Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F41/00—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
  • H01F41/02—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets
  • H01F41/0206—Manufacturing of magnetic cores by mechanical means
  • H01F41/0213—Manufacturing of magnetic circuits made from strip(s) or ribbon(s)
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F27/00—Details of transformers or inductances, in general
  • H01F27/24—Magnetic cores
  • H01F27/25—Magnetic cores made from strips or ribbons

Definitions

• the present invention relates to wound transformer cores.
• Transformers cores are typically made of layers of magnetic steel in order to reduce eddy current effects.
• One approach has been to manufacture stacked cores in which Silicon Steel is cut into lengths and stacked on top of one another to form a stack of laminated steel.
• stacks are arranged in core configurations e.g., a figure 8 configuration in which the stacks are intertwined at their corners.
• This approach works adequately when dealing with Silicon Steel sheets that are typically of the order of 10 mil thick.
• the downside is two-fold. Firstly, the machinery for cutting and stacking the sheets is extremely expensive and due to the repetitive cutting actions and back and forth movements, is prone to frequent failure and requires a high degree of maintenance. Secondly, the flat stack technology becomes very time consuming and costly when using thinner material.
• An alternative method of making cores involves the winding of core material onto a reel.
• the transformer conductor is usually subsequently wound through the window using a bobbin to form coils on the core, or in some instances the ferromagnetic core material may be wound through the coil.
• the ferromagnetic material is cut to varying lengths (laminations) and wound into a generally square shape with gaps in the core that can be opened (unlaced) to allow coils to be landed upon the core at which point the core can be closed (re-laced) to complete the magnetic circuit.
• Extant techniques for manufacturing wound cores composed of amorphous metal are, for example, described in U.S, Pat. Nos. 5,285,565; 5,327,806; 5,063,654; 5,528,817; 5,329,270; and 5,155,899, which describe ribbon winding, lamination cutting, lamination stacking, lamination winding, annealing, and coating the edge of the core.
• the prior art wound cores typically have a generally rectangular shape with a joint at one end that can be opened (unlaced) to allow the landing of a coil that has been wound separately. Once the coil has been landed the core must be closed (re-laced).
• Irregularities in the laminations can prevent the joint overlaps from matching perfectly.
• the winding of the amorphous core into a generally rectangular shape can detrimentally impact the performance since stresses are introduced when forming the comers of the core.
• Amorphous laminations are thin, ranging from 0.001 to 0.001 1 inches in thickness.
• Amorphous metal also lacks the structural integrity of silicon steel, displaying instead the floppiness of wet tissue paper even though it has quite high tensile strength.
• silicon steel has much greater structural integrity than amorphous metal so that the silicon steel core is capable of retaining its shape once wound.
• Thin materials such as amorphous metal and nano-grain steel also require 5 to 10 times more layers to build up the core, requiring a longer winding process and more difficulties with unlacing and re-lacing of the core in order to land the coils on the core.
• Amorphous metal also becomes quite brittle once annealed, making this core manufacturing process quite complex when compared to the core manufactured from silicon steel. The brittleness of annealed amorphous metal leads to inevitable breakage and flaking when unlacing and re-lacing an amorphous core.
• a construction method for amorphous and nano-grain cores that eliminates lamination damage and breakage, reduces stress within the core, reduces the time to assemble the transformer, and the time required to wind the core would be very valuable. In particular, it would allow the realization of the potentially low losses offered by amorphous metal and nano-grain steel.
• the present invention relates to wound cores in which the core cross-section is arranged to approximate a circle.
• This has the advantage that the coils can be wound onto the legs of the core using a winding tube, while maintaining a good fill factor (ratio of core cross-sectional area passing through a coil relative to the total cross-sectional area offered by the coil for accommodating the coil) instead of having to open up the core in order to land the coils.
• This avoids breakages and gaps in the core material and thus reduces losses. It also eliminates the problems of flaking and damage to the core associated with unlacing and re-lacing.
• the method may include winding the core in a cruciform configuration as discussed in greater detail below.
• the present invention relates to single-phase gapless, wound cruciform transformer cores formed from wound, annealed, metal alloys, and to processes for producing these cores and for producing transformers using these cores .
• the wound metal alloy may comprise ribbons or strips of thin-strip metal.
• the thin-strip metal may be slit from master rolls of amorphous alloy or other thin-strip metal.
• the cores may comprise multiple wound rings of amorphous strips or other thin-strip metal without any cuts or gaps in the rings.
• cuts or gaps in a ring refer to discontinuities in a ring that are provided in order to land or place coils on a core. Inadvertent breakages in the strips, and the beginnings and ends of the continuous strips used in the winding of a core ring without the need for stacking sections of the strip are not considered cuts or gaps in the ring since they are not expressly cut in order to land a coil and do not provide gaps that extend all the way through the ring to allow the ring to be opened up for purposes of landing a coil.
• a single phase core in which the core comprises a wound ring-like structure that includes at least two rings wound on top of each other from different thin-strip metal strip widths. Each ring may be wound using multiple payouts of the same strip width to speed up the build.
• the rings may be formed in a race-track configuration with two substantially straight, parallel legs that are connected at each end by a yoke.
• the race-track configuration may be achieved by winding the rings onto a suitably shaped former, e.g. two half-circular sections spaced apart to define an oblong form or wound on a circular former and subsequently shaped into racetrack shape.
• racetrack includes a configuration in which the legs of the core are substantially straight and parallel and the yokes are either curved or are flat with rounded corners joining the yokes to the legs, i.e., a rectangular form with rounded corners.
• the core may be wound in a cruciform cross- section with at least one middle ring of a first strip width and an inner ring and an outer ring of a second strip width that is narrower than the first strip width.
• More than three rings with strips of different widths may be wound on top of one another in a stair step arrangement
• a single phase, wound transformer core comprising a ring-like structure that includes multiple rings of different widths arranged on top of each other to define a stepped cross-sectional ring-like structure.
• the terms “inner ring”, “middle rings” and “outer ring” will refer to the order in which the rings are wound on top of one another, first the inner ring, followed by one or more middle rings of different strip widths, followed by an outer ring.
• the number of layers per ring may be different for different rings.
• the rings may have a different height or build.
• the difference in width between adjacent rings may be constant or may vary.
• the inner and outer ring may have a smaller height or build than the one or more middle rings but the incremental change in strip width from one ring to the next may remain constant.
• the number of layers per ring may be the same for all of the rings but the change in strip width of the rings may be greater for the inner and outer rings than for the one or more middle rings.
• the determination of the widths and heights of the various rings can be calculated or arrived at graphically or empirically to achieve the best fill factor.
• either the strip width or the build (defined by the number of layers wound to form a ring) or both the strip width and the build may be chosen for each ring to optimize the fill factor (i.e., the amount of magnetic material in the circumscribed circle around the cross-section of the ring-like structure). It will be appreciated that if the ring-like structure is to be built from a pre-defined set of strip widths, the circumscribed circle will define the build or number of layers for each ring.
• the core is preferably thermally conditioned (annealed and domain set). This may involve heating the core to approximately 300°C.
• the core may be heated for a period of one to two hours, and in order to assist in domain setting the material a magnetic field may be established in the core, e.g., with a strength of approximately 20 Oerstedt, by passing DC current through a winding provided around the core leg or core yoke of the ring-like core structure, or by exerting a physical stress on the core material.
• a DC current-carrying winding a DC magnetic field is established in the core, which is maintained for one or two hours with the core at its elevated temperature of approximately 300°C.
• the surfaces of the wound core are preferably coated with an epoxy, such as Huntsman 5865 A & B, which is a two-part epoxy that cures at room temperature in other words an epoxy that is mixed with a curing agent, to define a shell that provides structural integrity to the wound layers of the core.
• an epoxy such as Huntsman 5865 A & B
• Different epoxies making use of different curing methods may be used to define the shell, for example, epoxy making use of a curing agent, ultra-violet light curable epoxy, etc.
• Layers of fiberglass material or fiberglass chop may be included in the shell .
• a method of making a transformer from a single phase core as defined above comprising winding transformer coils onto the core legs without cutting the core or otherwise opening up (unlacing) the ring-like structure.
• the winding typically includes using a machine designed to wind on the leg.
• at least one low voltage winding and at least one high voltage winding is wound onto the core.
• the low voltage winding may be wound onto one or both of two legs of the core by means of one or more winding tubes or using a bobbin using at least some of the steps set out below.
• the low voltage winding may include aramid insulation e.g.,DuPont NomexTMor an equivalent insulation. It may comprise a round or rectangular cross-sectional wire or one or more sections of foil that are wound onto the core leg by means of the winding tube. An insulating layer is then typically provided over the low voltage winding before winding the high voltage winding on top of the insulating layer. Cooling ducts may be included in either the low-voltage winding, the high- voltage winding, or both of the windings utilizing duct sticks or spacers. The number and size of the cooling ducts can be readily determined by calculation by anyone familiar with the art.
• a method of making a wound single phase amorphous core with substantially round cross-sectional legs comprising forming a ring-like structure by winding a first or inner set of multiple layers of amorphous metal of a pre-defined strip width, to define an inner ring of a pre-defined width and build, winding at least one middle set of multiple layers of amorphous metal on top of the first or inner ring to define at least one middle ring, the at least one middle ring being wider than the inner ring, and winding an outer set of multiple layers of amorphous metal on top of the at least one middle ring to define an outer ring, the outer ring being narrower than the middle ring.
• the width of the outer and inner rings may be the same.
• Multiple middle rings may be included in the core, the widths of the middle rings getting gradually wider until a maximum central ring width is reached, whereafter rings are wound that gradually get narrower again to define a cross-section that fits within a circumscribed circle.
• the ring-like structure may be formed to have a race-track configuration by winding the ferromagnetic core material onto a former that provides ring-like structure having a race-track shape.
• the former may include two spaced-apart semi-circular or other curved sections. Instead the rings may be wound onto a circular former to define a circular ring-like structure, which is thereafter deformed into a race-track configuration or rectangular configuration with rounded corners.
• the rings may be made of different grades of amorphous metal or other thin-strip metal. Within a ring some of the layers may be made of different grades of amorphous metal.
• a thin-strip metal core includes a core that is predominantly made of thin-strip metal, notwithstanding that one or more layers of strengthening material of a material other than thin-strip metal, e.g., silicon steel, may be included between rings or on the inside of the core or on the outside of the core.
• the structural integrity of the thin-strip metal ring-like structure may be enhanced by providing a shell around the core, e.g. ,by applying an epoxy to the outer surfaces of the core.
• the shell may include at least one of fiberglass material and noise-dampening material.
• the noise-dampening material may comprise beads, also referred to as phenolic balloons mixed into the resin that is applied to the core surfaces.
• the resultant core can then be used as part of a single phase transformer or can be combined with two similar cores to define a three-phase transformer.
• the method may instead comprise winding a single strip of magnetic steel that has been cut to define a strip with a double taper.
• the ends of the strip are tapered to be narrower than the middle of the strip.
• the strip defines two
• the strip may be cut using a laser, e.g., a continuous laser operating at a wavelength of 20nm.
• a transformer core wound from one or more tapered strips of magnetic steel material may include a single strip of double tapered magnetic steel material.
• double taper refers to the fact that both of the ends of the strip of magnetic steel material are tapered.
• single strip of magnetic steel material includes not only one but also two or more strips wound simultaneously one on top of the other as part of the formation of a single common ring.
• the double taper strip may define a first end and a second end, which are both narrower than the middle of the strip.
• both ends define a left and a right side to the strip
• typically the taper is applied equally to the left and right side at the first end of the strip and equally to the left and right side at the second end of the strip.
• the tapers may extend only along part of the length of the strip. Thus part of the strip (the central portion) may include parallel sides with only end portions of the strip being tapered.
• the tapers at the first or leading end and second or trailing end of the strip may be chosen so that winding the strip into a ring, e.g., a substantially rectangular ring with two substantially straight parallel leg sections and two connecting yokes provides a core cross-section for the first (or inner) half of the ring that is identical to the second (or outer) half of the ring.
• the tapered section may be longer and more gradual at the trailing end than at the leading end to take account of the increasing path length as the core is wound onto the former or mandrel.
• the tapers may be chosen so that the core defines an egg-shaped cross-sectional leg with a narrower part toward the outside and a wider part toward the inside since the majority of the magnetic flux will travel the shortest path i.e., along the inside of the racetrack.
• the resultant core ring will have a cross-section that is substantially rectangular with truncated corners, or may define a hexagonal or octagonal cross-section depending on the amount of taper and depending on whether the central portion of the strip includes a parallel-sided section. It will also be appreciated that instead of using one continuous strip tapering outward and then inward, a first outwardly tapering strip may be wound to define an inner ring, optionally followed by a parallel sided strip to define a middle ring, followed by an inwardly tapering strip to define an outer ring.
• the tapers along the left and right sides of the one or more strips strip may also be formed in a non-linear fashion to define curved left and right sides. It will be appreciated that the curvature of the left and right sides of the strip can be chosen so that when the one or more strips are wound the resultant core cross-section through a leg of the core will be circular thereby rninimizing the air gap between the core leg and a surrounding tube-wound coil.
• Figure 1 shows a front view of one embodiment of a wound transformer core of the invention
• Figure 2 shows a cross-sectional view through a leg of the core of Figure 1
• Figure 3 shows a cross-sectional view through a leg of another embodiment of a wound core of the disclosure
• Figure 4 shows a front view of one embodiment of a single phase transformer core of the invention showing the use of winding tubes to wind coils on the legs of the core,
• Figure 5 is a flow chart describing the winding process of the disclosure
• Figure 6 shows one embodiment of a single tapered strip of the disclosure
• Figure 7 shows another embodiment of a single tapered strip of the disclosure
• Figure 8 shows one embodiment of a double tapered strip of the disclosure (both first and second ends tapered the same way),
• Figure 9 shows another embodiment of a double tapered strip of the disclosure
• Figure 10 shows another embodiment of a double tapered strip of the disclosure
• Figure 1 1 shows a cross-sectional view through a leg of a wound core of the disclosure made using a strip such as that illustrated in Figure 8,
• Figure 12 shows a cross-sectional view through a leg of a wound core of the disclosure made using a strip such as that illustrated in Figure 9,
• Figure 13 shows cross-sectional view through a leg of a wound core of the disclosure made using a strip such as that illustrated in Figure 10,
• Figure 14 shows a yet another embodiment of a double tapered strip of the disclosure
• Figure 15 shows a cross-sectional view through a leg of a wound core of the disclosure made using a strip such as that illustrated in Figure 14,
• Figure 16 shows one embodiment of a core winder of the invention in which a laser cutter is mounted on the winder
• Figure 17 shows a strip slit to define two strips with tapered sides
• Figure 18 shows an exaggerated cross section through a ring formed from a straight sided strip with double taper starting with the narrow end of the strip
• Figure 19 shows an exaggerated cross section through a ring formed from a straight sided strip with double taper, starting with the wide end of the strip,
• Figure 20 shows a cross-section through another embodiment of a core leg of the present disclosure.
• Figure 21 shows a strip (not to scale) for forming a core as shown in Figure 20.
• the present invention provides a wound transformer core that is produced as a new ring-like wound core configuration that allows coils subsequently to be wound on the legs of the core without cutting the wound layers of the core.
• Figure 1 shows a top view of one embodiment of a wound transformer core 100 of the invention.
• the ring-like structure of the core 100 is made up of multiple rings 102 of magnetic steel, e.g., amorphous metal strip or nano-grain steel material or silicon steel, of different widths (not shown in Figure 1) wound on top of one another.
• the different widths of the rings 102 are best illustrated in the cross-sectional views of Figures 2 and 3.
• the ring-like structure defining the core 200 is made up of multiple rings, each of which is wound from one or more strips of magnetic steel.
• the different width rings define a cross-sectionally stepped structure within circumscribed circle 204 as shown in Figure 2.
• the first or inner ring 210 and last or outer ring 220 in this embodiment are made from one or more strips of a first width, which is narrower than the strips of the other rings.
• the second and second last rings 212, 222 are made from strips of a second width that is wider than the first width.
• a middle ring 230 is included between the second ring 212 and second last ring 222, the middle ring 230 being formed from strips of a third width that is wider than the second width, and has twice as many layers as either of the first or second rings.
• the widths of the rings are arranged to define a completed ring-like structure with a cross-section that has a stepped configuration but is substantially circular as depicted by the circle 204.
• the number of rings has been increased and the change in width from one ring to the next has been kept constant.
• the step height is reduced from one ring to the next as one moves from the middle ring 300 to the outer and inner rings.
• the build for the first and last rings 310, 350 is less than that for the second and second-to-last rings 312, 352, which in turn is less than the build for the third ring 314 and third-to-last ring 354, which is less than that of the fourth ring 316 and fourth-to-last ring 356.
• the number of layers per ring may vary from one ring to the next or remain constant.
• the change in ring width (as defined by the strip width) from one ring to the next may be a constant change or may become more pronounced toward the inner and outer rings.
• the circumscribed circle can be filled. Therefore by necessity, reducing the number of strip widths reduces the fill factor that can be achieved. Also, for a defined number of strip widths an optimum fill factor may be achieved if both the strip widths and the build may be selected. On the other hand, this optimum fill factor may not necessarily be achieved if the design of the core is limited to pre-defined strip widths based on strip widths available to the manufacturer in its inventory.
• the rings in the above embodiments were wound in a race-track configuration by winding onto an oblong former to define a core with two substantially straight, parallel legs joined at their ends by curved yokes.
• the rings were wound in a circular configuration and subsequently deformed to define two substantially parallel legs. Tests have, however, shown that greater winding speed is achieved and less stress is introduced into the core if the rings are initially wound in circular fashion to define a circular ring-like structure that is subsequently deformed to define two substantially straight, parallel legs joined at their ends by curved (e.g., semi-circular) yokes.
• split winding tubes can be placed around the legs and attached together for winding the primary and secondary transformer coils onto the legs without the need to cut the core in order to place or land the coils on the legs.
• FIG 4 shows in which two winding tube halves 400 are placed around each substantially straight core leg 410, 412 and connected together, e.g., by means of tape to define a winding tube 402 as shown around the leg 410.
• the two tube halves are secured to each other by means of a thermally graded tape wrapped around the tube 402.
• One or more gears or sprockets 420 that are split into two halves 422, 424 are secured to the winding tubes for purposes of rotating the tubes by means of a motor that engages the sprocket or gear with a chain or complementary gear.
• the sprocket or gear halves 422, 424 are provided with tabs 426 having threaded holes in them for receiving bolts to connect the sprocket or gear halves to each other.
• the gears engage the tube in a non-slip relationship, e.g., by providing the sprocket or gear with radially inwardly extending tabs for engaging complementary notches or holes in the tube.
• the present invention allows the coils to be wound on the leg. This avoids having to create gaps in the magnetic field path and avoids unlacing and re-lacing of core layers in order to land the coils on the core legs.
• the surfaces of the core are coated with an epoxy (step 502), which in this embodiment is a two-part epoxy (Huntsman 5865 A & B) that cures at room temperature.
• This has the benefit of strengthening the core.
• the epoxy also provides a smoother outer surface to the core, thereby making it easier for the winding tube to rotate on the core leg.
• the resin or epoxy coating is further strengthened by adding fiberglass chop into the resin or epoxy. Phenolic balloons are added to the resin to provide sound dampening as depicted by step 500. Once the epoxy has cured, the winding tube is rotatably attached to the core (step 504).
• an epoxy which in this embodiment is a two-part epoxy (Huntsman 5865 A & B) that cures at room temperature.
• This also provides a smoother outer surface to the core, thereby making it easier for the winding tube to rotate on the core leg.
• the resin or epoxy coating is further strengthened by adding fiberglass chop into the resin or epoxy. Phenolic balloon
• a low voltage winding is then wound (step 508), onto each of the legs.
• the windings may include a polymeric or other insulation e.g.,DuPont NomexTM .
• One or more layers of insulating material are then applied over the low voltage winding (step 514), before winding the high voltage winding on top of the low voltage winding.
• a low and high voltage winding can be applied to each leg or the high voltage winding can be wound on one leg and the low voltage winding on the other leg.
• spacers or ducts are included as part of the coil design process and are included into the windings for cooling purposes.
• spacers of the pre-designated thickness are axially arranged around the circumference of the winding between some or all of the winding layers (step 510). Spacers are provided in this embodiment between the low voltage and the high voltage windings (step 520).
• the process begins by winding discs with insulated rectangular wire (step 524).
• insulator for the wire DuPont NomexTM is used in one embodiment.
• a wire insulated with a polymer film that is compatible with the resins used between the layers of windings is used.
• Axially arranged duct spacers are again provided between the layers of the windings depending on the design requirements of the transformer (step 530).
• a thin coating of compatible polymer or a varnish is applied to the windings by spraying the polymer onto the windings using nozzles or by dipping the entire transformer in a polymer or varnish.
• the coils were implemented using aluminum or copper wire having a round cross section or a rectangular cross section and covered with Nomex.
• the invention could instead be implemented using foil material and insulators.
• foil conductors in the form of sheets could be wound onto the core legs using a winding tube.
• the foil is wound in two side-by-side sections that are then connected beginning to end so that the direction of the winding is the same for both sections (either both clockwise or both anti-clockwise).
• the invention is not limited to only one or two sections of foil. More than two sections can for instance be implemented. This also has the advantage that each section is narrower allowing resin to penetrate more easily between the coils.
• the core and resultant transformer whether used as a single phase transformer or used as a set of three single phase cores wired to define a three phase transformer, produces numerous advantages.
• the process produces an amorphous core with minimum stress in the core, which does not require multiple cuts or post annealing manipulation in order to land the coils.
• the simple ring-like configuration of each single phase core does not require physical interconnection of core material with other single phase cores and does not require cutting or splicing together of layers of core material, thereby allowing each core structure to be wound separately and very quickly.
• a core can be produced in much less time than any type of distributed-gap wound core.
• the configuration and process entirely eliminates damage to the core material due to cuts and gaps.
• Flaking and chips are virtually eliminated since there is no need to unlace the layers of core material in order to land the coils on the core, or to re-lace the core material.
• Testing has shown core losses using amorphous metal to be 6 - 10% lower than comparable Evans or five-legged amorphous cores.
• the cores produced may be operated at induction levels higher than amorphous Distributed Gap cores.
• the core can be operated at higher induction levels than three-phase configurations having different cross-sectional areas in parts of the core, such as Stadium cores provided by Haihong in China, and Hexaformer cores, both of which result in reduced core material in the yokes compared to the legs of the core.
• Audible sound levels have also been found to be lower at the higher induction levels than is the case with amorphous distributed gap cores.
• the single-phase transformers produced by this method are suitable for applications in which any other single-phase transformers are utilized, either as standalone single-phase transformers or wired together with other single-phase transformers to provide three-phase transformers.
• Cores using this invention may readily be produced ranging from 15 kVA through 3.3 MVA.
• the present application also includes the forming of a wound transformer core from one or more strips of magnetic steel material, wherein at least some of the strips have tapered sides.
• a single strip can be used having a first and a second end with a double-sided taper toward each end, which may or may not have a central un- tapered portion, as discussed in greater detail below.
• the taper may be cut with a laser.
• Haihong or Stadium
• the Haihong strip of magnetic core material 600 appears to be limited to a single taper along one side 602 that extends the full length of the strip of magnetic core material from a first end 610 to a second end 612 as illustrated in Figure 6. It will be appreciated that the depictions of the strip shapes given above and the other embodiments discussed below are not to scale. Actual strips will be significantly longer and the taper cut more gradually, and in many instances slightly curved.
• Figure 7 shows another embodiment of a single tapered strip 700 of the invention.
• the taper is applied to both the left side 702 and the right sides 704 of the strip and again extends along the entire length of the strip from the first end 710 to the second end 712.
• a second ring has to be wound on top of the first ring that tapers the opposite way, i.e. starts wide and ends narrow to define, for example a hexagonal cross-section.
• a central ring wound from parallel- sided strip material can be formed between the inner and outer rings to defined, for example, a core with an octagonal cross-section.
• Figure 8 shows one embodiment of a double tapered strip 800 of the present disclosure in which both the first end 810 and the second end 812 are narrowed relative to a central portion 830 of the strip.
• the strip 800 defines two opposite tapers.
• both the one side 802, e.g., the left side, and the other side 804, e.g., the right side of the strip are equally tapered and the tapers at the two ends do not extend all the way to the middle.
• the strip 800 defines a central portion 830 with parallel sides.
• Figure 9 shows another embodiment of a double tapered strip 900 of the invention that is similar to that of Figure 8. However in this embodiment the taper at the first end 910 and the taper at the second end 912 extend to the middle of the strip. As in the strip of Figure 8, the strip 900 is tapered identically along both the left and right sides, 902, 904.
• Figure 10 shows yet another embodiment of a double tapered strip 1000 of the present disclosure, in which the taper at the first end 1010 is different to the taper at the second end 1012.
• the tapers were depicted as straight-sided or linear tapers, for purposes of simplicity. In practice, however the taper will be curved in order to take account of the increasing path length as the ring's diameter increases. This will be discussed in greater detail below with reference to Figures 18-21.
• Figure 1 1 shows a simplified cross-sectional view through a leg of a wound core of the invention made using a strip similar to that illustrated in Figure 8 (but with the appropriate curvature to the taper). Since the central portion 830 of strip 800 is not tapered the resultant ring has a cross section that is substantially rectangular with truncated corners 1 100. By correctly choosing the curvature of the taper and length of each portion of the strip, an octagonal cross-section can be achieved.
• Figure 12 shows a cross-sectional view through a leg of a wound core of the invention made using a strip similar to that illustrated in Figure 9 (but with the appropriate curvature to the taper).
• the tapers at the two ends 910, 912 extended to the middle of the strip thereby defining a wound ring with a 6-sided cross- section, which may be arranged to be hexagonal if the curvature of the taper is calculated correctly.
• Figure 13 shows a cross-sectional view through a leg of a wound core of the invention made using a strip similar to that illustrated in Figure 10 (but with the appropriate curvature to the taper).
• the taper at the first end 1010 was different to that at the second end 1012, not only to take account of the greater path length toward the outer portion of the ring, but also to achieve a different cross-sectional profile to the core ring, resulting in a wound ring with a non-uniform or substantially egg-shaped cross-section.
• the tapers were depicted as linear tapers for purposes of simplicity, but for the purpose of achieving multi-sided cross-sections.
• the present disclosure also allows for non-linear tapers such as the strip 1400 shown in Figure 14, which provides a curved taper at both the left and right sides 1402, 1404 of the first end 1410 and the second end 1412 that is sufficient to achieve a cross-section with curved outer surface.
• non-linear tapers such as the strip 1400 shown in Figure 14, which provides a curved taper at both the left and right sides 1402, 1404 of the first end 1410 and the second end 1412 that is sufficient to achieve a cross-section with curved outer surface.
• the result is that when the strip 1400 is wound into a core ring the cross-section of the ring of this embodiment is substantially circular as shown in Figure 15, which shows a cross section of the resultant core ring formed from winding the strip of Figure 14.
• FIG 16 shows one embodiment of a core winder 1600 of the invention in which one or more laser cutters, e.g., a continuous 20nm wavelength laser, is mounted on the winder.
• two pay-out reels 1602, 1604 are used to wind two ribbons or strips 1630, 1632 onto a single former or winding head 1610, which in this embodiment is depicted as a race-track former 1610.
• the two ribbons or strips 1630, 1632 are wound simultaneously one on top of the other onto the same former 1610 to produce a single common race-track-shaped ring.
• only one of the pay-out reels 1602 or 1603 could be loaded onto the winder to wind only one strip onto the former 1610.
• the use of two strips wound simultaneously on top of one another onto a common former also referred to herein as a 2-ply or multi-ply arrangement, will be considered herein as forming a ring from a single or continuous strip or ribbon since multiple wound strips are wound simultaneously as one.
• the laser cutter in this 2-ply embodiment is implemented as 4 laser units 1620 for cutting both the left and right sides of each strip 1630, 1632 as the two strips are wound from the two pay-out reels onto the former 1610. In this embodiment the cut-off portions along the left and right sides of the strips 1630, 1632 are discarded or collected as scrap.
• the cut off portion can be wound onto one or two separate take-up reels.
• a strip 1700 such as that shown in Figure 17 could be slit diagonally as shown, to end up with two tapered sections 1702, 1704.
• the one strip 1702 can be wound onto a first take-up reel to form the inner ring of a core since it gradually increases in width.
• the second strip 1704 will be starting with the wide end and therefore define a gradually narrowing ring. This can subsequently be re-wound onto a new or third take-up reel to define a ring that is gradually increasing and thus usable as an inner ring for another core.
• One embodiment of the present disclosure involves forming a substantially square cross-sectional core with rounded corners, as shown in Figure 20, which can be achieved by trimming both sides of each end of the strip at a taper as shown in exaggerated fashion in Figure 21.
• the leading edge 2100 has the sides 2102, 2104 slit at a curve to define convex surfaces.
• the trailing edge 2106 has the sides 2102, 2104 tapered at a

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• Engineering & Computer Science (AREA)
• Power Engineering (AREA)
• Manufacturing & Machinery (AREA)
• Manufacturing Cores, Coils, And Magnets (AREA)
• Coils Of Transformers For General Uses (AREA)

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• 2012
  • 2012-10-18 EP EP12841237.6A patent/EP2769389A4/de not_active Withdrawn
  • 2012-10-18 BR BR112014009610A patent/BR112014009610A2/pt not_active Application Discontinuation
  • 2012-10-18 WO PCT/US2012/000520 patent/WO2013058808A2/en active Application Filing
  • 2012-10-18 CA CA2853037A patent/CA2853037A1/en not_active Abandoned
• 2014
  • 2014-04-25 ZA ZA2014/03037A patent/ZA201403037B/en unknown

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