MXPA00010085A - Energy efficient hybrid core - Google Patents

Abstract

A hybrid transformer core assembly having a first leg having a first end and a second end, a second leg having a first end and a second end, and opposing first and second yokes coupling the first and second legs to the first and second yokes to create a closed core. The first leg and second legs are made of a plurality of packets of laminations having a high grain orientation, and the first and second yokes are made of a plurality of packets of laminations having a lower grain orientation than the material of the first and second legs. Alternating laminations of the first and second legs are staggered to alternately extend beyond adjacent laminations of the respective leg at first and second ends thereof. a portion of the laminations of the first and second legs which extend beyond adjacent laminations of the first and second legs, respectively, overlaps portions of alternating laminations of the yokes and couples with notches of alternating laminations of the yokes. Additionally, a portion of the laminations of the first and second legs overlaps portions of alternating laminations of the yokes to similarly couples the legs with the yokes.

Description

HYBRID NUCLEUS EFFICIENT IN ENERGY Technical Field The present invention relates generally to transformers and, more particularly, to transformer cores and assemblies therefor. Background of the Invention Transformers are used extensively in electrical and electronic applications. Transformers are useful for scaling voltages up or down, for coupling signal energy from one stage to another, and for impedance equalization. Transformers are also useful for detecting current and energizing electronic trip units for circuit breakers such as circuit breakers and other electrical distribution devices. Generally, the transformer is used to transfer electrical energy from one circuit to another circuit using magnetic induction. A transformer includes two or more coils of multiple turns of wire placed in close proximity to cause a magnetic field of one coil to be linked to a magnetic field of the other coil. Most transformers have a primary winding and a secondary winding. By varying the number of laps contained in the primary winding with respect to the number of turns contained in the secondary winding, the voltage level of the transformer can be easily increased or reduced. The magnetic field generated by the current in the primary coil or in the primary coil can be largely concentrated by supplying a core of magnetic material on which the primary and secondary coils are wound. This increases the inductance of the primary and secondary coils so that a smaller number of turns can be used. A closed core that has a continuous magnetic path ensures that virtually the entire magnetic field established by the current in the primary coil is induced in the secondary coil. When an alternating voltage is applied to the primary winding, an alternating current flows, limited in value by the winding inductance. This magnetizing current produces an alternating magneto-motive force that creates an alternating magnetic flux. The flow is constricted within the magnetic core of the transformer and induces voltage in the linked secondary winding which, if connected to an electrical load, produces an alternating current. This secondary charge current then produces its own magneto-motive force and creates an additional alternating flow that is linked back to the primary winding. A charge current then flows in the primary winding of sufficient magnitude to balance the magneto-motor force produced by the secondary charge current. In this way, the primary winding carries both a magnetization current and a charging current, the secondary winding carries charge current, and the magnetic core carries only the flux produced by the magnetization current. Even when transformers generally operate with high efficiency, the magnetic devices always have losses in the sense that a certain fraction of the input energy will be converted into undesirable heat. The most obvious type of unwanted generation of heat is ohmic heating in the windings that results from the small, but inevitable resistance of the windings. Two other forms of loss occur in the nucleus itself, due to hysteresis losses and parasitic currents. The hysteresis loss represents the energy required to go around the hysteresis loop, taking into account the cyclical variation in time by alternately magnetizing and demagnetizing the nucleus. The parasitic current loss comes from the localized currents induced in the nucleus by a flux that varies with time which, in turn, causes ohmic heating. Eddy currents are currents induced in the magnetic core by the magnetic fields of the primary and secondary windings. If a solid core were used, it would act as a shortened turn that it encloses the flow path, thereby allowing the flow of a circulation current and producing a very high parasitic current loss. Consequently, to minimize the energy lost due to these parasitic currents, the magnetic core is formed by constructing it from thin laminations stamped with iron or steel foil. These laminations, for the most part, are isolated from each other by surface oxides and sometimes also by the application of varnish. The laminations reduce the magnitude of any circulating currents that flow, thus reducing parasitic current losses. Additionally, the steel used for laminations of the entire core, ie the legs and the yokes, is usually a silicon-iron alloy that has been cold reduced to increase the degree of grain orientation within the laminations and give a lower hysteresis loss due to the smaller area of the hysteresis loop.

Generally, after forming the laminated core, the primary and secondary coils are placed on the laminated legs. Unfortunately, standard transformer cores suffer from several disadvantages. Such disadvantages include inefficiency, large size, complex manufacturing and tooling requirements, and high cost. Additionally, the US Department of Energy has been conducting research to raise relative higher standards to the minimum efficiency requirements for transformers. Accordingly, a transformer core according to the present invention provides an inexpensive and simple solution to eliminate the disadvantages of the previous transformer cores. The transformer core of the present invention also responds to potentially stricter standards from the Department of Energy. SUMMARY OF THE INVENTION The transformer core of the present invention is adapted to be used in conjunction with primary and secondary coil windings to cause a magnetic field of one coil to bond to or cause a magnetic field in the other coil, and includes a first coil. leg, a second leg, a first yoke and a second yoke. The first and second legs have first and second ends and are coupled to the first and second yokes to provide a magnetic flux path. This magnetic flux path concentrates the magnetic field generated by the current in the primary coil, thus increasing the inductance of the primary and secondary coils. According to one aspect of the present invention, the first and second legs are made of a material having a high grain orientation, and the first and second yokes are made of a material having a lower grain orientation than the material of the first and second legs. The grain orientation of the material of the first and second legs is aligned in a direction substantially between its first end to its second end. This allows the legs to operate efficiently with high induction and a small cross-sectional area, such that the electric windings or coils can also be small, reducing costs and increasing the overall efficiency of the transformer. However, the yokes may be higher to reduce induction and loss of energy without impacting the size or performance of the legs and coils. According to another aspect of the present invention, the first and second legs and the first and second yokes comprise a plurality of lamination packages. In the preferred embodiment, the lamination packages of the first and second legs are placed in a stacked manner to alternately extend beyond adjacent lamination packages of the first and second legs, respectively, at the first end, the second end. , or at the alternating first and second ends. A portion of the laminations of the first and second legs extending beyond adjacent laminations of the first and second legs, respectively, at their first and second ends, overlap portions of the laminations of the first and second yokes to create a overlapping joint. This overlapping joint decreases the flow resistance magnetic and subsequently reduces the hum in the transformer. Additionally, the laminations for the legs and the yokes are substantially rectangular pieces that have straight cuts, providing easy machining capacity, little waste, and low cost. According to another aspect of the present invention, the hybrid transformer has a third leg between the first and second legs, the third leg being coupled similarly to the first and second yokes. As the first and second legs, the third leg comprises laminations of material having a high grain orientation. In addition, lamination packages of the third leg are stacked to alternately extend beyond adjacent laminations of the third leg at their first and second ends. According to yet another aspect of the present invention, primary and secondary windings are wound around the legs of the core. With the identified core, one, two and three phase transformers can be manufactured.

Other aspects and advantages of the invention will be apparent from the following description, taken in conjunction with the following drawings. Brief Description of the Drawings Figure 1 is a perspective view showing a transformer with a transformer core of the present invention; Y Figure 2 is a partial perspective view showing the transformer core of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Although this invention is susceptible of being embodied in many different forms, preferred embodiments of the invention are shown in the drawings and will be described herein in detail, with the understanding that this Disclosure should be considered as an exemplification of the principles of the invention and is not intended to limit the broad aspects of the invention to the illustrated embodiments. Referring now in detail to the drawings, and initially to figure 1, a three-phase transformer is shown which includes a laminated magnetic core 12 with three primary coils 14, 16, 18 and three secondary coils 20, 22, 24. The transformer 10 is manufactured in two stages: first the laminations of the magnetic core are constructed, and secondly They wind the primary and secondary coils around the legs of the core. Figure 2 illustrates a preferred embodiment of an energy efficient transformer core 12 constructed in accordance with the present invention. The transformer core 12 generally comprises at least two leg members, hereby a first leg member 28 and a second leg member 30, a first yoke 32 and a second yoke 34. In the form of preferred embodiment, the first leg 28 and the second leg 30 each comprise a plurality of packages 35. Each pack is formed by a plurality of laminations 35a. The laminations vary from 7 / 1,000"to 18 / 1,000". Each package is of the order of 1/4"thick Each package 35 of the first leg and each package 35 of the second leg has a first end 36 and a second end 38. The first end 36 of the first leg 28 and the first end 36 of second leg 30 are substantially adjacent to first yoke 32 for coupling the first and second legs 28, 30 to first yoke 32 as a magnetic flux path Similarly, second end 38 of first leg 28 and the second end 38 of the second leg 30 are adjacent to the second yoke 34 for coupling the first and second legs 28, 30 to the second yoke 34 as a magnetic flux path, In addition, each lamination 35a of the first leg and the second leg is made of a material having a high grain orientation Preferably, the leg laminations 35a are made of high grade oriented grain silicon steel.In the preferred embodiment, this steel is of the type that does not get old and it has a high magnetic permeability. Additionally, this steel is treated with a moisture resistant coating that prevents atmospheric corrosion. Magnetic steel of this type presents less reluctance to the magnetic flux in directions parallel to the favored magnetic direction than in the directions transverse to it. The grain orientation of the leg laminate material 35a, shown with an arrow in Figure 2, is aligned in a direction substantially between the first end 36 and the second end 38 (ie, along the longitudinal direction of each leg lamination). Similarly, the grain orientation of the laminations 35a, shown with an arrow in Figure 2, is aligned in a direction substantially from the first end 36 to the second end 38. Independently of the total number of legs of the core 12, each leg will have a grain orientation aligned substantially in the same orientation, ie from the first end 36 to the second end 38. Each of the packages 35 of the leg members is of substantially the same length, and has substantially straight cuts on each side and end of it. As shown in Figure 2, the laminations 35a of the leg members are preferably manufactured in the form of rectangles. Each leg lamination is perforated, cut or laser cut directly from adjacent laminations. With this configuration, unlike having angled or square end, waste is eliminated, thereby reducing the cost. Opposite first and second 32, 34 are adjacent to the first and second ends 36, 38 of the first and second legs 28, 30, respectively. Similar to the legs, the first and second yokes 32, 34 comprise a plurality of packages 35, each formed of a plurality of yoke laminations 35b. However, the material comprising the yoke laminations 35b has a lower grain orientation than the material of the leg laminations 35a. Preferably, the material comprising the yoke laminations 35b is non-oriented grain. Making the legs 28, 30 of top oriented grain material, coupled in an overlapped manner with yokes 32, 34 made of lower oriented grain material or unoriented grain, instead of having yokes made of top oriented grain material, contributes reduced losses in the boards. Specifically, with a hybrid core, the flow that is transferred from the leg to the yoke is not impeded by a direct transition from a high grain targeting element to another high grain targeting element positioned 90 'thereon. Additionally, all laminations of the legs and yokes have substantially straight edges and ends that provide a less expensive core. During the assembly of the overall transformer core 12, the plurality of leg laminations 35a, together with the plurality of yoke laminations 35b, is layered, one lamination layer over another, to form the respective packages. Figure 2 illustrates nine package layers. A core comprising twelve to twenty layers of packets has been found to work well, although it can easily be seen that various other packet numbers would suffice. The exact number of packages depends on the desired performance characteristics of the transformer core and the type of material being used. The packages 35 are stacked or placed such that alternating packets extend beyond adjacent packets at alternating first and second ends 36, 38 of the legs, respectively. More specifically, the packages of the first and second legs are stacked to alternately extend beyond vertically adjacent packages. Once the lamination layers are stacked, they are secured securely or otherwise by conventional means. The thickness of the magnetic core 12 depends on the number and thickness of the packages therein. The overlap is approximately from y * to W.

In the place where the laminations of the legs are joined with the laminations of the yokes, a magnetic coupling occurs. Specifically, the first and second legs 28, 30 are coupled to the first and second yokes 32, 34 to create a closed core 12. More specifically, as shown in Figure 2, the first end 36 of the first leg 28 and the first end 36 of the second leg 30 are adjacent the first yoke 32 for coupling the legs first and second 28, 30 to the first yoke 32, and the second end 38 of the first leg 28 and the second end 38 of the second leg 30 are adjacent the second yoke 34 for coupling the first and second legs 28, 30 to the second yoke 34 This magnetic coupling takes place in the overlap between the laminations of the leg and the laminations of the yokes, and between the stacked extensions of the laminations of the legs and the notches of the laminations of the yokes. With a core 12 having two legs 28, 30 and two yokes 32, 34, the closed core forms a continuous magnetic flux path from at least the first leg 28 to the first yoke 32, the first yoke 32 to the second leg 30. , the second leg 30 to the second yoke 34, and the second yoke 34 back to the first leg 28. The final result of the stacked legs provides an alternating overlap between the joints of the legs and the yokes, and an overall reduction in the joint losses. Specifically, in addition to the reduction in the potential resistance in the magnetic flux path when it is transferred from the high grain orientation legs 28, 30 to the low grain or non-grain orientation yokes 32, 34, the overlap between the yokes and the legs further reduces the resistance (reluctance) in the magnetic flux path. The overlap between the yokes and the legs also reduces the buzzing or magnetic noise associated with the transfer of flow from the legs to the yokes. A transformer assembly 10 having more than two legs, such as for a three-phase transformer, is constructed in a manner similar to that just described. As an example, with a third leg 50 as shown in Figure 1, the third leg 50 being between the first 28 and second 30 legs, the third leg 50 similarly comprises a plurality of packages having first 36 and second 38 ends. Each package is made of material having a high grain orientation that is aligned in one direction substantially between the first end 36 to the second end 38. Like the laminations of the first and second legs 28a, 30a, the packages of the third leg 50 are stacked to alternately extend beyond adjacent packets of the third leg at the first ends. and second 38. This scenario would be similar for any number of additional legs. The hybrid lamination process improves the magnetic permeability by ensuring that the grain direction of the material in the legs is the same as the magnetic flux path. Additionally, the hybrid lamination process ensures that the magnetic flux path is not impeded by a direct grain variance between the legs and the yokes. The transformer further includes a primary winding or primary winding 14, 16, 18, arranged around each leg member. A secondary winding or secondary coil 20, 22, 24 is also disposed around each leg member and is magnetically coupled with the primary winding so that the magnetic lines of force of the primary winding intersect with the secondary winding. Other arrangements of the primary winding and winding The secondary materials are suitable for use with the present invention. For example, the primary and secondary windings can be rolled side by side or have different degrees of overlap. Although specific embodiments have been illustrated and described, numerous modifications come to mind without significantly departing from the spirit of the invention, and the scope of the protection is limited only by the scope of the accompanying claims.

Claims (20)

1. CLAIMS 1. A transformer core, comprising: a first leg having a first end and a second end, the first leg being made of a material having a high grain orientation; a second leg having a first end and a second end, the second leg being made of a material having a high grain orientation; and first and second opposed yokes, made of a material having a lower grain orientation than the material of the first and second legs, the first and second yokes engaging the first and second legs to the first and second yokes to create a closed core .
2. 2. The transformer core of claim 1, wherein the grain orientation of the first and second legs is aligned in a direction substantially from the first end to the second end of each leg.
3. 3. The transformer core of claim 1, wherein the first and second yokes are made of a non-oriented grain material.
4. The transformer core of claim 1, wherein the closed core forms a continuous magnetic flux path extending from at least the first leg to the first yoke, the first yoke to the second leg, the second leg to the second yoke, and the second yoke back to the first leg.
5. 5. The transformer core of claim 1, wherein the first end of the first leg and the first end of the second leg are adjacent to the first yoke for coupling the first and second legs to the first yoke, and where the second end of the first leg and the second end of the second leg are adjacent to the second yoke for coupling the first and second legs to the second yoke.
6. The transformer core of claim 1, wherein the first and second legs and the first and second yokes are each made of a plurality of lamination packages, and wherein the packages of at least one of the first and second legs second are positioned to extend alternately beyond adjacent packets of the first and second legs, respectively, to one of the first and second ends.
7. The transformer core of claim 6, wherein the packages of the first leg are stacked to alternately extend beyond adjacent packets of the first leg at their alternating first and second ends.
8. 8. The transformer core of claim 6, wherein the packs of the second leg are stacked to alternately extend beyond adjacent packs of the second leg at their first and second alternating ends.
9. The transformer core of claim 6, wherein the packs of the first and second legs are stacked to extend beyond adjacent packs of the legs first and second, respectively, at their first and second alternating ends.
10. 10. The transformer core of claim 1, further comprising a primary winding around the first leg.
11. 11. The transformer core of claim 10, further comprising a secondary winding around the first leg.
12. 12. The transformer core of claim 1, further comprising a secondary winding around the second leg.
13. 13. The transformer core of claim 1, wherein the first and second legs are made of silicon steel with high grain orientation having a high magnetic permeability.
14. A transformer core assembly, comprising: a first leg comprising a plurality of laminations having first and second ends and made of a material of high grain orientation, where the grain orientation of the material of the laminations of the first leg is aligned in a direction substantially from its first end to its second end; a second leg comprising a plurality of laminations having first and second ends and made from a material of high grain orientation, where the grain orientation of the material of the laminations of the second leg is substantially aligned from its first end to its second end; and first and second opposed yokes comprising a plurality of laminations made of a material having a lower grain orientation than the material of the first and second legs, the first end of the first leg and the first end of the second leg being adjacent to the first yoke for coupling the first and second legs to the first yoke in a magnetic flux path manner, and the second end of the first leg and the second end of the second leg being adjacent to the second yoke for coupling the first and second legs to the second yoke in a magnetic flux path manner.
15. The transformer core of claim 14, wherein the grain orientations of the laminations of the first and second legs, respectively, are aligned in substantially the same orientation.
16. 16. The transformer core of the claim 14, wherein the laminations of the first and second legs are positioned to extend alternately beyond adjacent laminations of the first and second legs, respectively, at least at one of their first and second ends.
17. 17. The transformer core of the claim 14, where the laminations of the first leg are stacked to alternately extend beyond adjacent laminations of the first leg at their first and second alternating ends.
18. 18. The transformer core of claim 14, wherein the laminations of the second leg are stacked to alternately extend beyond adjacent laminations of the second leg at their first and second alternating ends.
19. 19. The transformer core of claim 14, wherein a portion of the laminations of the first and second legs that extend beyond adjacent laminations of the first and second legs, respectively, at their first and second ends, overlap portions of the laminations of the adjacent first and second yokes, respectively.
20. 20. The transformer core of claim 14, wherein the laminations of the first and second yokes are made of a material that is not grain oriented.