Abstract:
A removable contactor drawer including a transitional chamber receivable in a fixed casing. The transitional chamber including electrical components for an electrical feeder circuit. The fixed casing being designed to be mounted and used within a power distribution center and has input connectors for the incoming electrical power. Source power may be channeled through the electrical components via the fixed casing and delivered to a power outlet on a front face of the transitional chamber. The transitional chamber may optionally contain equipment to monitor and report operational faults within the contactor drawer. A front-mounted motor drive allows a remotely located operator to perform removal of the transitional chamber while under power, thus providing protection against the danger of arc flash.

Description:
FIELD 
     The subject matter of the present specification relates to a removable contactor drawer such as an electrical vacuum contactor removable drawer used in electrical supply systems, and especially to the realm of electrical feeder circuits. More specifically, the removable contactor drawer relates to a modularized feeder circuit control panel for a power distribution system such as power distribution systems used in mines. 
     BACKGROUND 
     In electrical supply and power distribution centers, and especially in power distribution centers used in mining operations, the repair of power distribution centers while energized is usually a challenging endeavor. The power centers are often located underground and are frequently situated far from modern conveniences. The environment in which power distribution centers and driven equipment are normally located is dark, dirty, dusty, rugged, damp, and fraught with safety hazards. In the event of an electrical or mechanical failure of such equipment, it is usually quite difficult to evacuate defective equipment outside the mine to a clean environment for a technician to accomplish any necessary repairs. Due to the extensive size of such equipment and due to production demands and requirements, the technician must often accomplish any necessary repairs in the mining environment. Similarly, because the equipment remains in an inoperable condition for an extended period of time, there is a corresponding loss in productivity as the equipment reliant on the electrical power is idled. 
     SUMMARY 
     In at least one exemplary embodiment of the subject matter of the present specification, a removable contactor drawer may include a vacuum contactor removable drawer applicable for use in electrical power supply and distribution systems. The removable drawer is particularly suited for mining operations. The removable drawer includes a fixed casing with mounted main bus supply connectors and provides for power output to a vacuum contactor or other switching and/or control instruments. A removable transitional chamber is mountable to the fixed casing and may support the vacuum contactor or other switching and/or control instruments, as well as receiving power connectors. The main bus supply connectors and the receiving power connectors are positioned for mating engagement upon selective movement of the transitional chamber relative to the fixed casing. An observation window in the face of the front panel may be included to provide visual confirmation of the functional status of fuses within the transitional chamber from outside the removable drawer. 
     In an exemplary embodiment, the transitional chamber is configured in a tray-like manner to carry the electrical conducting and controlling components of the removable drawer such that repairs may be easily made when all components are de-energized. An example of a typical repair is the removal and replacement of a defective fuse. When such a repair is made, the same transitional chamber may be immediately returned to service by being reinserted into the fixed casing. Alternatively, a new or different transitional chamber that is operable may be substituted for a defective transitional chamber and the defective transitional chamber may then be evacuated to a suitable repair site. 
     In an exemplary embodiment, the removable contactor drawer features output power distributed through the front of the drawer, preferably through an outlet which in turn feeds power into a plug and to a trailing cable. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The subject matter of the present specification will now be explained in more detail using exemplary embodiments, which are not exclusive, and with reference to the attached drawings, in which: 
         FIG. 1  is a schematic drawing of an exemplary electrical system and power center supporting the removable contactor drawer; 
         FIG. 2  is a perspective view of an exemplary embodiment of a fixed casing of the removable contactor drawer; 
         FIG. 3  is a perspective view of an exemplary transitional chamber of the removable contactor drawer; 
         FIG. 4  is a perspective view of an exemplary motor and remote control instrument of the removable contactor drawer; 
         FIG. 5  is a perspective view of an exemplary worm actuator, and actuator catch for use in a transitional chamber of the removable contactor drawer; and 
         FIG. 6  is a perspective view of a preliminary stop device. 
     
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     In mining applications in particular, the environmental and operational constraints render repair of the electrical components of the equipment used in the electrical supply and power distribution systems within the confines of the mine a difficult mission. To overcome the difficulties encountered during such repairs, the removable contactor drawer provides for the rapid repair or replacement of defective equipment such as a blown fuse  22  thereby effectuating minimal interruption of operating equipment  93  for which the electrical power is provided. Because the operative electrical components of mining power distribution centers are carried primarily by the transitional chamber  20  in a modular package, a defective assembly and/or item may be quickly replaced by completely removing the defective transitional chamber  20 , and replacing the chamber with an operational chamber, thereby permitting rapid resumption of the mining processes. The defective components may then be repaired by evacuating transitional chamber  20  to a repair site or facility designed for maintenance. In addition, replacement of one or more fuses  22 , for example, attached to a vacuum contactor  30  or other switching and/or control instruments is a simple process, requiring merely for the drawer to be disengaged for a brief time while replacement of any such defective or blown fuses  22  is accomplished. 
       FIG. 1  depicts a typical schematic of a basic power center  94  used, for example, in a mine. As shown in  FIG. 1 , power from a utility company  90  is supplied through a substation  91 , where the voltage is stepped down prior to entering the power center  94 . The voltage may then be stepped down again at a mine transformer  92 . The stepped down power is then distributed to one or more fixed casings  10  in the power center  94 . In an exemplary embodiment, the power center  94  may include a housing and/or frame (not shown) to which the fixed casing(s)  10  may be attached. Power is delivered through the fixed casing(s)  10  to a transitional chamber  20  in the fixed casing  10  to a plug  27  and trailing cable  28  and then to the driven operating equipment  93  (such as mining equipment, ventilation equipment, etc.). The power center  94  may include many removable contactor drawers  10 ,  20  (stacked vertically and/or horizontally) therein. 
       FIG. 2  depicts an exemplary embodiment of a fixed casing  10  of the removable contactor drawer. The fixed casing  10  is mounted to the power center  94  to provide an interface between input power and the operating equipment  93 . As shown in  FIG. 2 , the fixed casing  10  provides support for one or more main bus input connectors  12 , which receive electrical power input to the drawer from the mine transformer  92 . The main bus input connectors  12  are mounted to a nonconductive mounting board  15 , which in turn is mounted to a rear panel  11  of the fixed casing  10 . Support members  13  may be provided on the fixed casing  10  to receive and operatively guide a transitional chamber  20  into fitting contact with the main bus input contactors  12 . In an exemplary embodiment, the support members  13  may be guide rails that receive a corresponding element on the transitional chamber  20  thereby providing linkage with the transitional chamber  20 . The fixed casing  10  may also include an actuator catch  51  described in more detail below. 
       FIG. 3  depicts an exemplary embodiment of a transitional chamber  20  of the removable contactor drawer. As shown in  FIG. 3 , the transitional chamber  20  may include a support tray  31  and a front panel  21  at a first end of the tray  31 . The transitional chamber  20  may also include a pair of longitudinal support members  32  extending from the front panel  21  to connector bracket  34  located at an opposite end of the support tray  31 . Receiving connectors  29  are secured to a nonconductive mounting board  35  located in the connector bracket  34 . 
     The receiving connectors  29  are positioned for mating engagement with the main bus input connectors  12  of the fixed casing  10  when the transitional chamber  20  is inserted into the fixed casing  10 . In an exemplary embodiment, electrical power from the main bus input connectors  12  of the fixed casing  10  is fed through the receiving connectors  29  of the transitional chamber  20  to one or more vacuum contactors  30  or other switching and/or control instruments in the transitional chamber  20  through fuses  22  and ultimately to a power outlet  26  located on the front panel  21  of the drawer. Power may then be fed from the power outlet  26  into a plug  27  and to a trailing cable  28 , and eventually to driven operating equipment  93 . 
     In an exemplary embodiment, the transitional chamber  20  may further include controls  23  mounted on the front panel  21  for operating the removable drawer, such that the components within the transitional chamber  20  may be readily monitored and controlled when the drawer  10 ,  20  is installed into the power center (e.g., a power distribution panel). During operation of the removable contactor drawer, it is desirable to monitor conditions of the components and their respective parameters for the electricity carried therein for changes such as short circuits, overloads, ground faults, overvoltages, undervoltages, overcurrents, phase imbalances, and the like. In an exemplary embodiment, visual surveillance of the components, such as the fuses  22 , can be performed through an observation window  25 . 
     In use, the transitional chamber  20  of the drawer is inserted into, or otherwise operatively engaged with, the fixed casing  10 . In an exemplary embodiment, the support members  13  of the fixed casing  10  cooperatively engage the longitudinal support members  32  of the transitional chamber  20  such that transitional chamber  20  slides into fixed casing  10 . In an exemplary embodiment, engagement between the transitional chamber  20  and the fixed casing  10  may be enhanced with the use of rollers  33 , which may be attached to either the transitional chamber  20  or the fixed casing  10 . In an exemplary embodiment, the rollers  33  may be affixed to the longitudinal support members  32  of the transitional chamber  20  and be received in rolling contact with the support members  13  of the fixed casing  10 . 
     In an exemplary embodiment, the removable contactor drawer  10 ,  20  may further include features for mitigation of the danger of arc flash that may occur when the transitional chamber  20  and the fixed casing  10  are being engaged and/or disengaged from one another. As discussed above, the main bus input connectors  12  are mounted to the nonconductive mounting board  15 , and the receiving connectors  29  are mounted to the nonconductive mounting board  35 . In addition, the removable contactor drawer  10 ,  20  may include an arc flash shield  14  mounted to the fixed casing  10  ( FIG. 2 ). The arc flash shield  14  is configured to suppress an electrical arc or spark that could injure an operator during engagement and/or disengagement of the transitional chamber  20  and the fixed casing  10 . Moreover, arc flash in a mining environment could cause catastrophic injury and damage. 
     To further protect against injury to an operator resulting from arc flash, insertion or removal of the transitional chamber  20  from the fixed casing  10  may be performed remotely.  FIG. 4  shows a motor  40  and remote control box  41  in an exemplary embodiment of a remote operating instrument. The motor  40  and remote control box  41  allow for remote insertion or removal of the transitional chamber  20  from the fixed casing  10  to be accomplished while mine power is energized, thus keeping the operator or service technician away from the area of arc flash danger. Although an exemplary motor  40  and remote control box  41  are depicted in  FIG. 4 , the subject matter of the present application is not limited to the exemplary embodiment. Other systems and methods of remotely operating the drawer are contemplated herein without departing from the scope of the present application.  FIG. 5  shows an exemplary embodiment of operational structure that may be used in the remote insertion and withdrawal of the transitional chamber  20  from the fixed casing  10 . As shown in  FIG. 5 , engagement and disengagement of the transitional chamber  20  from the fixed casing  10  may be accomplished using a worm actuator  50  driven by the motor  40  and configured to engage the actuator catch  51  ( FIG. 2 ). The motor  40 , and therefore movement of the transitional chamber  20  of the drawer relative to the fixed casing  10 , is activated using the remote control box  41 . 
     Alternatively, the worm gear  50  may be driven manually using a wrench (not shown) fitted to drive the worm gear  50 . Although a drive system including a worm gear  50  and actuator catch  51  is depicted in  FIG. 5 , the subject matter of the present application is not limited to the exemplary embodiment. Other systems and methods of operating the drawer are contemplated herein without departing from the scope of the present application. 
     In an example embodiment, the motor  40  is prevented from being used while the plug  27  and trailing cable  28  are in place due to spacing limitations. This spacing feature provides an additional measure of safety because no current can be flowing through the power outlet  26  at the time when the motor  40  is attached or removed. 
     In an example embodiment, to further protect against the danger of arc flash, one or more vented slots or louvered openings  95  may be included in the rear panel  11  of the fixed casing  10  to allow arc flash to be routed away from the vicinity of operators and other personnel to the inside of the power center  94 . 
     Arc flash danger may also be reduced through the use of one or more angle supports  96  to prevent or mitigate damage to the top rear of the fixed casing  10  during an arc flash by reinforcement of the structural integrity of the arc flash shield  14 . 
     In an example embodiment, a preliminary stop device  97  may be used to keep the transitional chamber from being unintentionally dropped from the fixed casing. The preliminary stop device  97  is depicted in  FIG. 6 . This feature protects workers and other personnel from harm during in-place repairs of the transitional chamber and/or associated equipment. The preliminary stop device  97  consists of one or more small plates welded or otherwise secured to the support members of the fixed casing  10 . When the transitional chamber  20  is being removed from the fixed casing  10 , the rollers  33  come into contact with the preliminary stop device  97  and prevent removal unless extra lifting force is applied. 
     In an example embodiment, the drive unit for the transitional chamber cannot be attached with the trailing cable engaged, thereby assuring that power downstream from the transitional chamber is shut off during such maintenance work. 
     The general concept stated herein may be changed and/or modified without departing from the model defined in this document. Exemplary embodiments being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the present invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.