Patent Application
20070173133
The present invention relates to the field of electrical supply systems, and more particularly to the field of electrical feeder circuits. With even greater particularity, the invention relates to a modularized feeder circuit control panel for a power distribution center for underground mining activities.
In electrical supply and power distribution systems and more particularly to underground mining applications utilizing the same, the repair of power distribution centers, such as longwall power centers and longwall starters is presently a difficult task. Due to the rugged and demanding environments where this equipment is normally employed, the industry has traditionally relied upon solid bolted type or hardwired connections for the operative components and circuitry in these systems. The underlying logic behind these methods is the desire to eliminate any potential weak point in the circuitry that may be compromised due to the prevalence of dust, dirt, moisture and other environmental factors.
These same environmental considerations make repair and maintenance of the equipment a difficult task. Due to the extensive size of such equipment, it is impractical to evacuate defective equipment to the surface in order to provide a clean environment for the technician to effectuate the necessary repairs. Accordingly, repairs are made on site, thereby providing further opportunity for the infiltration of contaminants into the system as the technician must open the various access panels, leaving them open for extended periods of time. Moreover, the technician is left to effectuate the repairs in the austere environment. In such conditions and as a consequence of such bolted connections, repairs remain a time consuming, labor intensive proposition. Similarly, because the equipment remains in an inoperable condition for an extended period of time, there is a concomitant loss in productivity as the equipment reliant on the electrical power is rendered useless.
While there have been efforts in the industry to modularize critical components in these systems to improve the maintainability of the systems, their use remains limited.
The apparatus of the present invention is applicable for use in electrical power supply and distribution systems, and is particularly suited for underground mining operations. The apparatus comprises: a stationary frame supporting one or more main bus terminals and a plurality of power supply output terminals in spaced relation to each other such that no electrical connection is made between the main bus terminals and the power supply output terminals. A movable frame is slidably mounted to the stationary frame and supports one or more main bus terminal connectors and a plurality of power supply output connectors. The main bus terminal connectors and supply output connectors are positioned for mating engagement with the main bus terminals and power output terminals upon selective movement of the movable frame relative to the stationary frame. A disconnect mechanism is mounted to the movable frame and provides selective electrical connection between the main bus terminal connectors and the power supply output connectors. Preferably the disconnect mechanism is operable from outside said apparatus. An observation window in the face of the front panel of the device provides for visual confirmation of the connection status of the apparatus from outside the apparatus.
The disconnect mechanism comprises one or more contactors to selectably control the electrical conductivity of the apparatus between an closed conducting position and an open position. In the open position, the disconnect mechanism preferably connects output connectors to a grounded condition.
The movable frame is configured in a tray like manner to carry the electrical conducting and controlling components of the apparatus, such that repairs may be easily made by substitution of a defective tray with an operational tray. The defective tray may then be evacuated to a suitable repair site to return it to an operational condition.
An exemplary apparatus of the present invention is depicted in the accompanying drawings which form a portion of this disclosure and wherein:
Referring to the drawings for a fuller understanding of the invention,
Stationary frame 20 generally comprises a pair of longitudinal support rails 21, end supports 22, and a base plate 23 for supporting the electrical components carried by the stationary frame 20. Preferably base plate 23 will extend between support rails 21 and end supports 22 to prevent the infiltration of dust, moisture and other contaminants from beneath the apparatus which might adversely effect the longevity and performance of the electrical components.
Stationary frame 20 may further comprise a suitable enclosure (not shown) to protect the electrical components from the aforementioned environmental hazards, such that the apparatus may be utilized in a stand alone configuration. More preferably the apparatus will be utilized as component of a power distribution system, such as a longwall power center, in which case a separate enclosure would not be required.
Stationary frame 20 further provides support for one or more main bus input terminals 24, which receive electrical power inputs to the apparatus from the power distribution system or center, and one or more of power supply output terminals 25 which carry the electrical power from the apparatus to a selected piece of electrical equipment or feeder line. Terminals 24 and 25 are supported in spaced relation to each other such that no electrical connection is made between main bus input terminals 24 and power supply output terminals 25 unless an electrical connection is made through the other electrical components of the apparatus. That is, terminals 24 and 25 are mounted to the apparatus such that they are electrically isolated from each other and the apparatus. In the particular embodiment shown, terminals 24 and 25 are mounted in a linear arrangement on an isolating support member 26, and is by no means limiting. Preferably, isolating support member 26, will serve as the rear panel 70, to which the respective input and output power cables are connected.
Movable frame 30 comprises a pair of longitudinal support members 31 extending from front panel 50 and a support tray 32 disposed between support members 31 and front panel 50. Support members 31 are selected to cooperatively engage longitudinal support rails 21 such that movable frame 30 is slidable relative to and within stationary frame 20. Preferably, one or more rollers 33 are attached to each longitudinal support member 31, such that rollers 33 engage longitudinal support rails 21 in rolling contact, permitting relatively easy movement of moveable frame 30 between an open and a closed position.
The support tray 32 of movable frame 30 provides support and mounting for one or more main bus input connectors 34 and one or more power output connectors 35 in spaced relation and positioned for mating engagement with main bus input terminal 24 and said output terminal 25 upon movement of movable frame 30 to a closed position relative to stationary frame 20. In the embodiment shown, connectors 34 and 35 and terminals 24 and 25 are standard heavy duty male and female insulated connectors having an outer insulating layer 27 and 37, and a conductor 28 and 38 disposed internally of the insulating layers 27 and 37.
Electrical connection between main bus input connector 34 and power output connector 35 is provided via a disconnect mechanism 40, selectable between a closed, conducting position, and an open position. In the embodiment shown, standard heavy duty switch gear 60 having contactor 61 is interposed between input connectors 34 and output connectors 35, with connectors 34 and 35 communicating with the contactor 61 via a conductor 38, such as a heavy duty electrical cables. With the engagement of connectors 34 and 35 to terminals 24 and 25 upon closure of the movable frame 30, selective electrical conductivity is provided between the main bus input terminals 24, providing the incoming electrical power source, and the power output terminals 25, feeding the electrical power to the equipment, via switch gear 60 and associated contactors 61.
Switch gear 60 and contactors 61 are supported by and movable with support tray 32 and provide an electrically isolated conductive pathway for the electrical power carried by the apparatus. As may be seen in reference to
As best seen in
For mining applications in particular, it is desirable that any spark that may be developed as a consequence of breaking electrical conduction through the apparatus be contained within the enclosure or host distribution panel so as to reduce the risk of explosion. More preferably, contactor 61 is a spark arresting type, such as a vacuum break, such that opening disconnect 40 will automatically open contactor 61, forcing any load break arching to be contained within the vacuum bottles of the contactor 61. This may be accomplished by one or more limit switches 65 sensing and communicating the selected position of disconnect mechanism 40 to contactor 61. An exemplary limit switch 65 is shown in
For safety and other operational considerations, electrical conduction between input terminals 24 and output terminals 25 should be broken before movable frame 30 is repositioned within stationary frame 20. This is done so as to prevent arching between terminals 24 & 25 and their associated connectors 34 & 35 as they are electrically coupled or decoupled when the movable frame 30 is repositioned within stationary frame 20. Accordingly, disconnect mechanism 40 should further comprise one or more interlocks to limit movement of movable frame 30 to conditions when conductivity between input terminal 24 and output terminals 25 has been broken.
An exemplary mechanical interlock may be seen in reference to
Alternatively, disconnect mechanism 40 may further comprise an electro-mechanical interlock 46, seen in
In addition to the aforementioned spark hazard, exposure of personnel to the high voltage electricity carried by the apparatus is also a hazard. In this regard, repositioning movable frame 30 to its open position will automatically break electrical connectivity between terminals 24 and 34 and their associated connectors 25 and 35 such that no electrical load can carried by contactor 61 and its associated conductors 38. The components of the movable tray may then be repaired without risk of electrical shock to maintenance personnel.
For maintenance and diagnostic purposes, it is often desirable to be able to test the functioning of switch gear 60 and contactors 61 and other sensors, relays, and electrical components while the movable frame 30 is open. In order to do so, it is necessary that actuating lever 44 be placed in its closed position such that limit switches 65 may be closed. In this condition, inadvertent closure of the movable tray 30 and possible engagement of terminals 24 & 25 with connectors 34 & 35, would potentially reintroduce both the spark and electrical shock hazards to the environment. Accordingly, a mechanical stop to prevent inadvertent closure of movable frame 30 is highly desirable. In this regard, the exemplary mechanical detent flange 41 also serves to prevent inadvertent closure of movable frame 30. As may be seen in reference to
To prevent inadvertent movement of actuating lever 44, a mechanical stop may optionally be provided. As may be seen in reference to
As an added safeguard, movable frame 30 should be secured to stationary frame 20 so that only properly authorized personnel are provided access to open the tray for servicing or otherwise. This may be achieved by one or more bolts or pins 55 securing front panel 50 to stationary frame 30. Due to the extreme operating conditions contemplated for the apparatus, over time terminals 24 and 25 may become difficult to disengage from connectors 34 and 36 or the interface between rails longitudinal support rails 21, longitudinal support members 31, and rollers 33 may become such that the apparatus is difficult to open. To alleviate these difficulties, the apparatus may be provided with an actuator 56, such as a worm screw, operatively coupled between front panel 50 and stationary frame 20 such that actuator 56 will disengage movable frame 30 from stationary frame 20. Actuator 56 may also be utilized in a reverse direction to draw the movable frame 30 into stationary frame 20 to securely close the apparatus and ensure full engagement of terminals 24 and 25 with connectors 34 and 35. Actuator 56 may be rotated by a wrench 57 or other suitable means.
In mining applications in particular, the environmental and operational constraints make repair of the electrical components of the apparatus within the confines of the mine a difficult endeavor. A particularly useful aspect of the present invention concerns the rapid repair or replacement of a defective apparatus such that the process for which the electrical power is provided experiences minimal interruption. Because the operative electrical components are carried by the movable frame 30 in a modular package, a defective assembly may be quickly replaced by completely removing the defective movable frame 30, and replacing it with an operational one, thereby permitting rapid resumption of the production process. The defective components may then be repaired by evacuating movable frame 30 to a more suitable repair site or facility.
Controls 51 for operating the apparatus are mounted on front panel 50, such that the device may be readily controlled when the apparatus is inserted into a power distribution panel, which would otherwise block access to the same. In operating feeder circuits such as that disclosed in the present invention, it is desirable to monitor conditions of the apparatus and various parameters for the electricity carried therein to for conditions such as short circuits, overloads, ground faults, overvoltages and undervoltages.
These parameters and the apparatus conditions may be monitored or controlled by a controller 52 integrally mounted to front panel 50. Controller 52 may contain integrated logic circuitry and protective relays such that the apparatus is capable of controlling and monitoring its electrical condition independent of a host power distribution system. Additionally, controller 52 may communicate its electrical condition and status to a host power distribution center via electrical, fiber optic or other suitable cabling. It may also receive and respond to control signals via such cables. Alternatively, the apparatus may contain a transmitter and/or receiver to accomplish the same end. In either case, it may be desired to provide complete remote control of the apparatus via computer interface of all functions, relay settings, and data acquisition. In the case where a control cable (not shown) is utilized to provide control and/or monitoring of the apparatus, the cable should be detachably coupled to the controller 52 via a control cable interface 54, such that the movable frame 30 may be readily removed. Thus, movable frame 30 is preferably equipped to carry all the necessary circuitry, sensing devices and protective relaying for an entire feeder circuit. This configuration will permit rapid repair of a defective feeder circuit by substitution of an operable one.
Because power distribution systems and the equipment dependent thereon may require feeder circuits having varying electrical inputs, outputs, conditioning or tolerances, it is preferred that the electrical components of a given movable frame 30 be matched to the required parameters. To accomplish this, movable frame 30 should be matched to the corresponding stationary frame 20. For example, movable frame 30 may be keyed to stationary frame 20 such that only a movable frame 30 with compatible electrical components will fit within fixed frame 20. Such a configuration is desirable to preclude, for example, a tray with a 200 amp rating being inserted into a feed designed to run 600 amp equipment. Alternatively, the spaced alignment of terminals 24 & 25 supported by stationary frame 20 may be keyed to a set of desired operating characteristics for the feeder circuit or power distribution system. In this case, a movable frame 30 carrying a compatible set of electrical components, corresponding to the desired set of operating characteristics for the feeder circuit will have its connectors 34 & 35 aligned for engagement with terminals 24 & 25. The alignment of connectors 34 & 35 on an incompatible tray would not engage with terminals 24 & 25. A similar result could be obtained with a slot and pin arrangement wherein the movable tray 30 could only engage stationary frame 20 when the slot and pin of compatible units are aligned. A preferred embodiment of this is shown in
Alternatively, where control circuitry is utilized, the electrical components carried by movable frame 30 may be programmably configured such that its variable parameters may be automatically configured to match the newly inserted tray to the particular parameters required based on its position within the power distribution system. In this regard, carriage of all the necessary components for a desired feeder circuit on movable frame 30 permits a rapid reconfiguration of the feeder circuit to one with the desired operating parameters.
It is to be understood that the form of the invention shown is a preferred embodiment thereof and that various changes and modifications may be made therein without departing from the spirit of the invention or scope as defined in the following appended claims:
