Patent Application
20150287513
1. Field of the Present Patent Disclosure
The present disclosure is generally directed to shaping or forming a portion of a transformer core (e.g., a leg or a yoke of a transformer core) wherein the core comprises a plurality of amorphous metal strips. In one arrangement, such a transformer core may comprise an annealed transformer core. For example, in such an annealed transformer core, the amorphous strips making up the core may be pre-annealed before core formation of the core, after core formation, or perhaps a combination of both. Specifically, the present disclosure is generally directed to methods and systems for shaping an electric transformer core comprising a plurality of metallic strip packets or groups, wherein each packet or group may comprise a plurality of thin amorphous metal strips. These thin strips of amorphous metal are arranged in a collection of packets or groups comprising multiple-strip lengths. These collections may then be arranged to surround steel plates to form a rectangular or square shape known as the core window. Thereafter, after the completed core has been formed, the amorphous core may be energized with a magnetic field while undergoing an annealing process. The annealing process results in a core which has magnetic properties which are highly desirable for use in electrical transformers. The annealed amorphous core then undergoes a testing procedure wherein certain known electrical properties of the now annealed core are tested. If the annealed core passes such tests, the core then undergoes a finishing step wherein the shape and dimensions of the core as defined by the steel plates, as well as the overall containment of the annealed amorphous material is secured. In one arrangement, the annealed core undergoes a finishing step wherein the shape and dimensions of the core as defined by a cap placed along at least a portion of a leg of the core. The cap may comprise an oil-compatible, paper-like material. Alternatively, the cap may comprise a layer of epoxy along at least a portion of a top surface or cast edge of a core leg. Alternatively, the cap may comprise an adhesive strip (e.g., a strip of tape) provided along at least a portion of a top surface or cast edge of a core leg. However, aspects of the present application may be equally applicable in other scenarios as well.
2. Description of Related Art
Electrical-power transformers are used extensively in various electrical and electronic applications. For example, as is generally known in the art, transformers transfer electric energy from one circuit to another circuit through magnetic induction. Transformers are also utilized to step electrical voltages up or down, to couple signal energy from one stage to another, and to match the impedances of interconnected electrical or electronic components. Transformers may also be used to sense current, and to power electronic trip units for circuit interrupters. Still further, transformers may also be employed in solenoid-equipped magnetic circuits, and in electric motors.
A typical transformer includes two or more multi-turned coils of wire commonly referred to as “phase windings.” The phase windings are placed in close proximity to one another so that the magnetic fields generated by each winding are coupled when the transformer is energized. Most transformers have a primary winding and a secondary winding. The output voltage of a transformer can be increased or decreased by varying the number of turns in the primary winding in relation to the number of turns in the secondary winding.
The magnetic field generated by the current passing through the primary winding is typically concentrated by winding the primary and secondary coils on a core of magnetic material. This arrangement increases the level of induction in the primary and secondary windings so that the windings can be formed from a smaller number of turns while still maintaining a given level of magnetic-flux. In addition, the use of a magnetic core having a continuous magnetic path helps to ensure that virtually all of the magnetic field established by the current in the primary winding is induced in the secondary winding. An alternating current flows through the primary winding when an alternating voltage is applied to the winding. The value of this current is limited by the level of induction in the winding.
The current produces an alternating magnetomotive force that, in turn, creates an alternating magnetic flux. The magnetic flux is constrained within the core of the transformer and induces a voltage across the secondary winding. This voltage produces an alternating current when the secondary winding is connected to an electrical load. The load current in the secondary winding produces its own magnetomotive force that, in turn, creates a further alternating flux that is magnetically coupled to the primary winding. A load current then flows in the primary winding. This current is of sufficient magnitude to balance the magnetomotive force produced by the secondary load current. Thus, the primary winding carries both magnetizing and load currents, the secondary winding carries a load current, and the core carries only the flux produced by the magnetizing current.
Certain modern transformers generally operate with a high degree of efficiency. Magnetic devices such as transformers, however, undergo certain losses because some portion of the input energy to the transformer is inevitably converted into unwanted losses such as heat. A most obvious type of unwanted heat generation is ohmic heating—heating that occurs in the phase windings due to the resistance of the windings.
Traditionally, electrical transformer cores have been formed completely of grain oriented silicon steel laminations. Over the years, improvements have been made in such grained oriented steels to permit reductions in transformer core sizes, manufacturing costs and the losses introduced into an electrical distribution system by the transformer core. As the cost of electrical energy continues to rise, reductions in core loss have become an increasingly important design consideration in all sizes of electrical transformers.
In order to further reduce these performance losses in transformers, amorphous metals having lower iron losses and higher permeability, have been used in forming electromagnetic devices, such as amorphous metal cores that can be used for electrical transformers. Generally, amorphous metals have been used because of their superior electrical characteristics relative to grain oriented silicon steel laminations. For this reason, amorphous ferromagnetic materials are being used more and more frequently as transformer base core materials in order to reduce undesired transformer core operating losses.
Generally, amorphous metals may be characterized by a virtual absence of a periodic repeating structure on the atomic level, i.e., the crystal lattice. The non-crystalline amorphous structure is produced by rapidly cooling a molten alloy of appropriate composition such as those described by Chen et al., in U.S. Pat. No. 3,856,513, herein incorporated by reference and to which the reader is directed for further information. Due to the rapid cooling rates, the alloy does not form in the crystalline state. Rather, the alloy assumes a metastable non-crystalline structure representative of the liquid phase from which the alloy was formed. Due to the absence of crystalline atomic structure, amorphous alloys are frequently referred in certain literature and elsewhere as “glassy” alloys.
Certain known methods and/or systems for manufacturing amorphous metal transformer cores are known. As just one example, U.S. Pat. No. 5,285,565 entitled “Method for Making a Transformer Core Comprising Amorphous Steel Strips Surrounding The Core Window” herein entirely incorporated by reference and to which the reader is directed for further reference, teaches such a method and system for making a transformer core wherein the transformer core comprises a plurality of groupings of amorphous metal strips. As described in U.S. Pat. No. 5,285,565, the disclosed method utilizes a plurality of spools of amorphous steel strip in each of which the strip is wound in a single-layer thickness. For example, and as illustrated in FIG. 1 of U.S. Pat. No. 5,285,565, a pre-spooler comprising five starting spools is illustrated. As the inventors describe in this patent, the strip from the five starting spools must first be unwound and then re-wound onto the pre-spooler. In this manner, the five single ply spools are unwound so as to create a five (5) ply ribbon or strip that then must be wound onto the pre-spooler.
One of the challenges faced by manufacturers of such amorphous transformer cores has to do with the nature of the amorphous metal strips themselves. For example, due to the nature of the manufacturing process, an amorphous ferromagnetic strip suitable for winding a distribution transformer core is extremely thin. For example, the thickness of a typical amorphous metallic strip may nominally be on the order of 0.23 mm versus a thickness of approximately 0.250 mm for typical grain oriented silicon steel. Moreover, such amorphous metallic strips are quite brittle and are therefore easily damaged or fractured during the processing, the annealing, and the handling of such strips. Consequently, the handling, processing, fabrication, annealing and shaping of wound amorphous metal cores presents certain unique manufacturing challenges of handling the very thin strips. This is particularly present throughout the various manufacturing steps of winding the core, cutting and rearranging the core laminations into a desired joint pattern, annealing and then shaping the core, and finally lacing the core through the window of a preformed transformer coil.
Of particular importance is the lacing step which must be effected with heightened care so as to avoid permanently deforming the core from its annealed configuration after the annealed core has past its electrical testing and after the annealed core has been inserted into the coil window. That is, if the annealed shape and orientation is not maintained, stresses may be introduced onto the amorphous metallic strips making up the core during the lacing procedure. Consequently, if there are significant stresses remaining after lacing, the low core loss characteristic offered by the amorphous metal core material is diminished. Since annealed amorphous metal laminations are quite weak and have little resiliency, they are readily disoriented during the lacing step, resulting in core performance degradation if not corrected. In addition to this concern, there is also a potential concern that the lacing step is carried out with sufficient care such as to avoid fracturing the brittle amorphous metal laminations.
The relatively thin ribbons of amorphous metals present certain core manufacturing challenges during the handing, processing, assembly and annealing of such amorphous metal transform cores. As just one example, certain amorphous metal transformer cores generally require a greater number of laminations or groupings or stacks of strips in order to form a desired amorphous metal core. As such, amorphous metal cores comprising a larger number of laminations tend to present certain difficulties and challenges in handling during the various processing steps that may be involved as the plurality of metallic strip groupings and collections are eventually processed, sheared, and then formed into an amorphous metal core.
In addition, the magnetic properties of the amorphous metals have been found to be deleteriously affected by mechanical stresses. Such mechanical stresses may be introduced during the fabricating and finishing steps of winding, forming, and final shaping (via epoxy or tape) the amorphous metal groupings and stacks into a desired core shape.
To facilitate the movement of the core through the various annealing, testing and epoxying process steps, a plurality of inner and outer core support plates are typically used in attempt to maintain the overall structure of the core while keeping both the outer walls and the inner walls of the core straight. For example, ordinarily a total of eight (8) support plates are typically provided so as to maintain the structural integrity and containment of the core during these further process steps. These support plates comprise four outer support plates and four inner support plates. In this example, two longer outer support plates are provided along the outer legs or side legs of the core. Similarly, two longer inner support plates are provided along the inner legs of the core. In a similar manner, two shorter outer support plates are provided at opposite ends of the core along the inner or side legs. In order to maintain these supporting plates in a supporting position, a metallic band is provided along an exterior of the supported core so that the plurality of support plates and hence the core are maintained or contained in a relatively fixed position. Essentially, these various support plates sandwich the core walls between the inner and outer plates and thereby provide a certain desired definition to the core walls. Importantly, the various support plates are typically used to sandwich the core walls; such that the plurality of amorphous metal strips and strip packets making up the inner and outer core walls are maintained in a uniform and straight fashion and the core walls are defined at a specific thickness, known as buildup.
For example, once an annealed amorphous transformer core has gone through an annealing process by being treated in a heated oven, the annealed core may then undergo certain testing to determine the operating characteristics of the annealed core. For example, an annealed core is typically tested to verify that the annealed core is below the maximum watts and maximum Volt Amperes (amps*test voltage=VA) at a specific induction level. If the annealed core does not pass certain test procedures, it could be due to a number of different causes such as a bad bus bar connection, an incorrect annealing temperature, improper length of time at the proper annealing temperature, etc. If the annealed amorphous core tests poorly due to inadequate time or temperature in the annealing oven, certain cores can be recovered by undergoing yet another annealing process.
Assuming that the annealed core passes its testing procedures, the various supporting plates must then be removed and the shape and dimensions of the annealed transformer core must then be secured so that the transformer core can then be packaged for transportation or assembled in a transformer. Importantly, the annealed transformer core must be transported and inserted into the coils without losing the shape and dimensions after undergoing the annealing process. As such, it is generally desired that prior to packaging and shipment, the shape of the annealed core must be secured so as to maintain its annealed (and therefore tested) shape.
Epoxy Shaping Method
Currently, after an amorphous core has been annealed, the core must be provided with a manner so that the core retains a certain degree of its annealed shape after the supporting plates are removed. One common method of provided such a shape support structure is by using one or more layers of epoxy provided along certain surfaces of the annealed core. In this method, the top and bottom surfaces of the core are covered with an epoxy with the exception of the overlap area which must remain opened and re-laced when the conductor coils are slipped on the core.
One generally known method for maintaining the annealed shape of the transformer core is to cover the majority of the top and bottom edges of the core walls with one or more layers of epoxy so as to provide structural strength and chip containment of the core. For example,
However, application of such an epoxy treatment presents certain disadvantages. For example, before the epoxy is applied, the overlap area of the core must be taped off so that the epoxy is administered properly along only certain outer surfaces of the annealed core. As just one example, one known method of epoxy treating annealed cores requires the following tedious and time consuming process steps:
The epoxy serves to contain any amorphous chips inside the core, and provide structure to the core and rigidity to the core legs, as the amorphous sheets of which the core is composed are quite flexible and will not readily hold shape of their own. As explained in greater detail, one disadvantage of applying one or more epoxy layers to the entire core leg and backwall is that this is a very costly process involving extensive labor as well as epoxy, tape, and disposable razor trimmer costs. Moreover, the epoxy provides no dimensional definition to the packets making up the core leg.
Another disadvantage of the above described epoxy process is that, at final buildup test when inner and outer plates are removed, if the core wall buildup is out of dimensional tolerance, then the whole core might need to be scrapped.
Another disadvantage of applying one or more epoxy layers to the entire core leg and backwall is that the various layers of the cured epoxy prevent the amorphous ribbon from moving in response to the magnetostrictive forces induced by the conductor coils. Amorphous materials become more resistant to magnetic flux when they are prohibited from moving in relation to magnetostriction.
Another disadvantage of the epoxy method is that often times, after a core has passed its electrical test after the annealing phase, the annealed core will fail its test after the epoxy has been applied. In certain instances, annealed core failures may occur because the one or more layers of the cured epoxy permanently deforms the annealed core from its annealed configuration as a result of shrinkage of the epoxy during curing, or inadequate maintenance of core shape and dimensions during the epoxy process. That is, if the annealed core is not returned to its annealed shape, stresses may be introduced after repeated epoxy application and curing procedures. Consequently, if there are significant stresses remaining after the application of the epoxy, the potential low core loss characteristic offered by the amorphous metal core material may not be achieved. A core with higher than acceptable losses must be scrapped.
Another disadvantage of the epoxy application method is that, after the final epoxy curing process step, the annealed cores must be manually trimmed so as to remove any excess epoxy along top and bottom of the annealed core. A certain degree of heightened care must be exercised during this epoxy removal step from the core inner and outer walls as failure to remove excess epoxy or a failure to properly remove any excess epoxy from this area may lead to scratches in the coil insulation and hence transformer failure. Of course, the excess tape and epoxy waste must be disposed of and therefore results in an environmental burden.
Tape Shaping Methods
In an attempt to overcome the various performance degradations that may be induced by this epoxy application method and its suspension of movement of the amorphous ribbon along with the laborious task of tape and excess epoxy removal process steps, a number of alternatives to this annealed core shaping process have been suggested. For example, one alternative to using epoxy is an attempt to provide annealed core support by loosely manually wrapping the core legs with lose or non-tensioned insulating paper in a spiral fashion like that of a candy cane, grip tape on a bicycle handlebar, or the grip on a baseball bat. In this manner, each successive wrap of the insulating paper would partially overlap the prior wrap. Typically, the wraps may be applied starting near the core overlap area, progress away from the annealed core overlap area along a first leg of the core, around the core, and then back near to the overlap area along the second leg of the core. Where the insulating paper begins and ends, it can be held in place with gummed tape. While this spiral taping method may serve to let the amorphous material move in response to the magnetostrictive forces induced by the conductor coils, it is a laborious method and consequently an expensive, time consuming process. In addition, for certain sized amorphous cores, it has been found that such a spiral taping method provides insufficient support of the legs of the transformer core thereby making the handing of such taped amorphous cores difficult, such as during handling or when inserting the core into the transformer coils.
Another disadvantage that might be experienced from such a spiral taping method is that, in order to gain core leg stability, the legs must be wound tightly. However, the cumulative pressure on the various stacks of the amorphous ribbon created by the paper restricts magnetostrictive motion, and can therefore (like the epoxy method mentioned above) significantly degrade overall core (and hence transformer) performance. Another disadvantage of such a taping method is that it is difficult to manipulate the annealed amorphous core so as to repeatedly wrap the tape around the complete core. For example, many times such amorphous cores may weigh upwards from approximately 1,000 pounds and therefore such typical amorphous transformer cores can only be moved and/or re-positioned along a work surface by operation of a large crane. As such, this increases the overall labor burden for using such a tape oriented core processing step. Moreover, taping of the core provides no dimensional definition to the packets making up the core leg.
Gummed Tape Shaping Method
Another alternative annealed core shaping method to using epoxy is to provide core rigidity and strength by wrapping the annealed core as described above, while using a gummed tape for the entire wrapping process around the length of the core, except for the core overlap area. In this manner, the gummed tape may be applied as a plurality of individual pieces, where each piece of tape may overlap one another or the tape may comprise a single continuous piece that wraps around the legs of the core and comes back to cover itself.
With such a gummed taping method, however, there are also a number of disadvantages. One disadvantage of such a gummed tape method is that application of the various taping is a very time-consuming process and has, therefore, further drawbacks. First, the tape application method is a slow and labor-intensive process. Second, the pressure exerted on the amorphous core from applying repeated tape applications tends to accumulate, as more and more tape is applied to the annealed transformer core. This cumulative effect causes an increase in pressure on the amorphous ribbon within the core and consequently results in an unwanted degradation in performance by preventing magnetostrictive motion of the annealed core. Third, the gummed tape is expensive. Fourth, the gummed tape, when applied in loose manner so as to attempt to minimize preventing the desired magnetostrictive motion, does not provide adequate support, structural containment, or dimensional definition for the core legs making handling and insertion of the core into the coils difficult. Fifth, there is no straight edge to reference the core leg against while applying the tape, making it very easy to shape the core leg in a crooked manner.
There is, therefore, a need for a more cost effective and less labor intensive method of shaping an annealed amorphous core in an environmentally friendly manner. Such a desired cost effective and less labor intensive core shaping method should also offer a certain desired degree of core rigidity and containment while also increasing manufacturing facility throughput. Such a cost effective and less labor intensive core shaping technique should also allow for maintaining the inner and outer core walls in a uniform and straight fashion, and particularly achieving such uniform and straight positioning of the amorphous core packets while also achieving a specified core buildup dimension. Achieving such uniform and straight dimensional definition of the amorphous core packets also allows for easier insertion of the annealed core into a transformer coil.
There is also a need for an annealed amorphous core shaping technique that provides adequate core support and amorphous chip containment while also allowing the amorphous core to achieve its desired magnetostrictive motion. There is also a general need for an annealed amorphous core shape definition technique that provides improved core support and containment while also reducing undesired transformer core operating losses while also reducing potential damage to the core that may result when removing excess epoxy.
These as well as other advantages of various aspects of the present disclosure will become apparent to those of ordinary skill in the art by reading the following detailed description, with appropriate reference to the accompanying drawings.
According to an exemplary embodiment, an annealed amorphous metallic transformer core comprising a plurality of amorphous metallic strip packets is disclosed. The plurality of amorphous metallic strip packets are assembled into a metallic transformer core, wherein the metallic transformer core comprises a back of the core, an overlap or front portion of the core, a first leg of the amorphous core extending from the back of the core to the front of the core, and a second leg of the amorphous core extending from the back of the core to the front of the core. A first cap is attached along at least a portion of the first leg of the amorphous core. The first cap may comprise an adhesive cap such as an adhesive strip. The cap providing rigidity and/or straight linear definition to the plurality of amorphous metallic strip packets contained within the leg of the amorphous core.
These as well as other advantages of various aspects of the present patent disclosure will become apparent to those of ordinary skill in the art by reading the following detailed description, with appropriate reference to the accompanying drawings.
Exemplary embodiments are described herein with reference to the drawings, in which:
a illustrates a joint located near an overlap or front portion of a core in an open state so as to permit a portion of the amorphous core so as to receive coils during a transformer assembly step;
b illustrates a method step of inserting a core into a coil window; and
c illustrates a method step of re-lacing a transformer joint after core insertion.
As is generally known in the art, an apparatus may be used to manufacture a plurality of groups or packets of amorphous metallic strips that can be further formed into a core and this core may then be used to fabricate an amorphous core transformer. As those of ordinary skill in the art recognize, transformer cores are fabricated from a plurality of grouping of stacks wherein each grouping comprises a plurality of amorphous metal strips. In one alternative preferred arrangement, transformer cores are fabricated from a plurality of groupings wherein one grouping may comprise a plurality of amorphous metal strips and wherein certain other groupings may comprise non-amorphous metal strips (e.g., grain oriented silicon steel). Still further, transformer cores may be fabricated wherein certain groupings may comprise both a plurality of amorphous strips along with non-amorphous metal strips.
Metallic Strip Packets
Specifically, and now referring first to
In addition, preferably, each group 16 (a-e) may comprise a plurality of thin layers of elongated metal strips. As just one example, each group 16 (a-e) comprises 15 (fifteen) thin layers of elongated strip. However, other group and strip arrangements may also be used. For example, group 16 (a-e) may comprise 15 thin layers of elongated strip wherein each one of the 15 layers is uncoiled from each respective uncoiler illustrated in
In each group, the layers of metallic strips have longitudinally-extending edges 18 at opposite sides thereof and transversely-extending edges 20 at opposite ends thereof. In each group 16a-e, the longitudinally-extending edges 18 of the strips at each side of the group are aligned. In addition, in each group 16a-e, the transversely-extending edges 20 of the strips at each end of the group are aligned. In the illustrated packets of
The increased length of these groupings of the metallic strips enables the groups 16 (a-e) to completely encircle the increasingly greater circumference of the transformer core form as the core form is built up on the winder section, that is, when the plurality of packets are wrapped about an arbor illustrated in
Referring still to
The core must be provided with a support fixture that provides core support and core containment during subsequent annealing and testing procedures. For example, referring now again to
Because of the flexibility of the amorphous metal strip packets, one or more support fixtures 64, 80 may be employed so as to maintain the overall integrity and shape of the annealed core 40. For example, in this illustrated support fixture arrangement, the first support fixture 64 comprises two long outer support plates 66, 68, two long inner support plates 72, 74, two narrow outer support plates 78, 80, and two narrow inner support plates 84, 86. Additionally, a second support fixture 90 in the form of a metallic band is provided along the outer circumference of the core and holds the various support plates of the first support fixture 64 in place.
As illustrated in phantom at 98, a joint 62 located near the overlap or front portion 50 of the core permits a portion of the amorphous core 40 (also referred to as the overlap of the core) to be opened so as to receive coils during a transformer assembly. As best illustrated schematically in
Once the core, such as the core and support structure illustrated in
In one preferred method of maintaining the annealed core in its desired annealed shape, one or more caps may applied over at least portion of at least one of the legs of the core. That is, in reference to the core illustrated in
As just one example,
As shown, the cap 100 comprises a generally rectangular shape and comprises a main body 102 extending along a length of the main body that is represented by Lmb 122. Preferably, the main body length Lmb 122 of the generally rectangular cap is generally equivalent to the length of one of the legs of the annealed core, such as the length of the first leg 54 of core 40.
As those of ordinary skill in the art will recognize, the cap 100 may comprise alternative lengths, sizes and/or shapes. As just one example, the cap 100 may comprise just a main body 102 without either a first longitudinal extending flap 106 or a second longitudinal extending flap 110.
As yet another example, the presently disclosed cap arrangements may be used with single phase or three phase (i.e., Evans style) transformers. For example, in a typical three phase transformer design, the transformer comprises basically two smaller cores of equal size diameter and cross-sectional area, together encircled by a larger core of equal cross-sectional area. In such a configuration, a single cap arrangement (such as the cap 100 illustrated in
As illustrated in
In one preferred arrangement, the cap 100 may be produced from an oil-compatible, paper-like material that will accept being folded so that the material maintains a sharp edge. In a preferred arrangement, the cap 100 comprises an insulation material, such as a Nomex® insulation material. Such an insulation material may preferably comprise a Nomex® paper having a thickness from approximately 0.005″ to approximately 0.050″.
The cap 100 may comprise a piece of material that covers the amorphous core along the cast edge of the amorphous material and attached to both the inside and outside of the core on either side of the cast edge. Further, the cap 100 may be attached to the cast edge using some type of adhesive or an adhering mechanism—such as tape, glue, epoxy, mechanical stitching, etc. or some combination thereof. In one preferred arrangement, the cap may be fixedly attached to the outer sides of the core legs and backwall using double sided tape. Such an adhesive prevents the cap material (and perhaps an over cap material as will be discussed with respect to
As such, the material wall is allowed to expand to maximum buildup (BU) dimension, which reduces stresses in the amorphous packets, resulting in better overall core and therefore transformer performance. This can also reduce or eliminate the need for inserting stuffing between the core wall and the end wall in the transformer. Since the overall core portion width is quite exact and repeatable, a slight interference fit can be designed for core and coil which therefore can eliminate the need for stuffers.
Another advantage of such a cap configuration is that the core will be more easily inserted into the coil. If packing is necessary to wedge between core leg and coil wall, it will now be easier to insert wedges as there will be no hanging up on uneven areas of the core wall that may sometimes arise if an epoxy layer is used. For example, taped core walls can be misshapen (i.e., they may be crooked or not straight) Forcing crooked or not straight legs into straight coils can induce stresses in the collection of amorphous ribbon thereby causing core performance losses.
Once the cap 100 is folded so as to form a crease between the main body 102 and the first and second longitudinal flaps 106, 110, the cap can be pushed onto a long edge of the core, and then affixed using a piece of tape. However, in one alternative arrangement, an epoxy, tape gum, double sided tape, combination thereof, or alternative adhesive may be applied to at least a portion of an underside of the cap before the cap is affixed to the annealed core. For example, as illustrated in
One important aspect of the cap 100 is the sharp bends or folded creases 114, 118 that define the first and second longitudinally extending flaps 106, 110. One advantage of such sharply defined bends is that they allow a core manufacturer to quickly and efficiently locate and line up the edge of the core leg and apply the cap 100 in a minimum of time in an exact location. This will allow the amorphous material in the core leg to experience the smallest amount of compression required to meet the maximum buildup specification.
Referring now to both
As illustrated in
One advantage of using cap 180 comprising a single flap is that is may be used with smaller core configurations and hence a smaller leg core width. In addition, in one cap configuration, two such L shaped caps may be used where a first alternative cap 180 is provided along the cast edge of the core with the flap 196 extending along the inner surface of the core leg. Similarly, a second such L shaped alternative cap 180 may be provided along the main body with the flap 196 extending along the outer surface of the core leg. In such an arrangement, the first cap 180 may comprise a piece of material that covers the amorphous core along the inner cast edge of the amorphous material and the second cap 180 may comprise a piece of material that covers the amorphous core along the outer cast edge of the amorphous material.
One advantage of using such a multiple cap arrangement is that it provides a limit to the amount of core wall expansion so that the maximum buildup stays within a desired specification. This may be accomplished without applying any unnecessary pressure when the core leg is straight—as it is when the core is installed in the transformer coil.
As those of ordinary skill in the art will recognize, alternative epoxy and adhesive methods may also be used to fixedly attach the cap to the leg of the transformer core.
After the epoxy and/or adhesive has been applied to the cap or multiple caps, the cap or multiple caps may then be affixed along a leg of the annealed core. For example,
One advantage of using such a cap 100 is that the first and second creases or bends 114, 118 allows a user to locate the caste edge of the core leg 54 and to apply the cap 100 in a minimum amount of time in an optimum location. Optimum cap placement along the leg cast edge allows the amorphous material of the core leg to experience the smallest amount of compression required to meet the maximum buildup specification.
Another advantage of the cap is that the cap provides a limit to the amount of core wall expansion so that the buildup stays within a certain desired specification, without applying any unnecessary pressure when the leg of the core is straight—as may occur when the core is installed in the transformer coil.
As also illustrated in
As can also be seen from
If it is determined that a greater cap rigidity is desired or specified for a particular size transformer core, then a thicker cap material can be applied. As just one example, the cap material may comprise an insulation material comprising a thickness from approximately 2 to approximately 30 mils. Additional rigidity may also be obtained by depositing a bead of epoxy along an inside of the cap before the cap is placed on the core leg as described above.
Yet another alternative core shaping arrangement may be used for more core stability. For example,
Specifically, and as shown in
In
Providing such an overlapping second cap arrangement 242 provides certain advantages. For example, one such advantage of such a dual cap configuration is that such a configuration (for certain sized annealed cores) may not require the use of tape for either the first cap or the second cap. Providing such a cap arrangement therefore results in labor savings as well as cost savings during the core shaping process.
Alternatively, if epoxy and/or adhesive were to be applied inside the first cap 244, the double cap can be placed on the core without the need for taping the cap to the core. If epoxy and/or adhesive were applied, the inwardly created pressure of the first and second cap flaps 252, 254 of the second cap 250 can be configured and dimensioned so as to hold the first and second caps in place until the epoxy cures.
Preferably, when a metal over-cap is used, the length of the paper cap flaps should be longer than the length of the metal cap flaps. For example, returning to
The following describes one preferred method for utilizing a plurality of caps to form and shape a metallic amorphous annealed core. For example,
At the second process Step 304, the annealed core 400 is placed on risers. Such a process Step 304 is illustrated in
Then, as illustrated in Step 306 in flow chart 300, the first and second outer support plates 366, 368 and the first and second inner support plates 372, 374 forming the various walls of the core are then raised in the direction away from the work surface. As just one example, these support plates may be raised approximately 1.0″ to about 2.0″ from their annealed position (as illustrated in
At Step 308, a first and a second cap 380a,b may be attached to a bottom surface of the first and the second legs 354, 358 of the core, respectively. The first and second caps 380a,b may be attached as described herein. For example, as illustrated in
Once the bottom first and second caps have been attached at Step 308, at Step 310, the outer band 374 holding the outer support plates in place can be cut and removed, thereby allowing the outside support plates to be removed. This step is illustrated in
Then, at Step 312, one wall at a time, an outer flap of the first top cap is located and attached to the outside of the each wall of the annealed core. For example, the outer flap of a first top cap is attached to the outside of the first wall and the outer flap of a second top cap is attached to the outside of the second wall. Thereafter, at Step 314, the first and second inner plates 372, 374 can then be removed by being pulled up, and removed from the window 342 of the core 400. Then, one at a time, at Step 316, the inner flaps of the first and second top caps can then be attached to an inside surface of each respective wall of the core.
As described herein in detail, an adhesive and/or an epoxy may be utilized to provide a heightened degree of stability to the cap arrangement utilized to shape a specific portion of the core. Returning to the method illustrated in
Accordingly, Applicants' presently proposed method and apparatus is directed to shaping or forming an amorphous metal transformer core that is cost effective to manufacture, that has low energy losses, that is energy efficient, and is more environmentally friendly than other known methods. Applicants' disclosed methods and apparatus is also directed to an amorphous metal transformer core in which the difficulties of handling, processing, and shaping the amorphous metal cores to perform the manipulative steps of the fabrication process are reduced and the mechanical stresses induced into the amorphous metal strips and hence the core during its fabrication process are reduced. As such, the disclosed methods and apparatus allows the amorphous ribbons to move in response to the magnetrostrictive forces induced by a transformer conductor coil and therefore increases overall transformer core performance. In addition, the presently disclosed systems and methods of shaping and forming of the amorphous metal core process is simplified since it does not require the labor intensive steps of taping, providing an epoxy, and repeated curing of the epoxy. As such, the presently disclosed methods and apparatus eliminates certain costly and labor intensive steps as discussed in greater detail above.
Exemplary embodiments of the present invention have been described. Those skilled in the art will understand, however, that changes and modifications may be made to these embodiments without departing from the true scope and spirit of the present invention, which is defined by the claims.
As just one example, the cap material may be selected from any suitable material for an amorphous metallic transformer core presently known in the art or later developed. Such materials may comprise a pliable material, an insulating material, a workable material and/or an adhesive material. For example, the cap material may comprise at least one of a thermoplastic material, a textile material, an insulation material, or an adhesive strip, such as a strip of tape.
As just one example, an alternative amorphous core cap may comprise a thermoplastic material, such as a thermo-softening plastic, or other similar polymer that becomes pliable or moldable above a specific temperature and returns to a solid state upon cooling. With such a thermoplastic cap arrangement, while keeping the forming support plates on the amorphous core during the capping process so as to maintain wall straightness and buildup, an epoxy or alternative adhesive may deposited on the cast edges where the thermoplastic material is to be placed. The areas with adhesive may then be covered with a strip of a thermoplastic material. In one preferred arrangement, the strip of thermoplastic material may be slightly wider than the wall buildup centered along the wall length, corners, and backwall. The amorphous core with the thermoplastic cap may then placed under a heating element in order to melt the thermoplastic material. In such a manner, the edges of the thermoplastic material will preferably overhang the core wall and bend over against the core wall. Once melted, the core may then be cooled. The core can then be flipped over and this thermoplastic capping process may be repeated on the other side core. The thermoplastic material may also be trimmed to the dimensions of a preferred buildup, if desired.
In yet another alternative cap arrangement, a cap may comprise a heavy textile material, such as canvas or other similar cloth or flexible woven material. Similar to the thermoplastic cap arrangement generally described above, while keeping the forming and support plates on the core so as to maintain wall straightness and buildup, an epoxy or an alternative adhesive may be placed on the cast edge of the core where the textile material is to be placed. Once the adhesive has cured, an overhang material may be attached to the core wall with adhesive, or trimmed away.
In yet another alternative cap arrangement, a cap may be formed using a heavy textile material as discussed above but in this arrangement, the textile may be attached to the core using adhesive only on a flap or flaps of the textile cap. The forming or support plates may be kept on the core during the capping process so as to maintain wall straightness and buildup as discussed herein.
In yet another example, a piece of tape, or other material through which epoxy or other bonding agent cannot pass, may be applied to a portion of the center core legs or backwall or both and epoxy or other bonding or fixative agent can be applied to the cast edge of core legs and backwall. Once the bonding agent has cured or hardened, the portion of the cast edge that was covered with the tape or other material will be allowed magnetostrictive motion. Such a core would then have limited performance degradation resulting from the shaping process and method.
As just one example, an alternative amorphous core cap may comprise an adhesive cap such as one comprising a strip of tape. In such a cap arrangement, one or more strips of an adhesive tape may be provided along various portions of the core, such as along at least a portion of one or more legs and/or the yoke. In one such adhesive cap arrangement, an epoxy may be applied in an “S” or complete or partial sinusoidal pattern(s) along one or more top surfaces of the core. The adhesive cap may then be applied over this core portion. The adhesive cap attaches to the silicon inner and outer wall of the leg, as generally described above with respect to cap 100 and
One advantage of such an adhesive cap is that such a cap helps to prevent amorphous chips from exiting the capped core. In addition, the epoxy underlying the adhesive cap provides increased core mechanical stability. With such an arrangement, once the underlying adhesive and/or the epoxy cures, since both the adhesive and the epoxy reside only on outside edges of the cast edge of the core leg, the core leg experiences a minimal amount of compression required to meet the maximum buildup specification while also allowing the amorphous core strips within the leg to achieve its desired magnetostrictive motion.
As just one example,
As those of ordinary skill in the art will recognize, the adhesive cap 600 may comprise alternative lengths, sizes and/or shapes. As just one example, the cap 600 may comprise just a main body 602 without either a first longitudinal extending flap 606 or a second longitudinal extending flap 610.
More preferably, a width of the main body represented by WMB 628 is designed to generally match a specified maximum buildup (BU) dimension for a transformer core leg. For example, the main body width WMB 628 may be designed to match the specified buildup (BU) 629 of the transformer core portion 630.
In one preferred arrangement, the adhesive cap 60 may be provided with a dimensional indicator near either one or both edges wherein a space or distance between these indicators corresponds generally to a core buildup (BU) dimension of the transformer core portion. For example, as illustrated in
The adhesive cap 600 may be applied by first applying one edge 606 of the cap 600 to the silicon inner sheet of the core portion, lining up the first dimensional indicator 614 with an edge of a silicon steel 632 of the core portion 630. Depending on the cap material selected, the cap 600 may then be stretched over, drawn across or pulled over the epoxied area of the core portion 630 and attached such that the second dimensional indicator 618 on the cap 600 aligns with an outer silicon steel edge 634 of the core portion 630.
After the adhesive cap has been applied over the epoxy, an operator can then smooth out the epoxy under the adhesive cap by hand, or through use of a roller, spatula, or by some other similar smoothing device. Thereafter, the partially capped core can then be flipped, and the core capping method may be repeated. (See, e.g.,
In one adhesive cap arrangement, the adhesive cap 600 may comprise reinforcement strands 650. As illustrated in
There are a number of advantages of using such an adhesive cap, such as cap 602.
For example, an adhesive cap can limit the maximum buildup size of an amorphous core leg and back wall. In addition, such an adhesive cap arrangement allows the individual amorphous ribbons making up the core portion to move independently of adjacent ribbons at the amorphous cast edge. As such, an adhesive cap restricts, but does not prevent parallel movement of amorphous ribbons from one another.
Moreover, an adhesive cap helps to maintain a maximum dimension for core leg and/or back wall buildup while an epoxy, glue, or other fixative material cures. After curing, portions of the adhesive cap, or in some applications the entire adhesive cap itself, may be removed. For increased core leg strength, the entire cast edge (core top/bottom) with exception of lacing area may be epoxied and tape or other material capable of maintaining buildup dimension placed on the core. This way, no curing process is required as the uncured epoxy is contained by the cap material. Neither edge masking nor edge trimming is necessary. This method will not take advantage of the performance gains resulting from allowing the amorphous sheets magnetostrictive motion.
An amorphous core having walls with intermittent application of epoxy applied to the cast ribbon edge so as to add structure stability to the core, while still allowing enough movement of the amorphous ribbon to allow magnetostrictive motion. The amount of epoxy applied will affect, though not necessarily linearly, the electrical performance of the core. Application of epoxy, glue, or other fixative agent, either completely or partially covering the back wall area to prevent compression of the amorphous sheets in the back wall area. Cap material should be flexible material but resistant to stretching.
As noted previously, the handling, processing, fabrication, annealing and shaping of wound amorphous metal cores presents certain unique manufacturing challenges of handling these thin metallic strips. This is particularly present throughout the various manufacturing steps of winding the core, cutting and rearranging the core laminations into a desired joint pattern, annealing and then shaping the core, and finally lacing the core through a window of a preformed transformer coil.
For example, as noted herein, one common transformer core manufacturing procedure is to wind the core independently of the transformer preformed coil and/or coils with which the cores will ultimately be linked. In such manufacturing procedure, the amorphous core is formed with a joint (such as the joint 62 illustrated in core 40 illustrated in
b illustrates a method of inserting the core 40 into a coil window. After insertion into the coil window, the opened up core can then closed to remake the joint.
As can be seen from
Exemplary embodiments of the present invention have been described. Those skilled in the art will understand, however, that changes and modifications may be made to these embodiments without departing from the true scope and spirit of the present invention, which is defined by the claims.
| Number | Date | Country | |
|---|---|---|---|
| 61954312 | Mar 2014 | US |
