Abstract:
A method for use in reducing an inductance of a circuit including a commutation loop defined at least in part by a source conductor and a return conductor between a first component and a second component is described. The method includes disposing a conductive inductance reducer within the commutation loop. The conductive inductance reducer includes an electrically conductive material and an insulator.

Description:
BACKGROUND 
       [0001]    This description relates to loop inductance in electrical circuits, and more particularly, to systems and methods for reducing loop inductance in electrical circuits. 
         [0002]    Known electrical circuits often include sections in which a current passes from a first component to a second component and returns to the first component. The paths between the first and second component form a current loop.  FIG. 1  is a diagram of a portion of an electrical circuit  10  including a current loop  15 . The electrical circuit  10  is part of a power converter, e.g., an inverter or a multi-level converter. Current loop  15  includes a source conductor  20  and a return conductor  25 . Circuit  10  includes phase leg  30  of a power converter coupled to a direct current DC link capacitor  35  by source conductor  20  and return conductor  25 . Current loop  15  defines a loop area  40  within current loop  15 . During operation of circuit  10 , current passes around current loop  15 , for example clockwise around loop  15 . Current loop  15  has a parasitic inductance, sometimes referred to as a loop inductance, that depends on the shape and size of current loop  15 . The inductance of current loop  15  is proportional to the area of loop area  40 . Unintended loop inductance may cause malfunctioning in electrical circuits. In general circuit designers identify sources of loop inductance, calculate the inductance, and factor the loop inductance into the circuit design to permit the circuit to operate as intended. Loop inductance may result in relatively large voltage overshoot and ringing in switching circuits, such as circuit  10 . 
         [0003]    Some known systems attempt to reduce the inductance of current loops by placing source and return conductors closer together, thereby reducing the area of the current loop. In high voltage circuits, however, source and return conductors located close together may be susceptible to arcing and insulation breakdown. Other known systems attempt to reduce loop inductance by using wide conductive plates separated by insulation, rather than wires, for the source and return conductors. Electrical circuits using wide plates instead of wires can be more expensive, more difficult to construct, and larger than wire based systems. Another known method to reduce loop inductance is to use a twisted pair of wires for the source and return conductors, but this can be difficult to construct for high voltage and high current use. 
       BRIEF DESCRIPTION 
       [0004]    In one aspect, a method for use in reducing an inductance of a circuit is provided. The circuit includes a commutation loop defined at least in part by a source conductor and a return conductor between a first component and a second component. The method includes disposing a conductive inductance reducer within the commutation loop. The conductive inductance reducer includes an electrically conductive material and an insulator. 
         [0005]    In another aspect, a circuit is provided. The circuit includes a first component, a second component, a source conductor coupled between the first and second components, and a return conductor coupled between the first and second components. A commutation loop having an inductance is defined, at least in part, by the source and return conductors. The circuit includes a conductive inductance reducer disposed in the commutation loop to reduce the inductance of the commutation loop. 
         [0006]    In a further aspect, a power converter is provided. The power converter includes a phase leg, a direct current (DC) link, a source conductor coupled between the phase leg and the DC link, a return conductor coupled between the phase leg and the DC link. A commutation loop having an inductance is defined, at least in part, by the source and return conductors. A conductive inductance reducer is disposed in the commutation loop to reduce the inductance of the commutation loop. 
     
    
     
       DRAWINGS 
         [0007]    These and other features, aspects, and advantages of the present disclosure will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein: 
           [0008]      FIG. 1  is an exemplary known converter phase leg connected to a direct current (DC) link; 
           [0009]      FIG. 2  is a block diagram of an exemplary system including an inductance reducer disposed in a commutation loop between a source and a load; 
           [0010]      FIG. 3  is an exemplary system including a conductive loop inductance reducer disposed within a commutation loop of a converter phase leg connected to a DC link; and 
           [0011]      FIG. 4  is an exemplary system including a conductive plate inductance reducer disposed over commutation loop of a converter phase leg connected to a DC link. 
       
    
    
       [0012]    Unless otherwise indicated, the drawings provided herein are meant to illustrate features of embodiments of the disclosure. These features are believed to be applicable in a wide variety of systems comprising one or more embodiments of the disclosure. As such, the drawings are not meant to include all conventional features known by those of ordinary skill in the art to be required for the practice of the embodiments disclosed herein. 
       DETAILED DESCRIPTION 
       [0013]    In the following specification and the claims, reference will be made to a number of terms, which shall be defined to have the following meanings. 
         [0014]    The singular forms “a”, “an”, and “the” include plural references unless the context clearly dictates otherwise. 
         [0015]    “Optional” or “optionally” means that the subsequently described event or circumstance may or may not occur, and that the description includes instances where the event occurs and instances where it does not. 
         [0016]    Approximating language, as used herein throughout the specification and claims, may be applied to modify any quantitative representation that could permissibly vary without resulting in a change in the basic function to which it is related. Accordingly, a value modified by a term or terms, such as “about”, “approximately”, and “substantially”, are not to be limited to the precise value specified. In at least some instances, the approximating language may correspond to the precision of an instrument for measuring the value. Here and throughout the specification and claims, range limitations may be combined and/or interchanged, such ranges are identified and include all the sub-ranges contained therein unless context or language indicates otherwise. 
         [0017]    Embodiments of the present disclosure relate to loop inductance in electrical circuits. More particularly, the exemplary embodiments relate to systems and methods for reducing loop inductance in electrical circuits. Exemplary inductance reducers are positioned within or adjacent to an inductive loop to reduce the inductance of the loop. 
         [0018]      FIG. 2  is a block diagram of an exemplary system  100  including a conductive inductance reducer  102  disposed proximate a commutation loop  104  between a source  106  and a load  108 . Conductive inductance reducer  102  is disposed in a sufficiently close relationship with commutation loop  104  to be electromagnetically coupled with commutation loop  104 . In the exemplary embodiment, conductive inductance reducer  102  is disposed within commutation loop  104 . In other embodiments, conductive inductance reducer  102  extends outside of commutation loop  104 . In some embodiments, conductive inductance reducer  102  is disposed near commutation loop  104 , such as adjacent to or overlying commutation loop  104 . 
         [0019]    Conductive inductance reducer  102  is a passive component that interacts with the magnetic fields produced by electric current traveling around commutation loop  104  to reduce the inductance of commutation loop  104 . More specifically, conductive inductance reducer  102  substantially cancels out the magnetic fields generated by current through commutation loop  104  and passing through conductive inductance reducer  102 . Thus, the magnetic fields produced within commutation loop  104  are reduced by an amount substantially proportional to the percentage of commutation loop  104  occupied by conductive inductance reducer  102 . 
         [0020]      FIG. 3  is an exemplary system  300  including a commutation loop  302  between a converter phase leg  304  and a DC link  306 . Exemplary system  300  is a portion of a power converter, such as, without limitation, an inverter. In the exemplary embodiment, inductance reducer  102  is a conductive loop inductance reducer  308  disposed within commutation loop  302 . Conductive loop inductance reducer  308  is configured (e.g., sized and positioned) to surround substantially all of the area of commutation loop  302  and to be electromagnetically coupled to commutation loop  302  to reduce the inductance of commutation loop  302 . In other embodiments, conductive loop inductance reducer  308  overlaps or extends beyond some or all of commutation loop  302 . 
         [0021]    Conductive loop inductance reducer  308  is a loop of an electrical conductor. In other implementations, conductive loop inductance reducer  308  includes more than one loop of electrical conductor connected in series, parallel, or series and parallel. In the exemplary embodiment, conductive loop inductance reducer  308  is a loop of insulated wire. In other embodiments, conductive loop inductance reducer  308  is a conductive trace on a circuit board, conductive rods, or any other electrically conductive loop suitable for use as a conductive loop inductance reducer. In the exemplary embodiment, conductive loop inductance reducer  308  is made of copper. In other embodiments, conductive loop inductance reducer  308  includes any other suitable conductive material or combination of materials. 
         [0022]    In some embodiments, conductive loop inductance reducer  308  is configured to include a resistive component  310 . Resistive component  310  may be a discrete resistor coupled in series with the loop of conductive loop inductance reducer  308  or may be an integral characteristic of conductive loop inductance reducer  308  by appropriate selection of conductor size, length, and the like. Resistive component  310  in conductive loop inductance reducer  308  provides some additional damping during switching transitions to limit voltage overshoot and ringing. 
         [0023]    In the exemplary embodiment, conductive loop inductance reducer  308  is galvanically isolated. In other embodiments, conductive loop inductance reducer  308  is galvanically connected to ground, a node of the circuit in which it is located, or any other suitable reference. 
         [0024]      FIG. 4  is an exemplary system  400  similar to system  300  and including commutation loop  302  between converter phase leg  304  and DC link  306 . Exemplary system  400  is a portion of a power converter, such as, without limitation, an inverter. In exemplary system  400 , inductance reducer  102  is a conductive plate inductance reducer  402  disposed proximate commutation loop  302 . Conductive plate inductance reducer  402  is disposed adjacent to commutation loop  302  and electromagnetically coupled to commutation loop  302  to reduce the inductance of commutation loop  302 . Conductive plate inductance reducer  402  is configured (e.g., sized and positioned) to overlie substantially all of commutation loop  302  and to extend beyond at least part of commutation loop  302 . In other embodiments, conductive plate inductance reducer  402  is configured to lie completely within or overlap portions of commutation loop  302 . 
         [0025]    Conductive plate inductance reducer  402  is a plate of an electrically conductive material. In other implementations, conductive plate inductance reducer  402  includes more than one plate connected in series, parallel, or series and parallel. In some embodiments, conductive plate inductance reducer  402  is a conductive trace/area on a circuit board. In the exemplary embodiment, conductive plate inductance reducer  402  is made of copper. In other embodiments, conductive plate inductance reducer  402  includes any other suitable conductive material or combination of materials. 
         [0026]    In some embodiments, conductive plate inductance reducer  402  is configured to include a resistive component  404 . Resistive component  404  may be a discrete resistor coupled to conductive plate inductance reducer  402  or may be an integral characteristic of conductive plate inductance reducer  402  by appropriate selection of the plate thickness, size, material, and the like. Resistive component  404  in conductive plate inductance reducer  402  provides some additional damping during switching transitions to limit voltage overshoot and ringing. 
         [0027]    In the exemplary embodiment, conductive plate inductance reducer  402  is galvanically isolated. In other embodiments, conductive plate inductance reducer  402  is galvanically connected to ground, a node of the circuit in which it is located, or any other suitable reference. 
         [0028]    The exemplary conductive inductance reducers described herein negate a significant portion of the magnetic flux through the interior of a commutation loop, thereby reducing the inductance of the commutation loop. When the exemplary conductive inductance reducers are used in connection with switching circuits, the reduced inductance typically reduces voltage overshoot and ringing during switching transitions. Moreover, some exemplary conductive inductance reducers include a resistive component to provide additional dampening to the circuits in which the conductive inductance reducers are included. 
         [0029]    Exemplary embodiments of the systems and methods are described above in detail. The systems and methods are not limited to the specific embodiments described herein, but rather, components of the systems and/or steps of the methods may be utilized independently and separately from other components and/or steps described herein. For example, the system may also be used in combination with other apparatus, systems, and methods, and is not limited to practice with only the system as described herein. Rather, the exemplary embodiment can be implemented and utilized in connection with many other applications. Although specific features of various embodiments of the disclosure may be shown in some drawings and not in others, this is for convenience only. In accordance with the principles of the disclosure, any feature of a drawing may be referenced and/or claimed in combination with any feature of any other drawing. 
         [0030]    This written description uses examples to disclose the embodiments, including the best mode, and also to enable any person skilled in the art to practice the embodiments, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the disclosure is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.