Patent Publication Number: US-2018040408-A1

Title: Reactor

Description:
TECHNICAL FIELD 
     The present invention relates to a reactor, a passive element utilizing an inductance. 
     BACKGROUND ART 
     PTL1 discloses a reactor in which the cross-sectional area of a part of a core around which a coil is wound is larger than the cross-sectional area of a part of the core where the coil is not wound for the purpose of providing the reactor with a small size and improving a DC superposition characteristic for a large current flowing to the reactor. 
     PTL2 discloses a reactor in which the length of a core where a coil is not wound can be changed for the purpose of making inductance adjustable with a simple structure. 
     PTL3 discloses a reactor in which the ratio of a length of a part of a core around which a coil is wound to the length of a part of the core where the coils not wound is determined for the purpose of balanced installation and facilitating assembly. 
     CITATION LIST 
     Patent Literature 
     PTL1: Japanese Patent Laid-Open Publication No. 2007-243136 
     PTL2: Japanese Patent Laid-Open Publication No. 11-23826 
     PTL3: Japanese Patent Laid-Open Publication No. 2009-259971 
     SUMMARY 
     A reactor includes a core made of magnetic material and a coil wound around a part of the core. The core includes a first core part having both ends opposite to each other, a second core part having both ends opposite to each other, a third core part having both ends opposite to each other, and a fourth core part having both ends opposite to each other. One end of the both ends of the first core part is connected to one end of the both ends of the third core part. Another end of the both ends of the third core part is connected to one end of the both ends of the second core part. Another end of the both ends of the second core part is connected to one end of the both ends of the fourth core part. Another end of the both ends of the fourth core part is connected to another end of the both ends of the first core part. The coil includes a first coil part wound around a part of the first core part, and a second coil part wound around a part of the second core part. The first core part includes a first winding part around which the first coil part is wound, a first region extending from the one end of the both ends of the first core part to the first winding part, and a second region extending from the another end of the both ends of the first core part to the first winding part. The first coil part is not wound around the first region. The first coil part is not wound around the second region. The second core part includes a second winding part around which the second coil part is wound, a third region extending from the one end of the both ends of the second core part to the second winding part, and a fourth region extending from the another end of the both ends of the second core part to the second winding part. The second coil part is not wound around the third region. The second coil part is not wound around the fourth region. The third core part, the first region of the first core part, and the third region of the second core part constitute a first non-winding part. The fourth core part, the second region of the first core part, and the fourth region of the second core part constitute a second non-winding part. A cross-sectional area S 1  of the first core part perpendicular to a direction of a magnetic flux passing through the first core part, a cross-sectional area S 2  of the second core part perpendicular to a direction of a magnetic flux passing through the second core part, a cross-sectional area S 3  of the third core part perpendicular to a direction of a magnetic flux passing through the third core part, a cross-sectional area S 4  of the fourth core part perpendicular to a direction of a magnetic flux passing through the fourth core part, a length A 1  of the first winding part, a length A 2  of the second winding part, a length B 1  of the first non-winding part, and a length B 2  of the second non-winding part satisfy following relations: A 1 +A 2 &lt;B 1 +B 2 ; S 1 &gt;S 3 ; S 1 &gt;S 4 ; S 2 &gt;S 3 ; and S 2 &gt;S 4 . 
     This reactor reduces influence of heat and has a small size. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a perspective view of a reactor in accordance with Exemplary Embodiment 1. 
         FIG. 2  is a cross-sectional view of the reactor along line II-II shown in  FIG. 1   
         FIG. 3  is a cross-sectional view of the reactor in accordance with Embodiment 1. 
         FIG. 4  is a cross-sectional view of the reactor along line IV-IV shown in  FIG. 1 . 
         FIG. 5  is a cross-sectional view of the reactor along line V-V shown in  FIG. 1 . 
         FIG. 6A  shows characteristics of the reactor in accordance with Embodiment 1. 
         FIG. 6B  shows an alternating-current loss of the reactor in accordance with Embodiment 1. 
         FIG. 7  is a cross-sectional view of a reactor in accordance with Exemplary Embodiment 2. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENT 
     Exemplary Embodiment 1 
       FIG. 1  is a perspective view of reactor  10  in accordance with Exemplary Embodiment 1.  FIG. 2  is a cross-sectional view of reactor  10  along line II-II shown in  FIG. 1  for illustrating a cross section of reactor  10  parallel to an XY plane.  FIG. 3  is a cross-sectional view of reactor  10 .  FIG. 4  is cross-a sectional view of reactor  10  along line IV-IV shown in  FIG. 1  for illustrating a cross section of reactor  10  parallel to an XZ plane.  FIG. 5  is a cross-sectional view of reactor  10  along line V-V shown in  FIG. 1  for illustrating a cross section of reactor  10  parallel to a YZ plane. 
     Reactor  10  includes core  20  and coil  30 . 
     Core  20  is made of magnetic material. Core  20  includes core part  21 , core part  22 , core part  23 , and core part  24 . Core part  21  is connected to core part  23 . Core part  23  is connected to core part  22 . Core part  22  is connected to core part  24 . Core part  24  is connected to core part  21 . Core parts  21 ,  22 ,  23 , and  24  are all made of the magnetic material. Core  20  has a rectangular annular shape. Reactor  10  has a smaller size than a reactor including a core, such as an EI type core, having another shape. 
     Core part  21  has both ends  21   a  and  21   b  opposite to each other. Core part  22  has both ends  22   a  and  22   b  opposite to each other. Core part  23  has both ends  23   a  and  23   b  opposite to each other. Core part  24  has both ends  24   a  and  24   b  opposite to each other. One end  21   a  of both ends  21   a  and  21   b  of core part  21  is connected to one end  23   b  of both ends  23   a  and  23   b  of core part  23 . Another end  23   b  of both ends  23   a  and  23   b  of core part  23  is connected to one end  22   a  of both ends  22   a  and  22   b  of core part  22 . Another end  22   b  of both ends  22   a  and  22   b  of core part  22  is connected to one end  24   a  of both ends  24   a  and  24   b  of core part  24 . Another end  24   b  of both ends  24   a  and  24   b  of core part  24  is connected to another end  21   b  of both ends  21   a  and  21   b  of core part  21 . 
     Coil  30  is made of a conductor. Coil  30  is wound around core  20 . Coil  30  includes coil part  31  and coil part  32 . Coil part  31  is electrically connected to coil part  32 . Coil part  31  is wound around a part of core part  21 . Coil part  32  is wound around a part of core part  22 . In accordance with Embodiment 1, coil  30  is made of a copper wire having a rectangular cross section, but may not necessarily have such a cross section. 
     In  FIGS. 1 to 5 , an X axis, a Y axis, and a Z axis perpendicular to each other are defined. Magnetic fluxes M 1  and M 2  generated by coil part  31  and coil part  32  pass through core  20  in the same direction. For example, as shown in  FIG. 1 , at a moment when magnetic flux M 1  generated by coil part  31  passes through core part  21  in a positive direction of the Y axis, through core part  22  in a negative direction of the Y axis, through core part  23  in a positive direction of the X axis, and through core part  24  in a negative direction of the X axis, magnetic flux M 2  generated by coil part  32  passes through core parts  21  to  24  in the same directions as magnetic flux M 1  generated by coil part  31 . Magnetic fluxes M 1  and M 2  are added to form magnetic flux M 3  passing through each part of core  20 . 
       FIG. 2  shows length L 1  of core part  21  in a direction in which magnetic flux M 3  passes, length L 2  of core part  22  in a direction in which magnetic flux M 3  passes, length L 3  of core part  23  in a direction in which magnetic flux M 3  passes, and length L 4  of core part  24  in a direction in which magnetic flux M 3  passes. Length L 1  of core part  21  is the mean value of outer length L 1a  of core part  21  and inner length L 1b  of core part  21 . Similarly, length L 2  of core part  22  is the mean value of outer length L 2a  of core part  22  and inner length L 2b  of core part  22 . Length L 3  of core part  23  is the mean value of outer length L 3a  of core part  23  and inner L 3b  of core part  23 . Length L 4  of core part  24  is the mean value of inner length L 4a  of core part  24  and inner length L 4b  of core part  24 . In accordance with Embodiment 1, lengths L 1  to L 4  satisfy relations: L 1 =L 2 ; and L 3 =L 4 . 
     As shown in  FIG. 3 , core  20  is partitioned into four parts: winding part  25 , winding part  26 , non-winding part  27 , and non-winding part  28 . Winding part  25  is a region of core part  21  around which coil part  31  is wound. Winding part  26  is a region of core part  22  around which coil part  32  is wound. Non-winding part  27  is a region including core part  23 , a portion of core part  21  connected to core part  23  except for winding part  25 , and a portion of core part  22  connected to core part  23  except for winding part  26 . Non-winding part  28  includes core part  24 , a portion of core part  21  connected to core part  24  except for winding part  25 , and a portion of core part  22  connected to core part  24  except for winding part  26 . 
     Core part  21  includes winding part  25  around which coil part  31  is wound, region  61   a  extending from one end  21   a  of core part  21  to winding part  25 , and region  61   b  extending from another end  21   b  of core part  21  to winding part  25 . Coil part  31  is not wound around any of regions  61   a  and  61   b . Core part  22  includes winding part  26  around which coil part  32  is wound, region  62   a  extending from one end  22   a  of coil part  22  to winding part  26 , and region  62   b  extending from another end  22   b  of core part  22  to winding part  26 . Coil part  32  is not wound around any of regions  62   a  and  62   b . Core part  23 , region  61   a  of core part  21 , and region  62   a  of core part  22  constitute non-winding part  27 . Core part  24 , region  61   b  of core part  21 , and region  62   b  of core part  22  constitute non-winding part  28 . 
     Core  20  has an annular shape. In accordance with Embodiment 1, core  20  has a rectangular annular shape. Winding part  26  is located away from winding part  25  along the annular shape. Non-winding part  27  extends from winding part  25  to winding part  26  along the annular shape. Non-winding part  28  extends from winding part  25  to winding part  26  along the annular shape, and is located opposite to non-winding part  27  with respect to winding parts  25  and  26 . 
     Winding part  25  has length A 1  in a direction of magnetic flux M 3  passing through winding part  25 . Winding part  26  has length A 2  in a direction of magnetic flux M 3  passing through winding part  26 . Non-winding part  27  has length B 1  along magnetic flux M 3  that passes through non-winding part  27 . Non-winding part  28  has length B 2  along magnetic flux M 3  that passes through non-winding part  28 . In the embodiment, winding part  25  is located at the center of core part  21  in the length direction, and winding part  26  is at the center of core part  22  in the length direction. Accordingly, the following relations are satisfied. 
         B   1   =L   3 +( L   1   −A   1 )/2+( L   2   −A   2 )/2 
         B   2   =L   4 +( L   1   −A   1 )/2+( L   2   −A   2 )/2 
     Since L 1 =L 2 , L 3 =L 4 , and A 1 =A 2  in accordance with the embodiment, the following relation is also satisfied. 
     
       
      
       B 
       1 
       =L 
       3 
       +L 
       1 
       −A 
       1 
       =L 
       4 
       +L 
       2 
       −A 
       2 
       =B 
       2  
      
     
     The rectangular annular shape of core  20  includes a pair of opposite sides  71  and  72 , and a pair of opposite sides  73  and  74 . Each of core parts  21  to  24  linearly extends to constitute respective one of four sides  71  to  74  of the rectangular annular shape (see  FIG. 3 ). Winding part  25  is provided at one opposite side  71  of the pair of opposite sides  71  and  72 . Winding part  26  is provided at another opposite side  72  of the pair of opposite sides  71  and  72 . Non-winding part  27  includes one opposite side  73  of the pair of opposite sides  73  and  74 . Non-winding part  28  includes another opposite side  74  of the pair of opposite sides  73  and  74 . 
     Reactors have been used in electric circuits to which a large current is applied. Upon having a large current flowing in, the reactor generates large heat. When the reactor generates such large heat, the reactor itself or electronic components disposed around the reactor are thermally affected. 
     Reactors have been demanded to have small sizes according to a demand to electronic components to have small sizes. However, in view of heat generation, a large reactor is preferable due to heat capacity and heat release area. A simple downsizing of the reactor may result in increasing the temperature of the reactor. 
     In reactor  10  in accordance with Embodiment 1, both of cross-sectional areas S 3  and S 4  of core parts  23  and  24  in a direction perpendicular to magnetic flux M 3  passing core parts  23  and  24  where coil  30  is not wound are smaller than both of cross-sectional areas S 1  and S 2  of core parts  21  and  22  in a direction perpendicular to magnetic flux M 3  passing core parts  21  and  22  around which coil  30  is wound. More specifically, cross-sectional areas S 1 , S 2 , S 3 , and S 4  satisfy relations: S 1 &gt;S 3 , S 1 &gt;S 4 , S 2 &gt;S 3 , and S 2 &gt;S 4  in reactor  10 . Even if cross-sectional areas S 3  and S 4  of core parts  23  and  24  where magnetic flux M 3  is relatively small are small, an influence of heat generation is small, hence providing the rector with a small size. The reduction of cross-sectional areas S 3  and S 4  of core parts  23  and  24  less influence on inductance than the reduction of cross-sectional areas S 1  and S 2  of core parts  21  and  22  where magnetic flux M 3  is relatively large. Reactor  10  thus suppresses the decrease of the inductance. 
     In reactor  10  in accordance with the embodiment, the sum of lengths A 1  and A 2  of winding parts  25  and  26  is shorter than the sum of lengths B 1  and B 2  of non-winding parts  27  and  28 . In other words, lengths A 1 , A 2 , B 1 , and B 2  satisfy a relation: A 1 +A 2 &lt;B 1 +B 2 . This relation reduces a loss due to insides of coil parts  31  and  32  being close to each other. 
     Magnetic flux M 3  is larger in winding parts  25  and  26  of core  20  that are regions around which coil parts  31  and  32  are wound than other regions. However, in reactor  10 , a distance between regions with large dimensional change is small to reduce a dimensional change due to magnetostriction. Accordingly, reactor  10  has less vibration and thus less vibration noise. 
       FIG. 6A  shows characteristics of reactor  10 . More specifically,  FIG. 6A  shows a relation between a loss of reactor  10  and ratio R AB  (R AB =(A 1 +A 2 )/(B 1 +B 2 )) which is the ratio of sum (A 1 +A 2 ) of length A 1  of winding part  25  and length A 2  of winding part  26  to sum (B 1 +B 2 ) of length B 1  of non-winding part  27  and length B 2  of non-winding part  28 . 
     With respect to circuitry efficiency, the loss of reactor  10  is preferably less than 420 W. When ratio R AB  exceeds 0.9, the coil loss becomes large. When ratio R AB  is less than 0.5, the coil loss can be suppressed, but a core loss becomes large. In addition, ratio R AB  equal to or smaller than 0.3 allows lengths of the winding parts to be extremely short, and prevents the coil from being wound easily. Accordingly, lengths A 1 , A 2 , B 1 , and B 2  preferably satisfy the relation: (B 1 +B 2 )×0.5&lt;A 1 +A 2 &lt;(B 1 +B 2 )×0.9 
     Cross-sectional areas S 1 , S 2 , S 3 , and S 4  of core parts  21 ,  22 ,  23 , and  24  preferably satisfy the following relations. 
         S   1 ×0.6&lt; S   3   &lt;S   1 ;
 
         S   1 ×0.6&lt; S   4   &lt;S   1 ;
 
         S   2 ×0.6&lt; S   3   &lt;S   2 ; and
 
         S   2 ×0.6&lt; S   4   &lt;S   2 .
 
     Reactor  10  can have a small size without causing magnetic saturation when cross-sectional areas S 1 , S 2 , S 3 , and S 4  satisfy the above relations. 
     In reactor  10  in accordance with the embodiment, length L 3  of core part  23  in a direction of magnetic flux M 3  passing through core part  23  and length L 4  of core part  24  in a direction of magnetic flux M 3  passing through core part  24  where coil  30  is not wound may be shorter than any of length L 1  of core part  21  in a direction of magnetic flux M 3  and length L 2  of core part  22  in a direction of magnetic flux M 3  where coil  30  is wound. In other words, reactor  10  may satisfy relations: L 1 &gt;L 3 ; L 1 &gt;L 4 ; L 2 &gt;L 3 ; and L 2 &gt;L 4 . The above relations of lengths L 1 , L 2 , L 3 , and L 4  provide reactor  10  with a small size. 
       FIG. 6B  shows a relation of a frequency and an alternating-current (AC) loss in a copper wire of the coil parts when ripple current is the same in samples with ratio R AB  of 0.6, 0.9, and 1.5.  FIG. 6B  shows AC losses in the copper wire at ratios R AB  and frequencies whereas the AC loss in copper wire is 100 when ratio R AB  is 0.6 and a frequency is 10 kHz.  FIG. 6B  also shows an increase rate of the AC loss at frequencies 50 kHz to 100 kHz with respect to the AC loss at frequency 10 kHz. 
     As shown in  FIG. 6B , the increase rate of the AC loss increases as the frequency increases. The increase rate is extremely high when ratio RAE becomes 1.5. In this regard, a significant effect is obtained at high frequencies when the following expression is satisfied: 
       ( B   1   +B   2 )×0.5&lt; A   1   +A   2 &lt;( B   1   +B   2 )×0.9.
 
     Exemplary Embodiment 2 
       FIG. 7  is a sectional view of reactor  10   a  in accordance with Exemplary Embodiment 2 for illustrating a cross section of reactor  10   a  parallel to the XY-plane. In  FIG. 7 , components identical to those of reactor  10  in accordance with Embodiment 1 shown in  FIGS. 1 to 5  are denoted by the same reference numerals. 
     In reactor  10   a  in accordance with Embodiment 2, gaps  41 ,  42 , and  43  are provided in core part  21  while gaps  51 ,  52 , and  53  are provided in core part  22 . 
     Gaps  41 ,  42 , and  43  are positioned in winding part  25 . Gaps  51 ,  52 , and  53  are positioned in winding part  25 . 
     Gaps  41  to  43  divide winding part  25  in a direction of magnetic flux M 3  passing through winding part  25 . Gaps  41  to  43  are arranged in a direction of magnetic flux M 3  passing through winding part  25 . Similarly, gaps  51  to  53  divide winding part  26  in a direction of magnetic flux M 3  passing through winding part  26 . Gaps  51  to  53  are arranged in a direction of magnetic flux M 3  passing through winding part  26 . 
     The gaps provided in winding parts  25  and  26  effectively causes a magnetic field applied to core  20  to be smaller than a magnetic field applied to the gaps, compared to the case of providing a gap in a portion of core  20  outside winding parts  25  and  26 . This configuration improves a direct-current (DC) superimposition characteristic while allowing the gaps to have small sizes. 
     INDUSTRIAL APPLICABILITY 
     A reactor according to the present invention is effectively applicable to passive elements utilizing an inductance. 
     REFERENCE MARKS IN THE DRAWINGS 
     
         
           10 ,  10   a  reactor 
           20  core 
           21  core part (first core part) 
           22  core part (second core part) 
           23  core part (third core part) 
           24  core part (fourth core part) 
           25  winding part (first winding part) 
           26  winding part (second winding part) 
           27  non-winding part (first non-winding part) 
           28  non-winding part (second non-winding part) 
           30  coil 
           31  coil part (first coil part) 
           32  coil part (second coil part) 
           41  gap (first gap) 
           42  gap (third gap) 
           43  gap 
           51  gap (second gap) 
           52  gap (fourth gap) 
           53  gap