Abstract:
An inductor includes common mode and differential mode flux paths. The inductor comprises a first core having a first segment, a second segment extending from the first segment and a first bridge segment extending from the second segment; a first wiring arrangement at least partially disposed around the first segment; a second core having a third segment, a fourth segment extending from the third segment and a second bridge segment extending from the fourth segment; and a second wiring arrangement at least partially disposed around the third segment; wherein the first segment, second segment, third segment and fourth segment cooperate to promote the common mode flux path, and the first bridge segment and the second bridge segment cooperate to promote the differential mode flux path.

Description:
REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Patent Application No. 61/046,939 filed on Apr. 22, 2008, and U.S. Provisional Patent Application No. 61/084,668 filed on Jul. 30, 2008. 
     
    
     BACKGROUND 
       [0002]    Three phase differential mode harmonics are typically filtered by placing three inductors in series with the line between the drive and motor. Common-mode harmonics are typically filtered by placing three parallel conductors on one magnetic core path. 
         [0003]    With relation to three phase AC motor controllers, particularly pulse width modulation (PWM) voltage source inverters (VSI), each phase of the three phases of a motor is connected to a VSI by a separate conductor. PWM VSI&#39;s operate by switching a DC voltage at a high frequency. All multiple conductor wire runs contain stray inductance and stray capacitance. This creates the possibility of a series resonant circuit in the motor cable system. The longer the motor cables, the lower the resonant frequency. The output of a PWM VSI Drive contains switching frequencies that can excite this natural resonance. If the switching frequency of the output power devices is high enough, and if the resonant frequency of the motor cable system is low enough, voltage spikes at the AC Motor terminals can easily reach double the DC bus voltage. These elevated voltages can cause premature failure of motors or damage the cables supplying the motor. 
       SUMMARY 
       [0004]    In one embodiment, the invention provides an inductor core structure that, when assembled, forms common mode and differential mode flux paths. 
         [0005]    In another embodiment, the invention provides a core assembly having an outer hexagonal shape. 
         [0006]    In another embodiment, the invention provides a core assembly having three inner-bridge structures. 
         [0007]    In another embodiment, the invention provides a core assembly having an outer shape (e.g., a hexagonal shape) to provide a common mode flux path. The core assembly further has three inner-bridge structures to provide respective differential mode flux paths. 
         [0008]    In another embodiment, the invention provides a core assembly having three core structures. Each core structure includes a leg and a bridge. The assembled core can be used in an inductor. The inductor includes three or six coils. Each coil is at least partially disposed around a leg. The inductor can reduce space and cost by integrating both the common mode and differential mode inductors onto one core assembly. 
         [0009]    In another embodiment, the invention provides a common mode and differential mode inductance assembly that includes three substantially identical core shapes that form a hexagonal outer surface shape. Three alternating legs of the hexagonal outside surface shape have a bridge that extends toward the center of the core. Each of the other three legs of the hexagonal shapes has a wiring arrangement comprised of one or two coils. The magnetic flux that flows through the core bridges is substantially differential mode flux. The magnetic flux that flows completely through the outer hexagonal shape is substantially common mode flux. 
         [0010]    In one embodiment, the invention provides an inductor including common mode and differential mode flux paths, the inductor comprising: a first core having a first segment, a second segment extending from the first segment and a first bridge segment extending from the second segment; a first wiring arrangement at least partially disposed around the first segment; a second core having a third segment, a fourth segment extending from the third segment and a second bridge segment extending from the fourth segment; and a second wiring arrangement at least partially disposed around the third segment; wherein the first segment, second segment, third segment and fourth segment cooperate to promote the common mode flux path, and the first bridge segment and the second bridge segment cooperate to promote the differential mode flux path. 
         [0011]    In another embodiment, the invention provides a method of manufacturing an inductor having common mode and differential flux paths, the method comprising: providing a first core having a first segment, a second segment extending from the first segment and a first bridge segment extending from the second segment; disposing a first wiring arrangement at least partially around the first segment; providing a second core having a third segment, a fourth segment extending from the third segment and a second bridge segment extending from the fourth segment; disposing a second wiring arrangement at least partially around the third segment; and placing the first core adjacent the second core such that the first segment, second segment, third segment and fourth segment cooperate to promote the common mode flux path and the first bridge segment and the second bridge segment cooperate to promote the differential mode flux path. 
         [0012]    In another embodiment, the invention provides an apparatus for essentially eliminating motor overvoltages due to resonances in the motor cable system. The apparatus includes a common mode/differential mode choke or inductor, three resistors and three capacitors. Each resistor is in series with a capacitor. Then each resistor and capacitor series is paralleled with each of the coils of the inductor. Each network of components is linked between the drive and the three supply lines to the motor. 
         [0013]    In another embodiment, the invention provides an apparatus for eliminating overvoltages due to resonances, the apparatus comprising: an inductor having common mode and differential mode flux paths, the inductor further including a first wiring arrangement and a second wiring arrangement; and a first circuit in parallel arrangement with the first wiring arrangement and a second circuit in parallel arrangement with the second wiring arrangement, each of the first circuit and the second circuit including a respective capacitive element and a respective resistive element in series arrangement. 
         [0014]    Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]      FIG. 1   a  schematically illustrates a first wiring arrangement of an inductor according to the invention. 
           [0016]      FIG. 1   b  schematically illustrates a second wiring arrangement of an inductor according to the invention. 
           [0017]      FIG. 1   c  schematically illustrates a third wiring arrangement of an inductor according to the invention. 
           [0018]      FIG. 2  is a top view of an inductor according to a first embodiment of the invention. 
           [0019]      FIG. 3  is a top view of a core element of the inductor in  FIG. 2 . 
           [0020]      FIG. 4  is a top view of an inductor according to a second embodiment of the invention. 
           [0021]      FIG. 5  is a top view of a core element of the inductor in  FIG. 4 . 
           [0022]      FIG. 6  is a top view of an inductor according to a third embodiment of the invention. 
           [0023]      FIG. 7  is a top view of a portion of a core element of the inductor in  FIG. 6 . 
           [0024]      FIG. 8  is a top view of an inductor according to a fourth embodiment of the invention. 
           [0025]      FIG. 9  is a top view of a core element of the inductor in  FIG. 8 . 
           [0026]      FIG. 10  is a top view of an inductor according to a fifth embodiment of the invention. 
           [0027]      FIG. 11  is a top view of a portion of a core element of the inductor in  FIG. 10 . 
           [0028]      FIG. 12  is a perspective view of an exemplary construction of the inductor in  FIG. 4 . 
           [0029]      FIG. 13  is a perspective view of a mounting plate of the inductor in  FIG. 12 . 
           [0030]      FIG. 14  is a perspective view of an exemplary construction of the inductor in  FIG. 10 . 
           [0031]      FIG. 15  is a perspective view of a mounting bracket of the inductor in  FIG. 14 . 
           [0032]      FIG. 16  is a perspective view of an exemplary construction of an inductor according to the invention. 
           [0033]      FIG. 17  is a perspective view of another exemplary construction of an inductor according to the invention. 
           [0034]      FIG. 18  is a perspective view of a cup of the exemplary construction in  FIG. 17 . 
           [0035]      FIG. 19  is a perspective view of a wiring arrangement of an inductor according to the invention. 
           [0036]      FIG. 20  is a detailed view of a core element of an inductor according to first embodiment of the invention. 
           [0037]      FIG. 21  is a top view of an exemplary construction of an inductor according to the invention. 
           [0038]      FIG. 22  is a detailed view of the exemplary construction in  FIG. 21 . 
           [0039]      FIG. 23  is a schematic view of a circuit incorporating an inductor according to the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0040]    Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof, as well as additional items. Unless specified or limited otherwise, the terms “mounted,” “connected,” “supported,” and “coupled” and variations thereof encompass both direct and indirect mountings, connections, supports, and couplings. Further, “connected” and “coupled” are not restricted to physical or mechanical connections or couplings. 
         [0041]    The entire contents of U.S. Provisional Patent Application No. 61/046,939, U.S. Provisional Patent Application No. 61/084,668 and U.S. Pat. No. 5,990,654 are fully incorporated herein by reference. 
         [0042]      FIGS. 2 ,  21  and  22  illustrate an inductor or filter  10  according to a first embodiment of the invention. The inductor  10  includes three core elements or structures  15 ,  20 ,  25 . Some skilled in the art may also refer to the structures  15 ,  20 ,  25  as, simply, cores. Each of the cores  15 ,  20 ,  25  is a unitary piece and is manufactured from a magnetic material such as powdered iron, molypermalloy, ferrite or sendust.  FIGS. 3 and 20  show more specifically the shape of a single core element  15 ,  20 ,  25 . 
         [0043]    In the illustrated construction of  FIGS. 2 ,  3 , and  20 - 22 , each core  15 ,  20 ,  25  includes a first segment or leg  30  and a second segment or leg  35  extending from one end of the first leg  30 . The first leg  30  and the second leg  35  define an angle of about 120 degrees therebetween. As illustrated, the legs  30  of each of the core structures  15 ,  20 ,  25  are utilized to support windings  40 ,  45 ,  50 , respectively. Further, in the construction illustrated in  FIG. 2 , the first leg  30  of each of the core structures  15 ,  20 ,  25  also supports a second set of windings  55 ,  60 ,  65 , respectively. The leg  30  can have a rectangular cross section, which allows coils (e.g., the wiring arrangement illustrated in  FIG. 19 ) to be wound on similar cross-section shaped bobbins to slide onto leg  30  of the corresponding core structure  15 ,  20 ,  25 . As illustrated in  FIG. 2 , the legs  30 ,  35  of the cores  15 ,  20 ,  25  form a common mode flux path  70 . 
         [0044]      FIGS. 1   a,    1   b  and  1   c  illustrate three wiring arrangements for inductors according to the invention. For ease of description, the numbers referenced in  FIGS. 1   a,    1   b  and  1   c  for describing the wiring arrangements correspond to the numbers of wiring arrangements in  FIGS. 2 ,  4 ,  6 ,  8 , and  10 . Particularly,  FIG. 1   c  illustrates an arrangement where each of the core structures (e.g., cores  15 ,  20 ,  25  in  FIG. 2 ) supports a single coil  40 ,  45 ,  50 .  FIGS. 1   a  and  1   b  illustrate arrangements where each of the core structures  15 ,  20 ,  25  supports two coils  40  and  55 ,  45  and  60 , and  50  and  65 .  FIG. 1   a  shows wiring arrangements where coils  40  and  55 ,  45  and  60 , or  50  and  65  on each core  15 ,  20 ,  25  have the same orientation for strengthening magnetic flux.  FIG. 1   b  shows wiring arrangements where coils  40  and  55 ,  45  and  60 , or  50  and  65  on each core  15 ,  20 ,  25  of have opposite orientations for weakening flux, as further explained below. It is to be understood that the arrangements illustrated in  FIGS. 1   a,    1   b  and  1   c  are applicable to all inductors described in this application and to other inductors incorporating the invention but not specifically described herein. 
         [0045]    In the illustrated construction, each core  15 ,  20 ,  25  also includes a radially oriented segment or core bridge  75 . Accordingly, the inductor  10  includes a total of three core bridges  75 . The three core bridges  75  extend toward the center of the inductor  10  and each core bridge  75  extends from one corresponding leg  35  of cores  15 ,  20 ,  25 . With specific reference to  FIGS. 3 and 20 , the core bridge  75  extends substantially perpendicular from the leg  35  and the width of the bridge  75  is relatively smaller than the width of each of the legs  30 ,  35 . The cores  15 ,  20 ,  25  are manufactured to form a radius  80  between the walls of the bridge  75  and leg  35 . The radius  80  between the core bridges  75  and legs  35  provide additional mechanical support between the core legs  35  and bridges  75 . The core bridges  75  in cooperation with corresponding legs  30 ,  35  form three differential mode flux paths  85 ,  90 ,  95 . 
         [0046]    In the illustrated construction, the end of each of the core bridges  75  forms a point end  100  (with respect to the top view in  FIG. 3 , for example) defining two end walls  105 A,  105 B. End walls  105 A,  105 B of each core bridge  75  are adjacent to and substantially parallel with other end walls  105 A,  105 B of the core bridges  75 . The point ends  100  distribute the flux evenly along the ends of the core bridges  75 . The arrangement of the core bridges  75  of the inductor  10 , and particularly of the end walls  105 A,  105 B, can help reduce localized saturation of the cores  15 ,  20 ,  25 . In the illustrated construction, each end wall  105 A,  105 B and the corresponding adjacent end wall  105 A,  105 B of adjacent core bridges  75  form a space of non-magnetic material  110 ,  115 ,  120  substantially at the center of the inductor  10  and between each of the core bridges  75 . The material is typically air or a potting material. 
         [0047]    With reference to  FIG. 2 , the inductor  10  also includes three exterior gaps  125  between end portions of adjacent legs  30 ,  35  of core structures  15 ,  20 ,  25 . The reluctance of the common mode flux path  70  for a given core shape is controlled by the permeability of the material. Since there is, typically, a limited number of standard material permeabilities used to design the core structure, the resulting size may not be optimal. The exterior gaps  125  of the illustrated constructions allow for the control of the reluctance of the common mode flux path  70 . Particularly, adjusting the size of the external gap  125  and selecting the material of the core  15 ,  20 ,  25  allow adjusting the core permeability. For example, the further the core structures  15 ,  20 ,  25  are spaced apart due to the thickness of external spacers  130  filling or forming the gaps  125 , the lower the common mode inductance is. 
         [0048]    The flexibility in designing cores  15 ,  20 ,  25 , based on selecting core material and/or adjusting the size of gaps  125 , can allow producing an inductor (e.g., inductor  10 ) of relatively smaller size. In  FIG. 2 , the common mode inductance is illustrated as the common flux path  70 . The external spacers  130  forming the gaps  125  can be constructed from nonmagnetic material such as Glastic or Nomex materials. 
         [0049]    The amount of differential mode inductance (illustrated in  FIG. 2  as the differential mode flux paths  85 ,  90 ,  95 ), as compared to the common mode inductance, can be adjusted during the design phase of the inductor  10  by adjusting and selectively changing the amount of space  110 ,  115 ,  120  in the center of the inductor  10  between the core bridges  75  and/or by changing the width of the core bridges  75 . For example, cores (e.g.,  15 ,  20 ,  25 ) that define smaller core spaces  110 ,  115 ,  120  generally have proportionately more differential mode inductance. In addition, cores that have wider core bridges  75  also have more differential mode inductance. 
         [0050]    Another method for adjusting common mode inductance is to vary the wiring arrangement. For example, the inductor illustrated in  FIG. 2  includes two coils (e.g., coils  40 ,  55 ) mounted on each core  15 ,  20 ,  25 . To increase common mode inductance, the wiring arrangements on each core  15 ,  20 ,  25  are arranged with the polarities as shown in  FIG. 1   a.  In other words, the coils on each core  15 ,  20 ,  25  are arranged with the same polarity. Further, the greater the amount of turns in coils  55 ,  60 ,  65 , as compared to coils  40 ,  45 ,  50 , increases the common mode inductance. On the contrary, to decrease common mode inductance, the wiring arrangements on each core  15 ,  20 ,  25  are arranged with polarities as shown in  FIG. 1   b.  The greater the amount of turns in coils  55 ,  60 ,  65 , as compared to coils  40 ,  45 ,  50 , decreases the common mode inductance. 
         [0051]      FIGS. 4 and 5  illustrate an inductor or filter  200  according to a second embodiment of the invention. The inductor  200  includes many features in common with other inductors described in this application and common elements have been given the same reference numerals. Accordingly, reference is made to other inductors described in this application for additional features and alternatives to the inductor  200  and the following description makes reference to the differences between inductor  200  and other inductors described in this application. 
         [0052]    In the illustrated construction, the use of the exterior core gaps  125 , as described with respect to the inductor  10  in  FIG. 2 , are typically not used in the construction of inductor  200  of  FIG. 4 . Particularly, each core  15 ,  20 ,  25  includes attachment assemblies for coupling the cores to one another. As illustrated in  FIG. 5 , leg  35  of each core  15 ,  20 ,  25  has a notch  205  and leg  30  includes a protrusion  210 . The notch  205  is designed to receive a corresponding protrusion  210  of the adjacent leg  30 . The notches  205  and protrusions  210  assist in positioning of the core pieces  15 ,  20 ,  25  with respect to one another as shown in FIG.  4 . As a result, assembly time is improved with respect to other inductor devices, and the variations of core positions that can affect inductance values are reduced. Other constructions of the inductor  200  can include a different number of notches  205  and protrusions  210  for assembling the inductor  200 . Further, other attachment assemblies not specifically described herein fall within the scope of the invention. 
         [0053]      FIGS. 6 and 7  illustrate an inductor or filter  300  according to a third embodiment of the invention. The inductor  300  includes many features in common with other inductors described in this application and common elements have been given the same reference numerals. Accordingly, reference is made to other inductors described in this application for additional features and alternatives to the inductor  300 , and the following description makes reference to the differences between inductor  300  and other inductors described in this application. 
         [0054]    In the illustrated construction, each of the cores  15 ,  20 ,  50  of inductor  300  is constructed from a number of stacked laminations  305 . The laminations  305  can be made from stacked lamination material, such as silicon steel or nickel iron. Each of the laminations  305  also includes a hole or aperture  310  placed into the lamination  305  for a holding mechanism (e.g., screw, bolt, nail) to support the lamination stack together. The location of the hole  310  is “under” the core bridges  75  and near the outer (or peripheral) edge of the core leg  35 . That is, the hole  310  is formed in alignment with respect to the longitudinal direction of the core bridge  75  and adjacent the outer edge of the core  15 ,  20 ,  25 . 
         [0055]    The hole  310  is formed in the illustrated location because that location of the core has a lower flux density than other portions of the core as measured or determined prior to forming the hole  310  in the stack of laminations  305 . In other words, as determined from a core without the hole  310  therein. As a consequence, adding or forming the hole  310 , as illustrated in  FIG. 7 , increases the flux density around the hole  310 . However, the impact of forming the hole  310 , as illustrated, has limited negative or detrimental impact in the operation of the inductor  300 . In addition, the radius  80  between the core bridges  75  and legs  35  that provides additional mechanical support between the core legs  35  and bridges  75  ( FIG. 2 ) is not required (even though it may be present) in the construction of the cores  15 ,  20 ,  25  of inductor  300 . This particular feature is not necessary because the metallic laminations  305  have enough strength without the radius  80  as shown in  FIG. 3 . 
         [0056]      FIGS. 8 and 9  illustrate an inductor or filter  400  according to a fourth embodiment of the invention. The inductor  400  includes many features in common with other inductors described in this application and common elements have been given the same reference numerals. Accordingly, reference is made to other inductors described in this application for additional features and alternatives to the inductor  400  and the following description makes reference to the differences between inductor  400  and other inductors described in this application. 
         [0057]    In the illustrated construction, the inductor  400  as shown in  FIG. 8  includes much of the same characteristics as the inductor  10  as shown in  FIG. 2  with the difference that each of the exterior gaps  125  is located inside the wiring arrangements  40  and  55 ,  45  and  60 , and  50  and  65 . Placing the wire arrangements with respect to the exterior gaps  125 , as shown in  FIG. 8 , restricts movement of the cores  15 ,  20 ,  25  and exterior gaps  125  in two directions (radially and circularly), thereby making the inductor  400  more consistent and easier to construct. This construction results in the gaps  125  being less accessible during assembly. However, the exterior gap thickness may still be adjusted during assembly of the inductor  400  to adjust the inductance value. 
         [0058]    With specific reference to  FIG. 9 , the core  15 ,  20 ,  25  includes a substantially symmetrical construction with respect to a longitudinal axis of the core bridge  75 . Particularly, the core  15 ,  20 ,  25  includes a center piece or segment  405  formed substantially perpendicular to the core bridge  75 . First and second outer segments or legs  410 ,  415  each extends from the center piece  405  at an angle with respect to the center piece  405 . It is to be understood that other configurations of the core  15 ,  20 ,  25  also fall within the scope of the invention. 
         [0059]      FIGS. 10 and 11  illustrate an inductor  500  according to a fifth embodiment of the invention. The inductor  500  includes many features in common with other inductors described in this application, and common elements have been given the same reference numerals. Accordingly, reference is made to other inductors described in this application for additional features and alternatives to the inductor  500  and the following description makes reference to the differences between inductor  500  and other inductors described in this application. 
         [0060]    The illustrated construction of the inductor  500  includes much of the same characteristics as the construction of inductor  400  shown in  FIG. 8 , with the difference that the core structure  15 ,  20 ,  25  is constructed from stacked lamination material such as silicon steel or nickel iron. Particularly, lamination plates  505 , such as the one illustrated in  FIG. 11 , include a similar structure as the core  15 ,  20 ,  25  illustrated in  FIG. 9  and also include holes or apertures  510  similar to the holes  310  discussed with respect to  FIGS. 6 and 7 . Lamination plates  505  also include a center piece or segment  515  and first and second outer segments or legs  520 ,  525  extending from then center piece  515 . Laminations  505  can include other configurations that also fall within the scope of the invention. 
         [0061]    Windings or wiring structures  40 ,  45 ,  50  and windings or wiring structures  55 ,  60 ,  65 , if included, of the exemplary constructions shown in  FIGS. 12 ,  14 ,  16 ,  17  can be wound with magnet wire, Litz wire, lead wire, or copper foil. For example, the construction of each wiring structure, such as the wiring structures illustrated in  FIG. 17 , can includes a bobbin  530 ,  535 ,  540  generally formed from rynite or glass-filled nylon. The coils may be terminated with terminals, leads, or crimps.  FIG. 19  illustrates a bobbin  550  with coils as illustrated in  FIGS. 1   a  and  1   b.  The bobbin  550  shown in  FIG. 19  has a dividing flange  555  to control the amount of mutual inductance between coils due to proximity with respect to each other. The bobbins  530 ,  535 ,  540  can include an integral termination. Other methods and techniques for winding and terminating coils are known in the art, and consequently, the bobbin type construction needs not be discussed further herein. 
         [0062]      FIGS. 12 and 13  illustrate an exemplary construction of an inductor or filter  600  according to an embodiment of the invention. The inductor  600  includes many features in common with other inductors described in this application and common elements have been given the same reference numerals. Accordingly, reference is made to other inductors described in this application for additional features and alternatives to the inductor  600  and the following description makes reference to the differences between inductor  600  and other inductors described in this application. 
         [0063]      FIG. 12  illustrates an exemplary construction of an inductor  600  according to the invention. Particularly,  FIG. 12  shows a mechanical construction that can be used to make an inductor as shown in the embodiments described with respect to  FIGS. 2 ,  4  and  8 . The inductor  600  includes a metal banding strap  605 , typically made from steel or stainless steel. The strap  605  is placed around the outside of the core pieces  15 ,  20 ,  25  and through a mounting bracket  610 . The strap  605  also includes a banding clip  615  for securing the strap  605  around the cores  15 ,  20 ,  25 .  FIG. 13  illustrates the mounting bracket  610  of the inductor  600  for supporting the cores  15 ,  20 ,  25 . The mounting bracket  610  includes two openings  625 ,  630  for the strap  605  to go through. The mounting bracket  610  also includes holes  640 ,  645  for receiving attachment mechanisms and mounting the inductor  600  at a desired location. In other constructions, the mounting bracket  610  does not include holes  640 ,  645  and other means for coupling the inductor  600  are utilized, such as captive fasteners (e.g., clamps). In the illustrated construction, the bracket  610  provides a separation between the cores  15 ,  20 ,  25  and the surface (not shown) where the inductor is mounted to. However, other configurations of the bracket  610  fall within the scope of the invention. 
         [0064]      FIGS. 14 and 15  illustrate another exemplary construction of an inductor or filter  700  according to an embodiment of the invention. The inductor  700  includes many features in common with other inductors described in this application and common elements have been given the same reference numerals. Accordingly, reference is made to other inductors described in this application for additional features and alternatives to the inductor  700  and the following description makes reference to the differences between inductor  700  and other inductors described in this application. 
         [0065]      FIG. 14  illustrates an exemplary construction of the inductor  700  according to the invention. Particularly,  FIG. 14  shows a mechanical construction that can be used to make an inductor as shown in the embodiments described with respect to  FIGS. 6 and 10 . In the illustrated construction, three screws  705  are placed through core holes (i.e., holes formed by apertures  510  of laminations  505  in  FIG. 11 ) to attach cores  15 ,  20 ,  25  to a metal mounting bracket  710  of the inductor  700 .  FIG. 15  shows a more detailed view of the mounting bracket  710  of inductor  700 . The bracket  710  includes three legs  715  with receiving apertures  720  for receiving screws  705 . In the illustrated construction, screws  705  can be retained with the bracket  710 , thus securing cores  15 ,  20 ,  25 , with respective nuts. Other constructions of the inductor  700  can include captive fasteners to secure the cores  15 ,  20 ,  25  to the bracket  710 . The bracket  710  further includes attachment apertures  725  for receiving coupling mechanisms (e.g., screws, bolts, nails) and coupling the inductor  700  to a desired location. In the illustrated construction, the bracket  710  provides a separation between the cores  15 ,  20 ,  25  and the surface (not shown) where the inductor is mounted to. However, other configurations of the bracket  710  fall within the scope of the invention. 
         [0066]      FIG. 16  illustrates another exemplary construction of an inductor or filter  800  according to an embodiment of the invention. The inductor  800  includes many features in common with other inductors described in this application and common elements have been given the same reference numerals. Accordingly, reference is made to other inductors described in this application for additional features and alternatives to the inductor  800  and the following description makes reference to the differences between inductor  800  and other inductors described in this application. 
         [0067]    In the illustrated construction, insulated cables  40 ,  45 ,  50  are each wound around leg  30  of a corresponding core section  15 ,  20 ,  25 . During operation of the inductor  800 , current from each phase of a three phase power system would be applied to leads  805 ,  810 ,  815  of each corresponding winding  40 ,  45 ,  50 . Inductor  800  also includes a mounting bracket  820  similar to bracket  610  in  FIG. 13  and a branding strap  825  similar to strap  605  in  FIG. 12 . For assembly purposes, the inductor  800  may be provided to the end customer as core assembly including cores  15 ,  20 ,  25  coupled as described above but without windings  40 ,  45 ,  50 . The customer then could wind the required amount of turns around the core  15 ,  20 ,  25 . Particularly, the customer can use insulated cable or wire in place of bobbins (e.g., bobbin  550  in  FIG. 19 ) for other core assemblies or constructions. 
         [0068]      FIGS. 17 and 18  illustrate another exemplary construction of an inductor or filter  900  according to an embodiment of the invention. The inductor  900  includes many features in common with other inductors described in this application and common elements have been given the same reference numerals. Accordingly, reference is made to other inductors described in this application for additional features and alternatives to the inductor  900  and the following description makes reference to the differences between inductor  900  and other inductors described in this application. 
         [0069]    In the illustrated construction, cores  15 ,  20 ,  25 , bobbins  530 ,  535 ,  540 , and windings  40 ,  45 ,  50  are placed into a cup  905 . The cup  905 , which is also shown in  FIG. 18 , can be filled with an electrical potting compound, such as epoxy, to secure the cores  15 ,  20 ,  25 , bobbins  530 ,  535 ,  540 , and windings  40 ,  45 ,  50  into place. The terminals  930 ,  931 ,  932 ,  933 ,  934 ,  935  can be self leads from the windings  40 ,  45 ,  50  or can be constructed from wire of another gauge. The leads from the coils can be soldered into place. As illustrated in  FIG. 18 , the cup  905  includes six holes or apertures  911 ,  912 ,  913 ,  914 ,  915 ,  916  for receiving terminals  930 ,  931 ,  932 ,  933 ,  934 ,  935  therethrough. Also, the cup  905  defines an irregular hexagonal shape. However, other forms or configurations of the cup  905  fall within the scope of the invention. 
         [0070]      FIG. 23  is a schematic representation of an apparatus or circuit  1000  including an inductor or filter  1100  connected between a drive circuit  1105  and a cable system that is in turn connected to a motor  1115 . It is to be understood that the inductor  1100  can include any combination of the characteristics and limitations of an inductor as described in the present application. Accordingly, no further description of the inductor  1100  is necessary. The inductor  1100  includes three wiring arrangements  1130 A,  1130 B,  1130 C electrically connecting the drive  1105  to cable system  1110  that leads to the motor  1115 . 
         [0071]    In addition, the circuit  1000  includes three circuits  1135 A,  1135 B,  1135 C also connecting the drive  1105  to the cable system  1110 . Each circuit  1135 A,  1135 B,  1135 C is in parallel arrangement with one corresponding wiring arrangement  1130 A,  1130 B,  1130 C. Each circuit  1135 A,  1135 B,  1135 C also includes a capacitive element  1120 A,  1120 B,  1120 C and a resistive element  1125 A,  1125 B,  1125 C. It is to be understood that although only one capacitor and one resistor are shown in  FIG. 23  for each circuit  1135 A,  1135 B,  1135 C, the invention encompasses other suitable combinations of capacitive and resistive elements or other elements with capacitive and resistive properties. 
         [0072]    A first improvement of the circuit  1000  over other circuits, such as the circuit illustrated in  FIG. 4  of U.S. Pat. No. 5,990,654, is that inductor  1100  incorporates the characteristics of previously separated or individual common mode inductors and differential mode inductors. This allows the reduction of size and cost of the components (e.g., magnetic components) in the filter  1100  and circuit  1000 . 
         [0073]    A second improvement of the circuit  1000  over other circuits, such as the circuit illustrated in  FIG. 4  of U.S. Pat. No. 5,990,654, is the implementation of additional capacitive elements  1120 A,  1120 B,  1120 C, which can be combined with resistive elements  1125 A,  1125 B,  1125 C. More specifically, the teachings of U.S. Pat. No. 5,990,654 require that “[w]ith respect to carrier frequency range fc, it is desirable if the R-L impedance combination operates as a pure inductor with a 90 phase angle and zero impedance at carrier frequencies fc so as to facilitate complete current flow through the inductor, keep watts loss in the resistor to a minimum and so as to minimize ripple current.” 
         [0074]    In contrast with the teachings of U.S. Pat. No. 5,990,654, it is believed that capacitive elements  1120 A,  1120 B,  1120 C of circuit  1000  having a value between about 0.100 uF to 0.500 uF offer high impedance at the carrier frequencies. This substantially eliminates any current at carrier frequencies through the resistive elements  1125 A,  1125 B,  1125 C. As a consequence, the losses in the resistive elements  1125 A,  1125 B,  1125 C are reduced, which also results in the reduction of size and/or cost of the circuit  1000  with respect to other circuits. Troublesome frequencies, such as the ones near the resonant frequency of the cable  1110 , are mostly unaffected by the low impedance of the capacitive elements  1120 A,  1120 B,  1120 C. It is to be understood that a person of ordinary skill in the art will readily recognize other advantages and improvements presented by circuit  1000  but not specifically discussed herein. 
         [0075]    Various features and advantages of the invention are set forth in the following claims.