Abstract:
An electrical distribution apparatus includes a fixed terminal, at least two fingers attached at respective pivot points in the apparatus, and a mechanical spring in operative communication with the at least two fingers, configured to provide tension upon separation of the at least two fingers. According to the apparatus, the at least two fingers are of a different length, length is a measure of the distance from a pivot point of a finger to an end of the finger, and the respective pivot points are each formed between the fixed terminal and each of the two fingers.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    Embodiments of the invention generally relate to electrical distribution devices, and more particularly to racking of electrical distribution devices, for example, circuit breakers. 
         [0002]    Conventional electrical distribution equipment generally includes one or more circuit breakers, and often includes a plurality of circuit breakers housed in drawout units in switchgear housings and other electrical equipment. Periodically, the circuit breaker drawout units require removal to facilitate maintenance and or replacement of the associated switching devices. Similarly, additional switching devices may be placed within the drawout units. In order to facilitate placement of additional devices and/or removal of existing devices, the circuit breaker is “racked in” or “racked out,” respectively. 
         [0003]    In general, a typical circuit breaker may be connected to the external power source through disconnects termed primary disconnects. The primary disconnects aid in connecting the circuit breaker to external power. The primary disconnects further aid the circuit breaker in being disconnected from the external power for maintenace or test procedures. Primary disconnects may also be termed clusters 
         [0004]    Typical circuit breakers have three positions. The first position is a “connected position” in which primary and secondary disconnects of the circuit breaker are connected to a circuit. The second position is a “disconnected position” in which the primary and secondary disconnects are disconnected. The third position is a “test position,” in which the primary disconnects are disconnected but the secondary disconnects are connected. The test position allows a user, for example, to check the functioning of secondary or control power. Breakers may be racked between these three positions. If racking in, the breaker is moved from the disconnected position, through the test position, into the connected position. If racking out, the breaker is moved from the connected position, through the test position, into the disconnected position. 
         [0005]    A racking mechanism is included in conjunction with the circuit breaker, such as a racking shaft, that allows for rotation of the mechanism to move the circuit breaker into the connected position. Furthermore, if a plurality of circuit breakers are included in a drawout box, additional racking mechanisms are used. It follows that as the number of primary disconnects or clusters increases, the force required for circuit breaker insertion/removal increases substantially. Thus, if more circuit breakers, or even larger circuit breakers, with differing current limiting requriements and/or thermal requriements are necessary for an application, breaker insertion/removal may be hindered due to large racking forces. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0006]    An embodiment of the invention includes an electrical distribution apparatus. The apparatus includes a fixed terminal, at least two fingers attached at respective pivot points in the apparatus, and a mechanical spring in operative communication with the at least two fingers, configured to provide tension upon separation of the at least two fingers. According to the apparatus, the at least two fingers are of a different length, length is a measure of the distance from a pivot point of a finger to an end of the finger, and the respective pivot points are each formed between the fixed terminal and each of the two fingers. 
         [0007]    Another embodiment of the invention includes an electrical distribution system. The system includes at least one electrical distribution apparatus and at least one terminal length arranged along a length or width of a footprint of an electrical distribution device configured as a fixed terminal. The apparatus includes the fixed terminal, at least two fingers attached at respective pivot points in the apparatus, and a mechanical spring in operative communication with the at least two fingers, configured to provide tension upon separation of the at least two fingers. According to the apparatus, the at least two fingers are of a different length, length is a measure of the distance from a pivot point of a finger to an end of the finger, and the respective pivot points are each formed between the fixed terminal and each of the two fingers. Furthermore, the at least one terminal length is in operative communication with the fingers of the apparatus between the pivot points. 
         [0008]    Another embodiment of the invention includes an electrical distribution system. The system includes a plurality of electrical distribution apparatuses, and at least one terminal length arranged along a length or width of a footprint of an electrical distribution device configured as a fixed terminal. The apparatuses include the fixed terminal, at least two fingers attached at respective pivot points in the apparatus, and a mechanical spring in operative communication with the at least two fingers, configured to provide tension upon separation of the at least two fingers. According to the apparatus, the at least two fingers are of a different length, length is a measure of the distance from a pivot point of a finger to an end of the finger, and the respective pivot points are each formed between the fixed terminal and each of the two fingers. Furthermore, the at least one terminal length is in operative communication with each of the plurality of fingers of the apparatuses between the pivot points. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0009]    These and other features, aspects, and advantages of the present invention will become better understood as the following detailed description is read with reference to the accompanying drawings in which like reference numerals represent like elements throughout the drawings, wherein: 
           [0010]      FIG. 1  illustrates diagrams of electrical distribution systems, according to example embodiments; 
           [0011]      FIG. 2  illustrates a diagram of an electrical distribution system, according to an example embodiment; 
           [0012]      FIG. 3  illustrates examples of electrical distribution systems, according to example embodiments; and 
           [0013]      FIG. 4  is a graph depicting experimental results of racking forces of different electrical distribution systems. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0014]    Detailed illustrative embodiments are disclosed herein. However, specific functional details disclosed herein are merely representative for purposes of describing example embodiments. Example embodiments may, however, be embodied in many alternate forms and should not be construed as limited to only the embodiments set forth herein. 
         [0015]    Accordingly, while example embodiments are capable of various modifications and alternative forms, embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that there is no intent to limit example embodiments to the particular forms disclosed, but to the contrary, example embodiments are to cover all modifications, equivalents, and alternatives falling within the scope of example embodiments. 
         [0016]    It will be understood that, although the terms first, second, etc. may be used herein to describe various steps or calculations, these steps or calculations should not be limited by these terms. These terms are only used to distinguish one step or calculation from another. For example, a first calculation could be termed a second calculation, and, similarly, a second step could be termed a first step, without departing from the scope of this disclosure. As used herein, the term “and/or” and the “/” symbol includes any and all combinations of one or more of the associated listed items. 
         [0017]    As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises”, “comprising”, “includes”, and/or “including”, when used herein, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. Therefore, the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments. 
         [0018]    It should also be noted that in some alternative implementations, the functions/acts noted may occur out of the order noted in the figures. For example, two figures shown in succession may in fact be executed substantially concurrently or may sometimes be executed in the reverse order, depending upon the functionality/acts involved. 
         [0019]    Hereinafter, example embodiments of the present invention will be described in detail. According to example embodiments, electrical distribution systems are provided which decrease the racking force of electrical distribution devices such as, for example, circuit breakers. The electrical distribution system includes multiple “fingers” for device racking. Each finger may be of a different length of an adjoining finger to reduce racking force of a device. The entry profile of the each finger may also be formed reduce racking force. Furthermore, the inclusion of multiple fingers allows for devices of different lengths and different frame sizes. The multiple finger assemblies may be staggered vertically or horizontally, in either coordinate axis direction, within a footprint of a device for relatively better thermal performance. 
         [0020]    Turning to  FIG. 1 , electrical distribution systems  101  and  110  are illustrated. System  101  is a simplified structure for illustration only. System  101  includes multiple assemblies of apparatuses  102 . Each apparatus  102  includes fingers  103  and  104 . The fingers  103  and  104  are of the same length, and have an inner curve  120 , or profile, which is formed to reduce racking force. Insertion of a device and racking force is described in detail with reference to  FIGS. 2 and 4 . 
         [0021]    System  110  is a simplified structure for illustration only as well. System  110  includes multiple assemblies of apparatuses  111 . Each apparatus  111  includes fingers  105  and  106 . The finger  105  is of a different length than finger  106 . For example, as illustrated finger  105  is relatively greater in length than finger  106 . Generally, a length difference of about ten percent (10%) to fifteen (15%) percent may be used according to some example embodiments. However, other example embodiments may includes greater difference in length or less difference in length, according to any particular implementation. As used herein, length may be a measure of length from a pivot point to an end of the finger. The fingers  105  and  106  have an inner curve  120 , or profile, which is formed to reduce racking force. Hereinafter, racking force and device insertion/removal is described with reference to  FIG. 2 . 
         [0022]    Turning to  FIG. 2 , an example electrical distribution system  210  is illustrated.  FIG. 2  includes two ( 2 ) separate views of the system  210 . In particular, VIEW A illustrates system  210  with a moving terminal  201  at an initial insertion of a device. VIEW B illustrates system  210  with a moving terminal  201  at an ending of an insertion of the same device. 
         [0023]    Focusing on VIEW A, moving terminal  201  is at an initial insertion of the device. Moving terminal  201  engages the fingers  202  of the system  210 , and would begin to separate the fingers  202  as the moving terminal  201  continues to be inserted. As the moving terminal  201  engages the fingers  202 , the inner curve  220 , or profile, of the fingers  202  direct the moving terminal  201  inward (or for example, towards the final insertion position of VIEW B). The fingers  202  further include locking profile  203 . 
         [0024]    The locking profile  203  (a recess in fixed terminal  210  and projection in the fingers  202 ) is used to arrest the movement of the fingers  202  in the horizontal axis (according to the arrangement of example  FIG. 2 ) and allow the fingers  202  to pivot about the recess  203 . Alternatively, the recess may be included in the fingers  202  and a projection may be included on the fixed terminal  210 . These locking features are advantageous in that they provide a pivoting action without additional mechanisms such as pins or holes. 
         [0025]    It follows that as the moving terminal  201  is inserted further into the system  210 , the moving terminal separates the fingers  202  and pulls the spring  204 . Thus, steady electrical contact between fingers  202  and moving terminal  201  is facilitated though continuous pressure provided with spring  204 . Further, as fingers  202  and fixed terminal  210  are in electrical contact, upon insertion of moving terminal  201 , electrical contact is established between moving terminal  201  and fixed terminal  210 . It is noted that although a coil spring is illustrated, example embodiments are not so limited. For example, any suitable spring may be used between the fingers  202 . For example, a leaf spring, cantilever spring, torsion spring, or any other suitable spring may be used. For example, if a torsion spring is used, it may be situated within pivot points of the fingers  202 . 
         [0026]    It also follows that as the moving terminal  201  is inserted, friction resists the inward motion and the separation of the fingers  202  resists the inward motion, resulting in “racking force”. However, as is readily apparent from the inner curve  220 , the reduced surface contact area  221  provided by the inner curve  220  reduces the friction, and thus the racking force. Furthermore, the outer portion of the inner curve  220  steadily separates the fingers  202  during the insertion of the moving terminal  201 , further reducing racking force. As described previously with reference to  FIG. 1 , multiple finger arrangements may be provided for accommodation of devices with larger footprints, greater current requirements, differing thermal requirements, and/or for any suitable purpose. Hereinafter, differing arrangements are discussed with reference to  FIG. 3 . 
         [0027]      FIG. 3  illustrates examples of electrical distribution systems, according to example embodiments. For example, a system may be formed of a plurality of apparatuses (see  FIG. 1 ) such that differing lengths of finger arrangements may be used for greater electrical contact surface area (which, for example, would increase thermal transfer contact area). System  301 , for example, includes terminal  310  which extends vertically through the racking system  301 . Terminal  310  may be considered either the moving terminal, or the fixed terminal, depending upon the orientation of the apparatus fingers. For example, with reference to  FIG. 2 , if the device includes the fixed terminal  202 , it follows that terminal length  310  is the fixed terminal. Alternatively, if the device includes the moving terminal  201 , it follows that the terminal length  310  is the moving terminal. Turning back to  FIG. 3 , the length of terminal  310  may be substantially the same length as the footprint of an electrical distribution device. Thus, an increased contact area may be facilitated through the greater length of the racking system  301  compared to conventional apparatuses. Furthermore, due to the increased contact area, greater thermal transfer may occur, resulting in the reduction of thermal issues. Moreover, the inner curve, or profile, of the apparatuses included in the system reduce the racking force apparent upon device insertion. Also, if fingers of differing lengths are also included, the racking force may be further reduced. 
         [0028]    System  302 , for example, includes terminals  320  which extend vertically through the system  302 . Each of terminals  320  may be considered either the moving terminal, or the fixed terminal, depending upon the orientation of the apparatus fingers. For example, with reference to  FIG. 2 , if the device includes the fixed terminal  202 , it follows that a terminal length of terminals  320  is the fixed terminal. Alternatively, if the device includes the moving terminal  201 , it follows that the terminal length or terminal  320  is the moving terminal. Turning back to  FIG. 3 , the terminals  320  may be substantially the same length as the footprint of an electrical distribution device. Furthermore, terminals  320  may be spaced horizontally to encompass more surface area of the footprint of an electrical distribution device. Thus, an increased contact area may be facilitated through the greater length of the system  302  compared to conventional apparatuses. Furthermore, due to the increased contact area, greater thermal transfer may occur, resulting in the reduction of thermal issues. Moreover, the inner curve, or profile, of the apparatuses included in the system reduce the racking force apparent upon device insertion. Also, if fingers of differing lengths are also included, the racking force may be further reduced. 
         [0029]    System  303 , for example, includes terminals  330  which extend horizontally through the system  303 . Each of terminals  330  may be considered either the moving terminal, or the fixed terminal, depending upon the orientation of the apparatus fingers. For example, with reference to  FIG. 2 , if the device includes the fixed terminal  202 , it follows that a terminal length of terminals  330  is the fixed terminal. Alternatively, if the device includes the moving terminal  201 , it follows that the terminal length or terminal  330  is the moving terminal. Turning back to  FIG. 3 , the terminals  330  may be substantially the same width as the footprint of an electrical distribution device. Furthermore, terminals  330  may be spaced vertically to encompass more surface area of the footprint of an electrical distribution device. Thus, an increased contact area may be facilitated through the greater width of the racking system  303  compared to conventional apparatuses. Furthermore, due to the increased contact area, greater thermal transfer may occur, resulting in the reduction of thermal issues. Moreover, the inner curve, or profile, of the apparatuses included in the system reduce the racking force apparent upon device insertion. Also, if fingers of differing lengths are also included, the racking force may be further reduced. 
         [0030]    System  304 , for example, includes terminals  340  which extend vertically through the system  304 . Each of terminals  340  may be considered either the moving terminal, or the fixed terminal, depending upon the orientation of the apparatus fingers. For example, with reference to  FIG. 2 , if the device includes the fixed terminal  202 , it follows that a terminal length of terminals  340  is the fixed terminal. Alternatively, if the device includes the moving terminal  201 , it follows that the terminal length or terminal  340  is the moving terminal. Turning back to  FIG. 3 , the terminals  340  may be substantially the same length as the footprint of an electrical distribution device. Furthermore, terminals  340  may be spaced horizontally to encompass more surface area of the footprint of an electrical distribution device. Thus, an increased contact area may be facilitated through the greater length of the racking system  302  compared to conventional apparatuses. Furthermore, due to the increased contact area, greater thermal transfer may occur, resulting in the reduction of thermal issues. Moreover, the inner curve, or profile, of the device securing apparatuses included in the system reduce the racking force apparent upon device insertion. Also, if fingers of differing lengths are also included, the racking force may be further reduced. 
         [0031]    Hereinafter, racking forces of different racking systems are compared using experimental results.  FIG. 4  is a graph depicting experimental results of racking forces of different electrical distribution systems. The graph includes force curves  401 ,  402 , and  403 . The vertical axis of the graph represents a value of force, and the horizontal axis represents the inward stroke of device insertion. For example, the motion of the moving terminal as described with reference to  FIG. 2 . Force curve  401  is a solid line representing the racking force profile of a conventional racking system design. For example, a design which excludes any features as described herein or is otherwise considered conventional. The curve  401  includes a sharp peak toward the first third of the inward stroke of device insertion. This peak is the maximum racking force, and may hinder the ability for proper insertion of electrical distribution devices. 
         [0032]    Force curve  402  is a dashed line representing the racking force profile of an example embodiment with a modified inner curve of device securing apparatus fingers. For example, a design which includes an inner curve of the fingers at least somewhat similar to curves  120  and  220  of  FIGS. 1-2 . The curve  402  includes a flattened peak toward the first third of the inward stroke of device insertion. This peak is the maximum racking force, and is of substantially reduced force compared to the conventional racking system curve  401 . Thus, device insertion may be relatively easier, which may result in proper insertion of electrical distribution devices. 
         [0033]    Force curve  403  is a dotted line representing the racking force profile of an example embodiment with a modified inner curve of device securing apparatus fingers, and including fingers of differing lengths. For example, a design which includes an inner curve of the fingers at least somewhat similar to curves  120  and  220  of  FIGS. 1-2 , and fingers of differing lengths as illustrated in  FIG. 1 . The curve  403  includes a flattened peak toward the first third of the inward stroke of device insertion with a local minimum along the flattened peak. The flattened peak is the maximum racking force, and is of substantially reduced force compared to the conventional racking system curve  401  and the force curve  402 . Thus, device insertion may be relatively easier than previously described approaches, which may result in proper insertion of electrical distribution devices. 
         [0034]    With only some example embodiments of the present invention having thus been described, it will be obvious that the same may be varied in many ways. The description of the invention hereinbefore uses these examples, including the best mode, to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention 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 languages of the claims. Such variations are not to be regarded as a departure from the spirit and scope of the present invention, and all such modifications are intended to be included within the scope of the present invention as stated in the following claims.