at a speed of 1.670C per minute to 1500C. How good

  known, losses in the nucleus are reduced when

  that it is annealed and subjected to a magnetic field. When the core 52 has been annealed and subjected to the magnetic field, the coil 54 can be removed and the final electrical winding or windings 22 can be placed around a section of the core, by any suitable means, preferably including that described in

the aforementioned patent application.

Claims (5)

  1 - Process for producing a trans-   former from an amorphous strip metal, process   characterized in that it essentially consists of   rolling at least one continuous strip (24) of amorphous metal around a cylindrical mandrel (28) to form a core (30) initially round, then to be tightened (34, 36)   set of cross sections of said initial core-   round on opposite sides of a cross section   predetermined soil, so that the latter is sufficiently exposed to cut it by means of a specific cutting tool (40), to completely cut said exposed cross section with said cutting tool   while simultaneously applying (44) a coolant   liquid oxidation inhibiting oxidation on said core and on said cutting tool in the exposed section, so as to form several elongated strips of said metal which are not interconnected, to release said cut core and to separate said unconnected strips into a certain   number of groups (46) formed at their opposite ends   seated in a predetermined manner, to assemble said groups into a core (49) of substantially oval shape   by first forming and maintaining the outer one of-   said groups (46) in said oval shape and then successively placing the other groups, one at a time, in the outer group so that the opposite ends of each group define a segment of a joint of specific shape in the cross section of said oval-shaped core, to form (50) said oval-shaped core in its final form (53) if it is not   already in this final form, and then anneal the-   says nucleus while simultaneously submitting it (54, 56)   to a magnetic field of a predetermined intensity.   2 - Method according to claim 1, character-   dried in that said coolant contains water, said unconnected strips being soaked in an alcohol solution and then being hot dried there   before being assembled to form said groups.   3 - Method according to claim 1 or 2, characterized in that the cutting operation is carried out with an abrasive disc (40) made of aluminum oxide or silicon carbide with a resin or rubber binder.   4 - Method according to any one of the res-   dications 1 to 3, characterized in that said core (53)   in its final form is annealed in a special atmosphere.   other than the ambient atmosphere for about 2 hours at a temperature between about 3400C and 3700C, while subjecting it to a magnetic field   from at least 400 A / m to around 1600 A / m.   - Method according to claim 4, character-   laughed in that said annealed core is initially re-   cooled from its maximum temperature to   about 150 "C at a speed of about 1.67oC / minutes (or 1050 / hour).   6 - Method according to any one of the claims   cations 1 to 5, characterized in that said cutting operation is controlled, said coolant being supplied so that the temperature of said   strip material resulting from said cutting operation   pe remains low enough for said material to be   band retains its amorphous, non-crystal characteristic line.