Patent Publication Number: US-2020294705-A1

Title: Iron core including first iron core block and second iron core block

Description:
RELATED APPLICATIONS 
     The present application is a divisional of U.S. patent application Ser. No. 15/919,800, filed Mar. 13, 2018, which claims priority to Japanese Application Number 2017-053579, filed Mar. 17, 2017, the disclosures of which are hereby incorporated by reference herein in their entireties. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an iron core including a first iron core block and a second iron core block. 
     2. Description of Related Art 
     In iron cores according to the prior art, a gap member is disposed between a first iron core block and a second iron core block (for example, refer to Japanese Unexamined Patent Publication (Kokai) Nos. 59-15363, 59-19457, and 2-15301). 
     SUMMARY OF THE INVENTION 
     Gap members are generally made of resin materials, and therefore have relatively large dimensional tolerances on the order of ±0.1 mm. When a gap between a first iron core block and a second iron core block is of the order of 1 mm to 2 mm, the dimensional tolerance of the gap member has a large effect on the inductance of a reactor having the iron core. 
     Gap members are often secured to iron core blocks with adhesives or bands. In other words, the gap members are neither directly nor tightly secured to the iron core blocks, and this causes noise or vibration. For the purpose of securing the gap members with bolts or the like, forming through holes in the iron core blocks causes an increase in iron loss. 
     Therefore, it is desired to provide an iron core that has a reduced effect on inductance, without an increase in noise, vibration, and iron loss. 
     A first aspect of this disclosure provides an iron core that includes a first iron core block and a second iron core block disposed so as to create a gap therebetween, and a non-magnetic fastener disposed in the gap. The fastener joins the first iron core block and the second iron core block to each other. 
     According to the first aspect, the fastener that joins the first iron core block and the second iron core block to each other prevents an increase in noise, vibration, and iron loss. Since the iron core blocks need not be machined in a specific manner, an effect on inductance is eliminated. 
     The above objects, features, and advantages and other objects, features, and advantages of the present invention will become more apparent from the following detailed description of preferred embodiments along with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional view of a reactor including an iron core according to a first embodiment; 
         FIG. 2A  is a partial enlarged side cross-sectional view of a fastener and the vicinity thereof according to the first embodiment; 
         FIG. 2B  is a cross-sectional view taken along line A-A in  FIG. 2A ; 
         FIG. 2C  is a drawing of an example of the fastener; 
         FIG. 2D  is a drawing of another example of the fastener; 
         FIG. 2E  is a drawing of yet another example of the fastener; 
         FIG. 3  is a cross-sectional view of an iron core block according to a second embodiment; 
         FIG. 4A  is a top view of an iron core block according to the prior art; 
         FIG. 4B  is a top view of an iron core block according to a third embodiment; 
         FIG. 4C  is a top view of another iron core block according to the prior art; 
         FIG. 4D  is a top view of another iron core block according to the third embodiment; 
         FIG. 5A  is a cross-sectional view of an iron core block according to a fourth embodiment; 
         FIG. 5B  is another cross-sectional view of the iron block according to the fourth embodiment; 
         FIG. 6  is a cross-sectional view of another reactor including an iron core; and 
         FIG. 7  is a cross-sectional view of yet another reactor including an iron core. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Embodiments of the present invention will be described below with reference to the accompanying drawings. In the drawings, the same reference numerals indicate the same components. For ease of understanding, the scales of the drawings have been modified in an appropriate manner. 
       FIG. 1  is a cross-sectional view of a reactor including an iron core according to a first embodiment. As shown in  FIG. 1 , the reactor  5  includes an outer peripheral core  20  having a hexagonal cross-section, and at least three core coils  31  to  33  contacting or connected to an inner surface of the outer peripheral core  20 . The outer peripheral core  20  may have a round shape or another polygonal shape. 
     The core coils  31  to  33  include cores  41  to  43  and coils  51  to  53  wound onto the cores  41  to  43 , respectively. Each of the outer peripheral core  20  and the cores  41  to  43  is made by stacking iron sheets, carbon steel sheets, electromagnetic steel sheets, or amorphous sheets, or made of a magnetic material such as a pressed powder core or ferrite. The number of the core coils  31  to  33  may be an integral multiple of 3, and thereby the iron core assembly constituted of the outer peripheral core  20  and the cores  41  to  43  can be used in a three-phase reactor. 
     Furthermore, the cores  41  to  43  converge toward the center of the outer peripheral core  20  at their radial inner end portions, each having an edge angle of approximately 120°. The radial inner end portions of the cores  41  to  43  are separated from each other by gaps  101   a  to  103   a , which can be magnetically coupled. In other words, in the first embodiment, the radial inner end portion of the core  41  is separated from the radial inner end portions of the two adjacent cores  42  and  43  by the gaps  101   a  and  103   a , respectively. The same is true for the other cores  42  and  43 . 
     Furthermore, the cores  41  to  43  have the same dimensions as each other, and are arranged at equal intervals in the circumferential direction of the outer peripheral core  20 . In  FIG. 1 , gaps  101   b  to  103   b  are each formed between the radial outer end portion of each of the cores  41  to  43  and the outer peripheral core  20 , so as to be magnetically coupled. 
     Note that, the gaps  101   a  to  103   a  ideally have the same dimensions, but may have different dimensions. The same is true for the gaps  101   b  to  103   b . In the embodiments described later, a description regarding the gaps  101   a  to  103   a , the core coils  31  to  34 , and the like may be omitted. 
     As described above, in the first embodiment, the core coils  31  to  33  are disposed inside the outer peripheral core  20 . In other words, the core coils  31  to  33  are enclosed within the outer peripheral core  20 . The outer peripheral core  20  can reduce leakage of magnetic flux generated by the coils  51  to  53  to the outside. 
     Fasteners  61  to  63  are each disposed between each of the cores  41  to  43  and the outer peripheral core  20 . The centers of the fasteners  61  to  63  are disposed in the gaps  101   b  to  103   b , respectively. Each of the fasteners  61  to  63  serves to join each of the cores  41  to  43  and the outer peripheral core  20  together. 
     A fastener  60  is disposed at the center of the reactor  5 . The center of the fastener  60  is disposed at the intersection of the gaps  101   a  to  103   a . The fastener  60  serves to join the cores  41  to  43  to each other. The fasteners are made of a non-magnetic material, e.g., SUS, aluminum, or the like. 
       FIG. 2A  is a partial enlarged side cross-sectional view of a fastener and the vicinity thereof according to the first embodiment, and  FIG. 2B  is a cross-sectional view taken along line A-A in  FIG. 2A . In the drawings, the fastener  65  joins a first iron core block B 1  and a second iron core block B 2  to each other. The fastener  65  is a typical example of the fasteners  60  and  61  to  63  ( 64 ). The gap  100  is a typical example of the gaps  101   a  to  103   a  ( 104   a ), and  101   b  to  103   b  ( 104   b ).  FIG. 2B  illustrates the gap length G of the gap  100 , which corresponds to the distance between the first iron core block B 1  and the second iron core block B 2 . 
     When the fastener  65  represents the fasteners  61  to  63 , the first iron core block B 1  corresponds to the outer peripheral core  20 , and the second iron core block B 2  corresponds to the cores  41  to  43 . When the fastener  65  represents the fastener  60 , the first iron core block B 1  and the second iron core block B 2  correspond to the cores  41  to  43 . 
     Furthermore,  FIG. 2C  is a drawing of an example of the fastener illustrated in  FIG. 2A . The fastener  65  illustrated in  FIG. 2C  is constituted of a bolt  71  and a nut  72 . Referring to  FIGS. 2A and 2B , the shaft  71   a  is longer than the thicknesses of the first iron core block B 1  and the second iron core block B 2 , and the shaft  71   a  of the bolt  71  has a regular hexagonal cross-section. The shaft  71   a  may have another polygonal cross-section or a round cross-section. Each of the head portion of the bolt  71  and the nut  72  has a larger diameter than the gap length G. 
     In this instance, after the shaft  71   a  of the bolt  71  is inserted into the gap  100 , the nut  72  is screwed onto the bolt  71  on the end opposite to the head. Thus, the fastener  65  firmly joins the first iron core block B 1  and the second iron core block B 2  to each other. As shown in  FIG. 2B , the dimensions of the shaft  71   a  are determined such that the maximum turning radius of the cross-section of the shaft  71   a  is equal to or more than half of the gap length G. 
     Therefore, once the fastener  65  has joined the first iron core block B 1  and the second iron core block B 2  to each other, the bolt  71  does not turn in the gap  100 . Therefore, even when a device, e.g., a reactor  5 , including an iron core constituted of the first iron core block B 1  and the second iron core block B 2  is driven, no noise or vibration occurs from the first iron core block B 1  and the second iron core block B 2 . Through holes or the like need not be formed in the first iron core block B 1  and the second iron core block B 2 , thus resulting in no increase in iron loss. 
     Furthermore, since the fastener  65  made of the non-magnetic material firmly joins the first iron core block B 1  and the second iron core block B 2 , a gap member made of a resin material or the like need not be used. Thus, the gap length G of the gap  100  is defined by machining accuracy for machining the iron core blocks B 1  and the like and the fastener  65 , for example, a dimensional tolerance of the order of ±0.02 mm. Furthermore, the iron core blocks B 1  and B 2  need not be machined in a specific manner. Therefore, it is possible to eliminate an effect on the inductance of the reactor  5 . 
     When the fastener  65  includes a screw, a bolt, or the like, the fastener  65  can join the iron core blocks B 1  and B 2  for a longer time than when using an adhesive. Furthermore, since the bolt and the like made of the non-magnetic material hardly interfere with magnetic flux passing through the iron core, the iron core including the iron core blocks B 1  and B 2  does not grow in size. 
       FIGS. 2D and 2E  illustrate other examples of the fastener. The fastener  65  illustrated in  FIG. 2D  is constituted of a rod  74  having inner threads formed in both end surfaces of the rod  74 , and two screws  73 . The fastener  65  illustrated in  FIG. 2E  is constituted of a rod  74  having threads protruding from both end surfaces of the rod  74 , and two nuts  72 . The cross-section of each rod  74  is similar to that of the shaft  71   a  of the bolt  71 . In these instances, the fasteners  65  are made of the above-described non-magnetic material. Therefore, the same effects as above can be obtained. 
       FIG. 3  is a top view of an iron core block according to a second embodiment, when viewed in the same manner as  FIG. 2B . In  FIG. 3 , recessed portions  75  are formed in a surface of a first iron core block B 1  and a surface of a second iron core block B 2  facing a gap  100 , into a shape corresponding to the fastener  65 . The cross-section of the recessed portion  75  may be in any shape other than a semicircle. The recessed portion  75  may be formed in the surface of only one of the first iron core block B 1  and the second iron core block B 2 . 
     An existing bolt  71  to be used as the fastener  65  may have unsuitable dimensions for the gap length G. For example, the maximum turning radius of the existing bolt  71 , which can be used as the fastener  65 , may be larger than a half of the gap length G. In such an instance, a recessed portion  75  may be formed in at least one of a first iron core block B 1  and a second iron core block B 2 , and the existing bolt  71  can be thereby disposed in a gap  100  having the desired gap length G. 
     In other words, a fastener  65  of desired dimensions can be used, irrespective of the gap length G of the gap  100 . The recessed portion  75  preferably has a minimum shape corresponding to the fastener  65 , and, as a result, produces a reduced effect on inductance. 
       FIG. 4A  is a top view of an iron core block according to the prior art. In  FIG. 4A , the thick lines represent the surfaces of the first iron core block B 1  and the second iron core block B 2  forming the gap  100 . When the reactor  5  is driven, the main magnetic flux passes through the surfaces of the first iron core block B 1  and the second iron core block B 2  represented by the thick lines. However, when the fastener  65  (not illustrated in  FIG. 4A ) is disposed in the gap  100 , the gap  100  is reduced in size by the fastener  65 , and hence the size (cross-sectional area) of the gap  100  is reduced with respect to the sizes (cross-sectional areas) of the iron core blocks B 1  and B 2 , through which the main magnetic flux passes. 
       FIG. 4B  is a top view of an iron core block according to a third embodiment. In  FIG. 4B , gap extension portions  81  are provided on both side surfaces of each of the first iron core block B 1  and the second iron core block B 2 . The gap extension portions  81  are formed on the surfaces of each of the first iron core block B 1  and the second iron core block B 2  adjacent to the surface forming the gap  100 . The gap extension portions  81  serve to extend the gap  100  in part of the iron core blocks B 1  and B 2 . The gap extension portions  81  are preferably formed integrally with the first iron core block B 1  and the second iron core block B 2 . 
     In  FIG. 4B , a fastener  65  disposed in the gap  100  divides the gap  100  into a first gap portion  100   a  and a second gap portion  100   b . The dimensions of the gap extension portions  81  are determined such that the sum of the dimension L 1  of the first gap portion  100   a  and the dimension L 2  of the second gap portion  100   b  is equal to the dimension L 0  (width) of the gap  100 . In  FIG. 4B , the gap extension portions  81  have the same dimension as each other. 
     In other words, the maximum width of the gap extension portions  81  provided on both of the side surfaces of the first iron core block B 1  and the like is substantially equal to the sum of the dimension L 1  of the first gap portion  100   a , the dimension L 2  of the second gap portion  100   b , and the diameter of a shaft  71   a  of a bolt  71 . Furthermore, the dimensions of the gap extension portions  81  may be different between one side of the iron core block and the other side thereof, as long as the sum of the dimension L 1  of the first gap portion  100   a  and the dimension L 2  of the second gap portion  100   b  is equal to the dimension L 0  of the gap  100 . 
     As described above, the provision of the gap extension portions  81  can compensate for the reduced size of the gap  100  owing to the disposition of the fastener  65 . As a result, the electrical characteristics of the reactor  5  are prevented from changing. In order to obtain desired electrical characteristics, the dimensions of the gap extension portions  81  may be changed. 
       FIG. 4C  is a top view of another iron core block according to the prior art.  FIG. 4D  is a top view of another iron core block according to the third embodiment. In these drawings, the first iron core block B 1  is smaller than the second iron core block B 2 . 
     In this instance, as shown in  FIG. 4D , a smaller first iron core block B 1  is partly projected, while a larger second iron core block B 2  is partly recessed in accordance with the first iron core block B 1 . In  FIG. 4D , the first iron core block B 1  includes a trapezoidal projected portion  82 , while the second iron core block B 2  includes a trapezoidal recessed portion  83 . The trapezoidal projected portion  82  and the trapezoidal recessed portion  83  are examples of the gap extension portion  81 . Note that, the trapezoidal projected portion  82  and the trapezoidal recessed portion  83  may be formed in other shapes. 
     As shown in  FIG. 4D , the dimensions of the trapezoidal projected portion  82  are determined such that the sum of the dimensions L 3  to L 6  of individual parts of the trapezoidal projected portion  82  after a fastener  65  is disposed in a gap  100  is equal to the dimension L 0  of a surface of a first iron core block B 1  facing the gap  100  illustrated in  FIG. 4C . In the same manner, the dimensions of the trapezoidal recessed portion  83  are determined, such that the sum of the dimensions L 7  to L 10  of individual parts of the trapezoidal recessed portion  83 , after the fastener  65  is disposed in the gap  100 , is equal to the dimension L 0  of part of a surface of a second iron core block B 2  facing the gap  100  illustrated in  FIG. 4C . In this instance, the same effects as above can be obtained. 
       FIG. 5A  is a cross-sectional view of an iron core block according to a fourth embodiment, when viewed in the same manner as  FIG. 2B . For ease of understanding,  FIG. 5A  and  FIG. 5B , which is described later, omit a nut  72 . In the drawings, the bolt  71  to be used as the fastener  65  is round in cross-section, and has a diameter approximately equal to the gap length G. 
     In  FIG. 5A , a projection  76  is provided in the shaft  71   a  of the bolt  71 , as an anti-rotation member. Once the fastener  65  has joined the first iron core block B 1  and the second iron core block B 2 , the bolt  71  of the fastener  65  cannot rotate due to the projection  76 . Therefore, the projection  76  prevents the loosening of the fastener  65 . 
       FIG. 5B  is another cross-sectional view of the iron block according to the fourth embodiment, when viewed in the same manner as  FIG. 5A . In  FIG. 5B , a receptacle  77 , e.g., a pit, for receiving the projection  76  is formed in the second iron core block B 2 , in addition to the projection  76  formed in the shaft  71   a  of the bolt  71 . In  FIG. 5B , both the projection  76  and the receptacle  77  function as anti-rotation members. In this instance, the bolt  71  is disposed in the gap  100  in such a direction that the projection  76  is fitted into the receptacle  77 . In this instance, the bolt  71  of the fastener  65  cannot rotate, thus producing the same effects as above. 
     Though not illustrated, the receptacle  77  may be formed in the shaft  71   a , while the projection  76  may be formed in the second iron core block B 2 . The fourth embodiment includes instances in which a plurality of anti-rotation members are provided. 
       FIG. 6  is a cross-sectional view of another reactor including an iron core. As shown in  FIG. 6 , the reactor  5  mainly includes an outer peripheral core  20  and a central core  10  disposed inside the outer peripheral core  20 . The central core  10  includes three extension portions  11  to  13  arranged at equal intervals in the circumferential direction. The extension portions  11  to  13  constitute part of the central core  10 . In  FIG. 6 , the extension portions  11  to  13  and coils  51  to  53 , which are wound onto the extension portions  11  to  13 , constitute core coils  31  to  33 , respectively. 
     Fasteners  61  to  63  are each disposed between each of the extension portions  11  to  13  and the outer peripheral core  20 . The centers of the fasteners  61  to  63  are disposed in gaps  101   b  to  103   b , which can be magnetically coupled. The fasteners  61  to  63  serve to join each of the extension portions  11  to  13  and the outer peripheral core  20  to each other. 
       FIG. 7  is a cross-sectional view of yet another reactor including an iron core. As shown in  FIG. 7 , the reactor  5  includes an approximately octagonal outer peripheral core  20  and four core coils  31  to  34 , which are similar to the above-described core coils, disposed inside the outer peripheral core  20 . The core coils  31  to  34  are arranged at equal intervals in the circumferential direction of the reactor  5 . The number of cores is preferably an even number of 4 or more, and thereby the reactor  5  can be used as a single-phase reactor. 
     As is apparent from the drawing, the core coils  31  to  34  include cores  41  to  44  and coils  51  to  54  wound onto the cores  41  to  44 , respectively. Gaps  101   b  to  104   b  are each formed between the radial outer end portion of each of the cores  41  to  44  and the outer peripheral core  20 , so as to be magnetically coupled. 
     Furthermore, the radial inner end portion of each of the cores  41  to  44  is disposed in the vicinity of the center of the outer peripheral core  20 . In  FIG. 7 , the cores  41  to  44  converge toward the center of the outer peripheral core  20  at their radial inner end portions, each having an edge angle of approximately 90°. The radial inner end portions of the cores  41  to  44  are separated from each other by gaps  101   a  to  104   a , which can be magnetically coupled. 
     Fasteners  61  to  64  are each disposed between each of the cores  41  to  44  and the outer peripheral core  20 . The centers of the fasteners  61  to  64  are disposed in the gaps  101   b  to  104   b , which can be magnetically coupled, respectively. The fasteners  61  to  64  serve to join each of the cores  41  to  44  and the outer peripheral core  20  to each other. Furthermore, a fastener  60  is disposed at the center of the reactor  5 . The center of the fastener  60  is disposed at the intersection of the gaps  101   a  to  104   a . The fastener  60  serves to join the cores  41  to  44  to each other. The embodiments illustrated in  FIGS. 6 and 7  produce the same effects as above. 
     The reactors  5  are described with reference to the drawings, but this disclosure includes potential transformers having the same structure as above. Furthermore, this disclosure includes appropriate combinations of some of the above-described embodiments. 
     ASPECTS OF THE DISCLOSURE 
     A first aspect provides an iron core that includes a first iron core block (B 1 ) and a second iron core block (B 2 ) disposed so as to create a gap ( 100 ) therebetween; and a non-magnetic fastener ( 65 ) disposed in the gap, for joining the first iron core block and the second iron core block to each other. 
     According to a second aspect, in the first aspect, a recessed portion ( 75 ) corresponding to the fastener is formed in at least one of the first iron core block and the second iron core block. 
     According to a third aspect, in the first or second aspect, at least one of part of the first iron core block facing the gap and part of the second iron core block facing the gap includes a gap extension portion ( 81 ) for extending the gap. 
     A fourth aspect further includes an anti-rotation member ( 76 ,  77 ) for preventing rotation of the fastener in the gap, in any one of the first to third aspects. 
     According to a fifth aspect, in any one of the first to fourth aspects, a plurality of the second iron core blocks are disposed inside the first iron core block of a ring shape, and a coil is wound onto each of the second iron core blocks. 
     According to a sixth aspect, in the fifth aspect, the number of the second iron core blocks having the coils wound thereon is an integral multiple of 3. 
     According to a seventh aspect, in the fifth aspect, the number of the second iron core blocks having the coils wound thereon is an even number of 4 or more. 
     Advantageous Effects of the Aspects 
     According to the first aspect, the fastener that joins the first iron core block and the second iron core block to each other prevents an increase in noise, vibration, and iron loss. The iron core blocks need not be machined in a specific manner, and therefore produce no effect on inductance. 
     The second aspect allows the use of a fastener of desired dimensions, irrespective of the dimensions of the gap. Since the recessed portion has a minimum shape corresponding to the fastener, the effect on inductance can be reduced. 
     When the fastener is disposed, the size of the gap is reduced with respect to the sizes (cross-sectional areas) of the iron core blocks, through which the main magnetic flux passes. The provision of the gap extension portion can compensate for the reduced size of the gap in the third aspect. 
     According to the fourth aspect, the anti-rotation member prevents rotation of the fastener. This prevents the loosening of the fastener. The anti-rotation member is preferably, for example, a projection, and the anti-rotation member may include a pit for receiving the projection. The anti-rotation member may be provided in the fastener, the first iron core block, or the second iron core block. 
     According to the fifth aspect, the iron core can be used in a reactor. 
     According to the sixth aspect, the iron core can be used in a three-phase reactor. 
     According to the seventh aspect, the iron core can be used in a single-phase reactor. 
     The present invention has been described above with reference to the preferred embodiments, but it is apparent for those skilled in the art that the above modifications and various other modifications, omissions, and additions can be performed without departing from the scope of the present invention.