Transformer including gaps

A transformer includes an outer peripheral iron core, and at least three iron core coils, which are in contact with or coupled to the inner surface of the outer peripheral iron core. The at least three iron core coils each include an iron core, and at least one of a primary coil and a secondary coil, which are wound around the iron core. Gaps, which can be magnetically coupled, are formed between two adjacent ones of the at least three iron cores, or between the at least three iron cores and a central iron core positioned at the center of the outer peripheral iron core.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a new U.S. patent application that claims benefit of Japanese Patent Application No. 2016-249312, filed Dec. 22, 2016, the disclosure of this application is being incorporated herein by reference in its entirety for all purposes.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a transformer including gaps.

2. Description of the Related Art

Conventional transformers include U-shaped or E-shaped iron cores having a plurality of legs, and coils wound around such iron cores. The coils are exposed to the outside of a transformer, and a magnetic flux leaking from the coil generates an eddy current at a metal portion in the vicinity of the coils. This causes a problem in which the metal portion of the transformer produces heat. In an oil-filled transformer, a transformer is contained in a metal storage container, and accordingly, it is necessary to prevent heat from occurring in the metal storage container due to the magnetic flux leaking from the coils.

In order to solve such a problem, in Japanese Examined Patent Publication (Kokoku) No. 5-52650, a shield plate is disposed around the coil, and, in Japanese Patent No. 5701120, a shield plate is bonded to the inside of a storage container. This prevents the metal portion in the vicinity of the coil or the storage container from generating heat.

In conventional three-phase transformers including E-shaped iron cores, the magnetic path length of a central phase is different from the magnetic path lengths of both end phases. Thus, it is necessary to adjust the balance of the three phases by differentiating the number of turns in the central phase from the number of turns in both end phases.

In this respect, Japanese Patent No. 4646327 and Japanese Unexamined Patent Publication (Kokai) No. 2013-42028 disclose a three-phase electromagnetic device provided with main windings wound around a plurality of radially arranged magnetic cores, and control windings wound around a magnetic core connecting the plurality of magnetic cores. In such a case, the balance of the three phases can be adjusted.

SUMMARY OF THE INVENTION

However, in Japanese Patent No. 4646327 and Japanese Unexamined Patent Publication (Kokai) No. 2013-42028, the control windings are located at the outermost portion of the electromagnetic device, and accordingly, the magnetic flux of the control windings may leak to the outside. Further, it is necessary to provide the control winding in addition to the main windings, and accordingly, the size of the electromagnetic device may be increased.

Further, in a converter transformer, a given number of legs, around which direct-current side windings and alternate-current side windings are wound, are comprised of iron cores with gaps. Thyristors are independently connected to the corresponding direct-current side windings. The alternate-current side windings are connected in series, and are connected to a power source. Such iron cores with gaps are used for a so-called series multiplex voltage source converter, and, regarding the responsiveness of their motion, the power source-side power factor, and the high-frequency wave, excellent properties can be obtained.

Regarding iron cores of a common transformer, the size of joint parts of cutoff plates of silicon steel sheets is reduced to reduce the magnetic resistance as well as the iron loss/exciting current and the oscillation noise. In contrast, regarding iron cores of a converter transformer, it is necessary to increase the magnetic resistance to a certain extent by forming gaps on the following two grounds.

(1) Slight gaps in the on-timing or discrepancies in control and differences in the impedance property of a circuit including a transformer in a thyristor generate a direct-current component current. When the DC current passes through the direct-current side winding, the direct-current biased magnetization occurs at an iron core, and then, the iron core is saturated. As a result, the exciting current increases, and the property of the device as a power conversion device is deteriorated, and additionally, the loss in the converter transformer increases, and the oscillation noise increases. It is difficult to completely prevent the occurrence of the direct-current biased magnetization. Thus, even if a DC current, which is approximately 1% of the rated current, passes, it is necessary to form appropriate gaps so as not to saturate the iron core.

(2) It is necessary to uniform the shared voltages of the alternate-current side windings connected in series, in order to maintain excellent motions of the device as a power conversion device. Thus, it is necessary to uniform the exciting impedance, i.e., the magnetic resistance between the phases in the converter transformer. If there are no gaps between the iron cores, variations in the magnetic property depending on the material of the iron cores, or non-uniform clearances between the joint parts of the cutoff plates make it difficult to make the magnetic resistance uniform. In contrast, if there are gaps between the iron cores, the variations in the exciting impedance can be reduced to several % or less by controlling the production of the device so that the lengths of the gaps are uniformed.

Further, the capacity of the transformer, which is necessary in a conventional power conversion device, is up to several tens of MVAs. Thus, even if the number of gaps per leg in the transformer is one, there is no problem because the thickness of each gap is merely several mm.

However, in a power conversion device in which the necessary capacity of the transformer is several hundreds of MVAs, the iron cores of the converter transformer are large, and accordingly, it is necessary to set the thickness of each gap at 10 mm or more. Consequently, the spread of the magnetic flux in a gap increases, and fringing magnetic flux components, which vertically enter an end face of the iron core, increase, and then, the local heating increases. Further, the magnetic energy accumulated in one gap increases, and the oscillation noise increases. Thus, it is very difficult to design/produce such a device as a real product. This is not economical.

The present invention was made in view of such circumstances and has an object to provide a transformer in which leakage of a magnetic flux to the circumference is prevented, and its size is not increased.

In order to achieve the above object, according to a first aspect of the invention, there is provided a transformer including an outer peripheral iron core, and at least three iron core coils, which are in contact with or coupled to the inner surface of the outer peripheral iron core. The at least three iron core coils each include an iron core, and at least one of a primary coil and a secondary coil, which are wound around the iron core. Gaps, which can be magnetically coupled, are formed between two adjacent ones of the at least three iron cores, or between the at least three iron cores and a central iron core positioned at the center of the outer peripheral iron core.

In the first aspect of the invention, the iron core coils each obtained by winding a winding around an iron core are disposed inside the outer peripheral iron core, and accordingly, the leakage flux from the winding to the circumference can be reduced. Further, providing a shield plate as in a conventional technology is not necessary, and a small transformer can be formed. Further, in a three-phase transformer, the magnetic path lengths of the three phases are structurally equal, and accordingly, the design and production can be easily performed. Furthermore, the ratio of the primary input voltage to the secondary output voltage is fixed, a control line is not necessary, and the size of the transformer can be further reduced.

These objects, features, and advantages of the present invention and other objects, features, and advantages will become further clearer from the detailed description of typical embodiments illustrated in the appended drawings.

DETAILED DESCRIPTION

Embodiments of the present invention will be described below with reference to the accompanying drawings. In the following figures, similar members are designated with the same reference numerals. These figures are properly modified in scale to assist the understanding thereof.

FIG. 1is a perspective view of a transformer based on a first embodiment of the present invention.FIG. 2Ais a sectional view of the transformer shown inFIG. 1. As shown inFIG. 1, a transformer5includes an outer peripheral iron core20having a hexagonal section, and at least three iron core coils31to33which are in contact with or coupled to the inner surface of the outer peripheral iron core20. Note that the outer peripheral iron core20may have a circular shape or another polygonal shape.

The iron core coils31to33respectively include iron cores41to43, and coils51to53wound around the iron cores41to43. Note that each of the coils51to53shown in, e.g.,FIG. 1andFIG. 2Acan include both a primary coil and a secondary coil. The primary coil and the secondary coil may be wound around the same iron core so as to lap over one another, or may be alternately wound around the same iron core. Alternatively, the primary coil and the secondary coil may be wound around separate iron cores. Note that the outer peripheral iron core20and the iron cores41to43are made by stacking a plurality of iron plates, carbon steel plates, magnetic steel plates, or amorphous plates, or are made of a magnetic body, such as a dust core or ferrite.

As is clear fromFIG. 2A, the iron cores41to43have the same dimensions, and are spaced at equal intervals in the circumferential direction of the outer peripheral iron core20. InFIG. 2A, the radially outside ends of the iron cores41to43are in contact with the outer peripheral iron core20.

Further, inFIG. 2Aetc., the radially inside ends of the iron cores41to43converge on the center of the outer peripheral iron core20, and the tip angle of each end is approximately 120 degrees. Further, the radially inside ends of iron cores41to44are spaced from one another via gaps101to104which can be magnetically coupled.

In other words, in the first embodiment, the radially inside end of the iron core41is spaced from the radially inside ends of the two adjacent iron cores42and44via the gaps101and104. The same is true for the other iron cores42to44. Note that it is ideal that the gaps101to104have the same dimensions, but it is acceptable that they have different dimensions. Further, in embodiments that will be described later, descriptions of, e.g., “gaps101to104” and “iron core coils31to34”, are omitted in some cases.

As seen above, in the first embodiment, the iron core coils31to33are disposed inside the outer peripheral iron core20. In other words, the iron core coils31to33are surrounded by the outer peripheral iron core20. Thus, the leakage of the magnetic flux from the coils51to53to the outside of the outer peripheral iron core20can be reduced. In other words, the amount of reduction in the leakage flux is larger than that in a conventional technology, and accordingly, the magnetic flux, which does not leak, passes through the iron core. Thus, the ratio of the mutual inductance to the self-inductance increases, and accordingly, a lower-loss and more efficient transformer can be realized.

Alternatively, the transformer5shown in, e.g.,FIG. 1can be used as a three-phase transformer. In this case, the magnetic path lengths of the three phases are structurally equal, and accordingly, the design and production can be easily performed. Further, the ratio of primary input voltage to secondary output voltage is fixed, and accordingly, conventional control windings are not necessary. Thus, an increase in the size of the electromagnetic device5can be avoided.

Further,FIG. 2Bis a sectional view of a transformer in a second embodiment. InFIG. 2B, the iron cores41to43are respectively comprised of tip side iron core portions41ato43aand base end side iron core portions41bto43b.

In this case, in a state where only the base end side iron core portions41bto43bare incorporated with the outer peripheral iron core20, the coils51to53are wound around the base end side iron core portions41bto43b. Subsequently, the tip side iron core portions41ato43aare inserted as illustrated.

It will be understood that this causes the coils51to53to be easily attached, and improves the assembling property. For this object, it is preferable that the coils51to53are not disposed in areas between the tip side iron core portions41ato43aand the base end side iron core portions41bto43b. Alternatively, each of the iron cores41to43may be formed from three or more iron core portions.

Note that it is preferable that the contact surfaces between the tip side iron core portions41ato43aand the base end side iron core portions41bto43b, and the contact surfaces between the base end side iron core portions41bto43band the outer peripheral iron core20are finished by mirror finishing, or have a fitting structure. This prevents gaps from being formed between the tip side iron core portions41ato43aand the base end side iron core portions41bto43band between the base end side iron core portions41bto43band the outer peripheral iron core20.

FIG. 3is a sectional view of a transformer based on a third embodiment of the present invention. The transformer5shown inFIG. 3includes an outer peripheral iron core20, and iron core coils31to36which are magnetically coupled to the outer peripheral iron core20and which are similar to the aforementioned iron core coils. The iron core coils31to36respectively include iron cores41to46and coils51to56wound around the iron cores.

The tip angle of the radially inside end of each of the iron cores41to46of the transformer5shown inFIG. 3is approximately 60 degrees. Further, the radially inside ends of the iron cores41to46are spaced from one another via gaps101to106which can be magnetically coupled. As seen above, the transformer5may include the iron core coils31to36, the number of which is a multiple of 3. In this case, the transformer5can be used as a three-phase transformer.

FIG. 4is a sectional view of a transformer based on a fourth embodiment of the present invention. As shown inFIG. 4, the transformer5includes an outer peripheral iron core20and four iron core coils31to34which are magnetically coupled to the outer peripheral iron core20. InFIG. 4, the iron core coils31to34are disposed inside the outer peripheral iron core20having an octagon shape. Note that the outer peripheral iron core20may have a circular shape or another polygonal shape. The iron core coils31to34are spaced at equal intervals in the circumferential direction of the transformer5. Not that it is only required that the iron core coils are arranged in the circumferential direction, and they do not have to be spaced at equal intervals.

As can be seen fromFIG. 4, the iron core coils31to34respectively include iron cores41to44, and coils51to54wound around the iron cores. The radially outside ends of the iron cores41to44are in contact with the outer peripheral iron core20, or are integral with the outer peripheral iron core20.

Further, the radially inside ends of the iron cores41to44are positioned in the vicinity of the center of the outer peripheral iron core20. In, for example,FIG. 4, the radially inside ends of the iron cores41to44converge on the center of the outer peripheral iron core20, and the tip angle of each end is approximately 90 degrees. Note that, as each tip angle decreases from 90 degrees, the area of each gap increases, but the magnetic flux saturation is easily caused by less current. Further, the radially inside ends of the iron cores41to44are spaced from one another via gaps101to104which can be magnetically coupled.

In other words, in the fourth embodiment, the radially inside end of the iron core41is spaced from the radially inside ends of the two adjacent iron cores42and44via the gaps101and104. The same is true for the other iron cores42to44. Note that it is ideal that the gaps101to104have the same dimensions, but it is acceptable that they have different dimensions. Further, in embodiments that will be described later, descriptions of, e.g., “gaps101to104” and “iron core coils31to34”, are omitted in some cases.

Thus, as shown inFIG. 4, a single X-shaped gap comprised of the gaps101to104is formed at the center of the transformer5. The gaps101to104are spaced at equal intervals in the circumferential direction of the transformer5.

As seen above, in the fourth embodiment, a central iron core, which is positioned at the center of the transformer5, is not necessary, and accordingly, the transformer5, which has a light weight and a simple structure, can be obtained. Further, the four iron core coils31to34are surrounded by the outer peripheral iron core20, and accordingly, magnetic fields, which have occurred from the coils51to54, do not leak to the outside of the outer peripheral iron core20. Further, the gaps101to104having a given thickness can be provided at a low cost. Thus, this transformer is advantageous in design to a transformer having a conventional configuration.

Alternatively, the transformer5may include iron core coils, the number of which is an even number not less than 4. In this case, it will be understood that the transformer5can be used as a single-phase transformer. Further, connecting coils in series or in parallel enables the output voltage or the rated current to be adjusted.

FIG. 5is a sectional view of a transformer based on a fifth embodiment of the present invention. The iron cores41to44extending in the radial directions of the iron core coils31to34in the transformer5shown inFIG. 5respectively include first iron core portions41ato44alocated at radially inside positions, third iron core portions41cto44clocated at radially outside positions, and second iron core portions41bto44blocated between the first iron core portions41ato44aand the third iron core portions41cto44c.

First iron core portion gaps111ato114a, which can be magnetically coupled, are formed between the first iron core portions41ato44aand the second iron core portions41bto44b. Likewise, second iron core portion gaps111bto114b, which can be magnetically coupled, are formed between the second iron core portions41bto44band the third iron core portions41cto44c. Further, the transformer5includes coils51to54wound around both the second iron core portions41bto43band the third iron core portions41cto44c. Note that the coils51to54may also be wound around the first iron core portions41ato44a.

In such a case, a gap, which is originally only the gap101, for one iron core, e.g., the iron core41is divided into the gap101, the first iron core portion gap111a, and the second iron core portion gap111b, and accordingly, the thickness of each gap reduces. The thickness of each gap in this case means a thickness of the gap101obtained by dividing the original gap, a distance between the first iron core portion41aand the second iron core portion41b, and a distance between the second iron core portion41band the third iron core portion41c.

FIG. 6is a sectional view of a transformer based on a sixth embodiment of the present invention. The iron core coils31to34of the transformer5shown inFIG. 6include iron cores41to44which radially extend, and coils51to54wound around the iron cores. The radially inside ends of the iron cores41to44are, as in the aforementioned embodiments, adjacent to one another via gaps101to104.

In the sixth embodiment, outer peripheral iron core gaps111cto114c, which can be magnetically coupled, are respectively formed between the radially outside ends of the iron cores41to44and the outer peripheral iron core20. When the transformer5operates, heat occurs at the iron core coils31to34. In the sixth embodiment, the outer peripheral iron core gaps111cto114care formed, and accordingly, the heat occurring from the iron core coils31to34is difficult to transfer to the outer peripheral iron core20.

FIG. 7is a sectional view of a transformer based on a seventh embodiment of the present invention. The iron core coils31to34of the transformer5shown inFIG. 7are substantially similar to the iron core coils which have been described with reference toFIG. 1. In the seventh embodiment, the outer peripheral iron core20is comprised of a plurality of, e.g., four outer peripheral iron core portions21to24. InFIG. 7, the outer peripheral iron core portion21is in contact with or integral with the iron core41. Likewise, the outer peripheral iron core portions22to24are respectively in contact with or integral with the iron cores42to44. In the embodiment shown inFIG. 7, even if the outer peripheral iron core20is large, such an outer peripheral iron core20can be easily produced.

FIG. 8is a sectional view of a transformer based on an eighth embodiment of the present invention. In the eighth embodiment, an outer peripheral iron core portion gap61, which can be magnetically coupled, is formed between the outer peripheral iron core portion21and the outer peripheral iron core portion22. Likewise, outer peripheral iron core portion gaps62to64, which can be magnetically coupled, are respectively formed between the outer peripheral iron core portion22and the outer peripheral iron core portion23, between the outer peripheral iron core portion23and the outer peripheral iron core portion24, and between the outer peripheral iron core portion24and the outer peripheral iron core portion21.

In other words, the outer peripheral iron core portions21to24are respectively disposed via the outer peripheral iron core portion gaps61to64. In such a case, the outer peripheral iron core portion gaps61to64can be adjusted by adjusting the lengths of the outer peripheral iron core portions21to24. Consequently, it will be understood that the unbalance of the inductance of the transformer5can be adjusted.

The transformer5shown inFIG. 8differs from the transformer5shown inFIG. 7only in that it has outer peripheral iron core portion gaps61to64. In other words, in this embodiment, the outer peripheral iron core portion gaps61to64are not formed between adjacent ones of the outer peripheral iron core portions21to24. In the embodiments shown inFIG. 7andFIG. 8, even if the outer peripheral iron core20is large, such an outer peripheral iron core20can be easily produced.

FIG. 9is a sectional view of a transformer based on a ninth embodiment of the present invention. The transformer5shown inFIG. 9is substantially similar to the transformer5which has been described with reference toFIG. 4, and accordingly, the explanation thereof is omitted. As shown inFIG. 9, a resin gap material71is charged into gaps101to104of the transformer5.

In this case, the gap material71can be made by simply charging resin into the gaps101to104and curing the same. Thus, the gap material71can be easily made. Note that the gap material71may previously be made as a substantially X-shaped gap material similar to that shown inFIG. 9, or an L-shaped or plate-like gap material, in order to insert the previously made gap material to the gaps101to104in place of charging resin. In such a case, the gap material71reduces the oscillation of the iron cores being in contact with the gaps101to104, and accordingly, can reduce noises occurring from the iron cores. Likewise, gap materials can be easily made by charging resin into the iron core portion gaps shown inFIG. 5and the outer peripheral iron core gaps shown inFIG. 8, and accordingly, it will be obvious that similar effects can be obtained in these gaps.

FIG. 10is a sectional view of a transformer based on a tenth embodiment of the present invention. The transformer5shown inFIG. 10is substantially similar to the transformer5which has been described with reference toFIG. 4, and accordingly, the explanation thereof is omitted. As shown inFIG. 10, the inside of the outer peripheral iron core20of the transformer5is filled with a resin insulating material72.

In this case, the insulating material72can be easily made by simply charging resin into the inside of the outer peripheral iron core20and curing the same. In such a case, the insulating material72can reduce the occurrence of noises by reducing the oscillation of the iron core coils31to34or the outer peripheral iron core20. Further, in the embodiment shown inFIG. 10, the insulating material can also promote temperature equilibration between the iron core coils31to34and the outer peripheral iron core20.

FIG. 11is a view of a machine or device including the transformer of the present invention. InFIG. 11, the transformer5is used in a motor driving device. Such a motor driving device is included in a machine or device.

As can be seen fromFIG. 11, the transformer5may be included in a rectifier device for converting direct current into alternating current in, e.g., photovoltaic generation. Such a rectifier device may be provided in a charging device, e.g., a charging device for vehicles. In such a case, it will be understood that the motor driving device, the rectifier device, the machine, the charging device, etc. which include the transformer5can easily be provided.

FIG. 12is a schematic view of a conventional transformer. In a transformer100shown inFIG. 12, coils171to173are disposed between two substantially E-shaped iron cores150and160. Thus, the coils171to173are disposed in parallel with each other.

InFIG. 12, when a magnetic flux passes through two adjacent coils as designated by wide arrows, magnetic fluxes outside the coils act, as designated by narrow arrows, on each other so as to cancel each other. This increases the magnetic resistance, and thus, there is a tendency that the direct-current resistance value of the coils of the transformer100shown inFIG. 12increases, and then, the loss increases.

FIG. 13is a schematic view of the transformer as shown inFIG. 2A. In this case, the two adjacent coils, e.g., coils52and53are not parallel to each other, and make an angle of approximately 120°. Thus, even if a magnetic flux passes through the two adjacent coils as designated by wide arrows, magnetic fluxes outside the coils do not cancel each other as designated by narrow arrows. Thus, in the transformer5of the present invention, the magnetic resistance does not increase. Thus, there is a tendency that the direct-current resistance values of the coils of the transformer5in the present invention do not largely increase, and an increase in the loss is small. It will be obvious that, as the angle between the two adjacent coils increases, the total loss does not needlessly increase without increasing the direct-current resistance values of the coils when the magnetic flux, which passes through the two adjacent coils, forms a closed magnetic path.

When an iron core is disposed between the two adjacent coils, an action for rectifying the flow of the magnetic fluxes occurring outside the coils is exerted, and accordingly, the direct-current resistance values of the coils can be further prevented from increasing. Thus, it is preferable to dispose an additional iron core in, e.g., an area A shown inFIG. 13. Here,FIG. 14is a sectional view of a transformer based on an eleventh embodiment of the present invention. InFIG. 14, an additional iron core45having a section formed like an isosceles triangle is disposed at a place corresponding to the area A inFIG. 13. As illustrated, the sides of the cross-sectional surface of the additional iron core45, which include a vertex angle, are larger than the thickness of the coils51and53.

InFIG. 14, the coils51and53are in contact with the inner surface of the outer peripheral iron core20. Thus, the coils51and53are surrounded by iron cores41and43, the outer peripheral iron core20, and the additional iron core45. In other words, three sides of each of the cross-sectional surfaces of the coils51and53are adjacent to the iron cores41and43, the outer peripheral iron core20, and the additional iron core45. In such a case, it will be understood that the aforementioned effect is high.

Further, inFIG. 14, protrusions20aand20bproject radially inward from the inner surface of the outer peripheral iron core20. The protrusions20aand20brespectively project between the coils51and52and between the coils52and53. The cross-sectional surfaces of the protrusions20aand20bare formed like a substantial isosceles trapezoid, and the protrusions20aand20bare partially in contact with the outer surfaces of the coils51and53.

As can be seen fromFIG. 14, the protrusion20ais in contact with the outer surfaces of the coils51and52. The same is true in the protrusion20b. Thus, in this case, two sides of the cross-sectional surface of each of the coils51and53are in fully contact with the corresponding one of the iron cores41and43and the outer peripheral iron core20, and one side of the cross-sectional surface of each of the coils51and53is in partially contact with the corresponding one of the protrusions20aand20b. In this case, it will be understood that an effect substantially similar to the aforementioned effect can be obtained. Note that there may be minute clearances between the coils and the additional iron core45or the protrusion parts20aand20b.

In the transformer5shown inFIG. 14, the additional iron core45may be disposed in all areas between the coils51to53. Alternatively, in the transformer5shown inFIG. 14, a protrusion similar to the aforementioned protrusions may be formed in all areas between the coils51to53.

FIG. 15is a sectional view of another transformer based on a twelfth embodiment of the present invention. InFIG. 15, additional iron cores41dto44dare disposed at the areas for the gaps101to104shown inFIG. 7. The cross-sectional surfaces of the additional iron cores41dto44dare shaped like a sector. Note that the cross-sectional surfaces of the additional iron cores41dto44dmay be shaped like an isosceles triangle.

The radially inside ends of the iron cores41to44are each comprised of two apical surfaces. As shown inFIG. 15, the two flat surfaces of each of the additional iron cores41dto44dare parallel to the corresponding apical surfaces of the adjacent iron cores. Further, gaps101ato104aand101bto104b, which can be magnetically coupled, are formed between the flat surfaces of the additional iron cores41dto44dand the corresponding apical surfaces of the iron cores41to44. Note that, it will be obvious that the angle between the two apical surfaces of each of the iron cores41to44inFIG. 15is less than 60 degrees.

The number of gaps inFIG. 15is eight, which is double the number of gaps shown inFIG. 7. Thus, the thickness of each gap, i.e., the distance between the flat surfaces of the additional iron cores41dto44dand the corresponding apical surfaces of the iron cores41to44can be reduced by half, and accordingly, the leakage flux can be reduced.

FIG. 16andFIG. 17are sectional views of transformers based on a thirteenth embodiment of the present invention.FIG. 16andFIG. 17show substantially square transformers5. As illustrated, iron cores42and44, which are opposed to each other, have a shape similar to the aforementioned shape.

In contrast, at the tips of the other iron cores41and43, wide portions41eand43e, which are wider than the main portions of the iron cores41and43, are provided. The shape of the wide portions41eand43ecorresponds to a part of a rhombus. However, the wide portions41eand43emay have another shape.

As illustrated, gaps101to104, which can be magnetically coupled, are formed between the wide portions41eand43eof the iron cores41and43and the iron cores42and44. The total length of the gaps101to104shown inFIG. 16is larger than the total length of the gaps of another transformer which has a similar shape having no wide portions. Thus, increasing the total length of gaps enables enhancement of the inductance.

In the transformer5shown inFIG. 17, iron cores41and43, which are opposed to each other, are entirely wider than the other iron cores42and44, which are opposed to each other. Thus, inFIG. 17, the tips of the opposed iron cores41and43are flat, and an additional gap105is formed between the iron cores41and43.

Thus, the total length of the gaps101to104and the additional gap105of the transformer5shown inFIG. 17is larger than the total length of the gaps of the transformer5in which the width of the iron cores41and43is similar to the width of the iron cores42and44. Likewise, in this case, the inductance can be enhanced.

FIG. 18is a sectional view of another transformer of the present invention. As shown inFIG. 18, the transformer5includes an outer peripheral iron core20, and four iron core coils31to34which are magnetically coupled to the outer peripheral iron core20. Further, a square central iron core80is disposed at the center of the transformer5. Note that the central iron core80does not have to be square, and is preferably line-symmetric or rotationally symmetric. The iron core coils are only required to be circumferentially arranged, and do not necessarily have to be arranged at equal intervals.

As can be seen fromFIG. 18, the iron core coils31to34respectively include iron cores41to44which radially extend, and coils51to54wound around the iron cores. The radially outside ends of the iron cores41to44are in contact with the outer peripheral iron core20, or are integral with the outer peripheral iron core20.

Further, the radially inside ends of the iron cores41to44are positioned in the vicinity of the center of the outer peripheral iron core20. InFIG. 18, the radially inside ends of the iron cores41to44are flat. The radially inside ends of the iron cores41to44are adjacent to the central iron core80via gaps101to104which can be magnetically coupled. Note that the dimensions of the gaps101to104are identical to one another.

In this case, the four iron core coils31to34are surrounded by the outer peripheral iron core20, and accordingly, magnetic fields occurring from the coils51to54do not leak to the outside of the outer peripheral iron core20. Further, a transformer including a central iron core80, which will be described later, has an effect substantially similar to the effect of the aforementioned transformers which have no central iron core80.

The transformer shown inFIG. 18and a transformer in another embodiment that will be described later have an effect that can adjust the inductance by changing the dimensions of the central iron core80. In other words, the gaps101to104having a given thickness can be provided at a low cost. This is advantageous in design to transformers having a conventional configuration.

FIG. 19is a sectional view of still another transformer of the present invention. In the following embodiment, an effect substantially similar to the effect of the transformer5shown inFIG. 18can be obtained. The radially inside ends of the iron cores41to44of the transformer5shown inFIG. 19converge on the center of the outer peripheral iron core20, and the tip angle of each end is approximately 90 degrees.

Further, a central iron core80is disposed at the center of the transformer5. As illustrated, the central iron core80has a substantially X-shape having four extensions81to84. Further, the iron cores41to44respectively have, in the vicinity of their radially inside ends, substantially sector-shaped protrusions41pto44p, which clockwise extend. The protrusions41pto44pextend in areas between the end faces of adjacent coils inFIG. 1. The shape of the apical surfaces of the iron cores41to44, to which the protrusions41pto44pare opposed, is configured to correspond to the protrusions41pto44p. Note that the protrusions41pto44pmay counterclockwise extend.

Both side faces of each of the extensions81to84are adjacent to the corresponding radially inside ends of the iron cores41to44. Further, gaps, which can be magnetically coupled, are formed between both side faces of the extensions81to84of the central iron core80and the iron cores41to44. Thus, the total length of the gaps increases, and consequently, the inductance can be enhanced.

FIG. 20is a sectional view of still another transformer of the present invention. The radially inside ends of the iron cores41to44converge on the center of the outer peripheral iron core20, and the tip angle of each end is approximately 90 degrees. However, as illustrated, the iron cores41and43are wider than the other iron cores42and44.

The transformer5shown inFIG. 20includes a substantially X-shaped central iron core80having four extensions81to84. The central iron core80is formed so that the radially inside ends of the iron cores41to44are received between two adjacent ones of the extensions81to84. Further, gaps, which can be magnetically coupled, are formed between both side faces of the extensions81to84of the central iron core80and the iron cores41to44. Thus, it will be understood that an effect similar to the aforementioned effect can be obtained.

FIG. 21is a sectional view of still another transformer of the present invention. The transformer5shown inFIG. 21includes an outer peripheral iron core20, a central iron core80having a substantially hexagonal shape, and iron core coils31to36similar to those described above. The iron core coils31to36respectively include iron cores41to46, which radially extend, and coils51to56wound around the iron cores.

The radially inside ends of the iron cores41to46of the transformer5shown inFIG. 21are flat. Further, the radially inside ends of the iron cores41to46are adjacent to the central iron core80via gaps101to106which can be magnetically coupled. As seen above, the transformer5may include iron core coils31to36, the number of which is an even number not less than 6.

FIG. 22is a sectional view of still another transformer of the present invention. The iron cores41to44, which extend in the radial directions of the iron core coils31to34in the transformer5shown inFIG. 22, respectively include first iron core portions41ato44apositioned on the radially inside, and third iron core portions41cto44cpositioned on the radially outside.

Iron core portion gaps111ato114a, which can be magnetically coupled, are formed between a central iron core80and first iron core portions41ato44a. Further, iron core portion gaps111bto114b, which can be magnetically coupled, are formed between the first iron core portions41ato44aand the third iron core portions41cto44c.

In such a case, for one iron core, e.g., the iron core41, the first iron core portion gap111aand the second iron core portion gap111bare formed, and accordingly, the thickness of each gap is small. The thickness of each gap can be reduced, and accordingly, the leakage flux from each gap can be reduced. Further, the iron cores41to44are each comprised of a plurality of iron core portions, and accordingly, the transformer5can be easily assembled. The iron cores41to44may be each comprised of three or more iron core portions arranged in a line.

FIG. 23is a sectional view of still another transformer of the present invention. InFIG. 23, additional iron cores41dto44dare each disposed between the corresponding two adjacent ones of iron cores41to43. The cross-sectional surface of each of the additional iron cores41dto44dis a part of a sector. Note that the cross-sectional surface of each of the additional iron cores41dto44dmay be a part of an isosceles triangle.

The radially inside ends of the iron cores41to44each include two apical surfaces and a flat surface between the two apical surfaces. As shown inFIG. 23, each of the two flat surfaces of each of the additional iron cores41dto44dis parallel to the corresponding apical surface of the adjacent iron core. Gaps101ato104aand101bto104b, which can be magnetically coupled, are formed between the flat surfaces of the additional iron cores41dto44dand the corresponding apical surfaces of the iron cores41to44. Further, gaps101to104, which can be magnetically coupled, are formed between the flat surfaces of the iron cores41to44and the central iron core80. Further, gaps (having no reference numerals), which can be magnetically coupled, are formed between the tips of the additional iron cores41dto44dand the central iron core80.

InFIG. 23, the total length of the gaps is increased, and accordingly, the inductance can be increased. Further, in this case, the thickness of each gap can be reduced, and accordingly, the leakage flux can be further reduced.

FIG. 24is a sectional view of still another transformer of the present invention. In the transformer5shown inFIG. 24, outer peripheral iron core gaps111cto114c, which can be magnetically coupled, are respectively formed between the radially outside ends of iron cores41to44and an outer peripheral iron core20. When the transformer5operates, heat occurs in the iron core coils31to34. In this embodiment, the outer peripheral iron core gaps111cto114care formed, and accordingly, the heat occurring from the iron core coils31to34is difficult to transfer to the outer peripheral iron core20.

FIG. 25is a sectional view of a transformer based on a sixth embodiment of the present invention. In the transformer5shown inFIG. 25, an outer peripheral iron core20is comprised of a plurality of, e.g., four outer peripheral iron core portions21to24. InFIG. 25, the outer peripheral iron core portion21is in contact with or integral with an iron core41. Likewise, the outer peripheral iron core portions22to24are respectively in contact with or integral with iron cores42to44. In the embodiment shown inFIG. 25, even if the outer peripheral iron core20is large, such an outer peripheral iron core20can be easily produced.

FIG. 26is a sectional view of another transformer of the present invention. In the transformer5shown inFIG. 26, outer peripheral iron core portions21to24are disposed via outer peripheral iron core portion gaps61to64. In such a case, the outer peripheral iron core portion gaps61to64can be adjusted by adjusting the lengths of the outer peripheral iron core portions21to24. Consequently, it will be understood that the unbalance of the inductance of transformer5can be adjusted.

The transformer5shown inFIG. 26differs from the transformer5shown inFIG. 25only in that it has the outer peripheral iron core portion gaps61to64. In the embodiments shown inFIG. 25andFIG. 26, even if the outer peripheral iron core20is large, such an outer peripheral iron core20can be easily produced.

FIG. 27is a sectional view of still another transformer of the present invention. In the transformer5shown inFIG. 27, the sectional areas of coils51and54of iron core coils31and34are larger than the sectional areas of coils52and53of iron core coils32and33. Further, iron cores41and44of the iron core coils31and34are narrower than iron cores42and43of the iron core coils32and33. Note that the dimensions of gaps101to104are equal to one another.

In other words, as designated by two-dot chain lines inFIG. 27, the transformer5includes a first set comprised of two iron core coils31and34and a second set comprised of the other two iron core coils32and33. The first set and the second set each include two adjacent ones of the four iron core coils31to34. In the transformer5shown inFIG. 27, the dimensions of the iron cores, the sectional areas of the coils, and the number of turns differ between the first set and the second set. Note that, in the transformer5, the dimensions of the gaps in the first set may be different from those in the second set.

Thus, two transformers having different properties can substantially be included in one transformer5. Thus, the installation space for two transformers having different properties can be reduced. Further, it will be understood that connecting two transformers in series or in parallel enables adjustment of the inductance value.

FIG. 28is a sectional view of still another transformer of the present invention. In the transformer5shown inFIG. 28, iron cores41and42are wider than iron cores45and46, and the iron cores45and46are wider than iron cores43and44. Further, the sectional areas of coils51and52wound around the iron cores41and42are smaller than the sectional areas of coils55and56wound around the iron cores45and46, and the sectional areas of the coils55and56are smaller than the sectional areas of coils53and54wound around the iron cores43and44.

Thus, as designated by two-dot chain lines inFIG. 28, the transformer5includes a first set comprised of two iron core coils31and32, a second set comprised of another two iron core coils33and34, and a third set comprised of still another two iron core coils35and36. The first to third sets each include two adjacent ones of the six iron core coils31to36.

In the transformer5shown inFIG. 28, the dimensions of the iron cores, the sectional areas of the coils, and the number of turns differ among the first to third sets. Note that, in the transformer5, the dimensions of the gaps in the first set may be different from those in the other sets. It will be understood that such a configuration brings about an effect similar to the effect in the embodiment shown inFIG. 27. Alternatively, four or more transformers having different properties or the same property, i.e., four or more sets described above may be included in one transformer5. It will be obvious that, even in this case, a similar effect can be obtained.

Disclosure of Aspects

According to a first aspect, there is provided a transformer including an outer peripheral iron core, and at least three iron core coils, which are in contact with or coupled to the inner surface of the outer peripheral iron core. The at least three iron core coils each include an iron core, and at least one of a primary coil and a secondary coil, which are wound around the iron core. Gaps, which can be magnetically coupled, are formed between two adjacent ones of the at least three iron cores, or between the at least three iron cores and a central iron core positioned at the center of the outer peripheral iron core.

According to a second aspect, in the transformer according to the first aspect, the number of the at least three iron core coils is a multiple of 3.

According to a third aspect, in the transformer according to the first aspect, the number of the at least three iron core coils is an even number not less than 4.

According to a fourth aspect, in the transformer according to any of the first to third aspects, the iron core is comprised of a plurality of iron core portions.

According to a fifth aspect, in the transformer according to the fourth aspect, iron core portion gaps, which can be magnetically coupled, are each formed between adjacent ones of the plurality of iron core portions.

According to a sixth aspect, in the transformer according to any of the first to fifth aspects, the outer peripheral iron core is comprised of a plurality of outer peripheral iron core portions.

According to a seventh aspect, in the transformer according to the sixth aspect, outer peripheral iron core portion gaps, which can be magnetically coupled, are each formed between adjacent ones of the plurality of outer peripheral iron core portions.

According to an eighth aspect, in the transformer according to any of the first to seventh aspects, outer peripheral iron core gaps, which can be magnetically coupled, are formed between the iron cores of the at least three iron core coils and the outer peripheral iron core.

According to a ninth aspect, in the transformer according to any of the first to eighth aspects, a gap material or insulating paper, which is a non-magnetic material or resin, is inserted or charged into the gaps, the iron core portion gaps, the outer peripheral iron core portion gaps, or the outer peripheral iron core gaps in the transformer.

According to a tenth aspect, in the transformer according to any of the first to ninth aspects, a gap material or insulating material, which is a non-magnetic material or resin, is charged into the inside of the outer peripheral iron core in the transformer.

According to an eleventh aspect, there is provided a motor driving device including the transformer according to any of the first to tenth aspects.

According to a twelfth aspect, there is provided a machine including the motor driving device according to the eleventh aspect.

According to a thirteenth aspect, there is provided a rectifier device including the transformer according to any of the first to tenth aspects.

According to a fourteenth aspect, there is provided a machine including the rectifier device according to the thirteenth aspect.

Effects of Aspects

In the first aspect, the iron core coils each obtained by winding a winding around an iron core are disposed inside the outer peripheral iron core, and accordingly, the leakage flux from the winding to the circumference can be reduced. Further, providing a shield plate as in a conventional technology is not necessary, and a small transformer can be formed.

Further, in a three-phase transformer, the magnetic path lengths of the three phases are structurally equal, and accordingly, the design and production can be easily performed. Furthermore, the ratio of the primary input voltage to the secondary output voltage is fixed, and accordingly, a control line is not necessary, and the size of the transformer can be further reduced.

In the second aspect, the transformer can be used as a three-phase transformer.

In the third aspect, the transformer can be used as a single-phase transformer.

In the fourth aspect, the coils can be easily attached, and the assembling property of the transformer can be improved.

In the fifth aspect, the gaps between the iron core coils and the iron core portion gaps between the iron core portions are both formed, and accordingly, the dimensions of each gap can be reduced. Thus, the magnetic flux leaking from the gaps can be reduced, and accordingly, the eddy current loss within each coil due to the leaked magnetic flux can be reduced.

In the sixth aspect, the coils can be easily attached, and the assembling property of the transformer can be improved. This is advantageous to making, specifically, a large transformer.

In the seventh aspect, the unbalance of the inductance can be easily adjusted by adjusting the outer peripheral iron core portion gaps.

In the eighth aspect, the outer peripheral iron core gaps are formed between the outer peripheral iron core and the iron core coils, and accordingly, the heat occurring from the iron core coils is difficult to transfer to the outer peripheral iron core.

In the ninth aspect, the oscillation of the iron cores, which are in contact with the gaps, can be reduced, and the noises occurring from the iron cores can be reduced.

In the tenth aspect, the temperature equilibration between the iron core coils and the outer peripheral iron core is promoted, and the noises occurring from the iron core coils or the outer peripheral iron core can be reduced.

In the eleventh to fourteenth aspects, the motor driving device, the machine, and the rectifier device, which include the transformer, can be easily provided.

The present invention has been described above using exemplary embodiments. However, a person skilled in the art would understand that the aforementioned modifications and various other modifications, omissions, and additions can be made without departing from the scope of the present invention. Any appropriate combination of these embodiments is included in the scope of the present invention.