Abstract:
The present invention provides an improved fused disconnect. More specifically, the present invention provides a fusible disconnect that includes a single line side terminal, two independent load side terminals, two independent removable fuse carriers and two independent blown fuse indicators. The common line side terminal provides power to both of the removable fuse carriers. The present invention therefore enables a single, standard sized disconnect to isolate and provide overload protection for two electrical load devices, thus reducing the required number of fused disconnects by one half. The present invention also reduces the required number of line side connections by one half. To this end, in an embodiment of the present invention, a multiple pole fused disconnect includes a housing, a line terminal secured to the housing and a plurality of load terminals secured to the housing. The fused disconnect also includes a pair of fuses each electrically communicating with the line terminal and a load terminal.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates, generally, to fuse-protected electrical disconnects for power distribution systems. More particularly, the present invention relates to low voltage, high current electrical disconnects having load side and line side terminals.  
           [0003]    2. Description of the Prior Art  
           [0004]    Power distribution systems, such as those used in telecommunications applications, often need to deliver low voltage but high current electrical power to devices that require this power to operate. These power systems must provide uninterrupted operation and usually rely on batteries to supply instantaneous back-up power if necessary. In these systems, it is sometimes necessary to disconnect power to various pieces of equipment, or small groups of equipment, so that operators can perform maintenance. It is also necessary to provide overload protection for the equipment on an individual basis, so that operators can diagnose malfunctioning electrical devices.  
           [0005]    For these reasons, multiple levels of power distribution are used with larger fused disconnects feeding smaller fused disconnects. For example, a single large fused disconnect, ranging in operation from 600 to 1200 Å, can distribute power to many smaller fused disconnects having loads in the range of 1 to 90 Å in normal operation. Each of these smaller loads should have their own disconnect as well, so that operators can perform maintenance on a specific load device without interrupting the operation of other load devices. Large power distribution systems including telecommunications systems, which supply many electrical devices, therefore require many individual fused disconnects.  
           [0006]    Power system enclosures or power distribution frames are designed to receive a standard sized fused disconnect, which is approximately one inch wide by five inches high. Known fused disconnects typically include a housing having, among other items, a line side terminal connected to a power supply line bar, a single load side terminal that enables an electrical connection to a single load device and a single removable plug-in fuse carrier. Some known disconnects also provide an alarm circuit connected in parallel with the main fuse. The alarm circuit provides either local or remote blown fuse indication.  
           [0007]    The cumulative effect of these standard sized disconnects is that they take up a large amount of valuable space within the power system enclosure or distribution frame. Typical enclosures, housing up to 128 individual disconnects in a row, fill up quickly. Furthermore, properly maintained large power systems leave adequate room for additional load devices. Since the size of the disconnect housing has been standardized and distribution frames have been fabricated according to the space requirements of such housings, a need exists to optimize the design of existing disconnect assemblies.  
         SUMMARY OF THE INVENTION  
         [0008]    The present invention provides an improved fused disconnect. More specifically, the present invention provides a fusible disconnect that includes a single line side terminal, two independent load side terminals, two independent removable fuse carriers and two independent blown fuse indicators. The common line side terminal provides power to both of the removable fuse carriers. The present invention therefore enables a single, standard sized disconnect to isolate and provide overload protection for two electrical load devices, thus reducing the required number of fused disconnects by one half. The present invention also reduces the required number of line side connections by one half.  
           [0009]    To this end, in one embodiment of the present invention, a multiple pole fused disconnect housing includes a line terminal, a plurality of load terminals and a pair of fuse connectors for each load terminal. Each pair of fuse connectors is adapted to receive a fuse.  
           [0010]    In an embodiment, the housing has a cavity associated with each pair of fuse connectors and each cavity is adapted to receive a fuse. In an embodiment, the fuses are housed in a carrier and each cavity is adapted to receive a fuse carrier.  
           [0011]    In an embodiment, the housing is physically dimensioned to require no more mounting space on a standard power distribution frame than does a standard single fuse housing.  
           [0012]    In an embodiment, each pair of connectors electrically communicates with the line terminal and a load terminal. In an embodiment, one connector of each pair electrically communicates with a blown fuse indicator. In an embodiment, the blown fuse indicator includes a light emitting diode.  
           [0013]    In another embodiment of the present invention, a multiple pole fused disconnect includes a housing, a line terminal secured to the housing and a plurality of load terminals secured to the housing. The fused disconnect also includes a pair of fuses each electrically communicating with the line terminal and a load terminal.  
           [0014]    In an embodiment, the line terminal electrically communicates with a blown fuse indicator. In an embodiment, the fuses are housed in a carrier.  
           [0015]    In an embodiment, the housing has a cavity associated with each fuse, wherein the cavities are each adapted to receive either a fuse or a fuse carrier. In an embodiment, the housing has a cavity associated with each fuse, wherein the cavities are each adapted to receive identically sized carriers.  
           [0016]    In an embodiment, the fuses have different current ratings. In an embodiment, the fuses have current ratings from one to ninety amps.  
           [0017]    In an embodiment, the fuses include blown fuse indicators. In an embodiment, the fuse carriers include fused alarm switches in electrical communication with the fuses.  
           [0018]    In an embodiment, the housing is physically dimensioned to require no more mounting space on a standard power distribution frame than does a standard single fuse housing.  
           [0019]    In an embodiment, the housing includes a plurality of pairs of fuse connectors, each pair of fuse connectors adapted to electrically communicate with a fuse. In an embodiment, the housing includes a plurality of pairs of conductive clips, each pair of clips adapted to press-fit onto a pair of fuse contacts associated with the fuse.  
           [0020]    In a further embodiment of the present invention, a method of providing fuse-protected electrical disconnects for a plurality of individual load-side devices in a power distribution system includes the following steps. An operator connects a single industry-standard size electrical disconnect housing to a power distribution frame, wherein the housing includes one line terminal and a plurality of load terminals. The operator connects a plurality of fuses to the housing, wherein each of the plurality of fuses is in electrical communication with the line terminal and a respective one of the plurality of load terminals. The operator connects the line terminal to line-side power. The operator lastly connects each of the plurality of load terminals to a respective one of the plurality of individual load-side devices.  
           [0021]    In this method, the space required along the power distribution frame for the housing is no greater than the space required for a single industry-standard size electrical disconnect. That is, the housing of the present invention requires the same space as those disconnects providing only one line terminal and only one load terminal and being adapted to connect only one fuse therebetween.  
           [0022]    An advantage of the present invention is to provide double the amount of electrical devices that can be connected to a standard sized fused disconnect.  
           [0023]    Another advantage of the present invention is to reduce the number of required load side connections in a power distribution frame by one half.  
           [0024]    A further advantage of the present invention is to provide a housing that is compatible with existing enclosures or power distribution frames.  
           [0025]    Yet another advantage of the present invention is to provide individual blown fuse indication for each fuse, as well as to isolate secondary fuse alarms from the housing to reduce the frequency of false alarms.  
           [0026]    Additional features and advantages of the present invention will be described in, and apparent from, the following Detailed Description of the preferred embodiments and the Drawings. 
       
    
    
     DESCRIPTION OF THE DRAWINGS  
       [0027]    [0027]FIG. 1 is an elevation sectional view of one embodiment of the multiple pole fused disconnect of the present invention;  
         [0028]    [0028]FIG. 2 is a partial schematic, partial block diagram of the electrical circuit formed by the multiple pole fused disconnect of the present invention;  
         [0029]    [0029]FIG. 3 is an elevation sectional view of one embodiment of the plug-in fuse carrier of the present invention; and  
         [0030]    [0030]FIG. 4 is an elevation sectional view of one embodiment of the multiple pole fused disconnect of the present invention illustrated in combination with inserted fuse carriers. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0031]    Referring now to the drawings and in particular to FIG. 1, one embodiment of the multiple pole fused disconnect  10  of the present invention is illustrated. The disconnect  10  includes a housing  12  having a pair of mounting flanges  14 , which define a pair of mounting holes  16 . The housing  12  is preferably made of an electrically insulative, flame retardant plastic such as glass-filled polyester. The flanges  14  and mounting holes  16  are preferably formed to enable the disconnect  10  to be conveniently mounted in conventional enclosures or power distribution frames for large power systems. The dimensions of the housing  12  and the footprint defined by the mounting holes  16  preferably comply with industry standards and most preferably enable circuit breakers to be easily replaced. In one embodiment, the mounting holes are sized for a No. 6 screw.  
         [0032]    The plastic housing  12  includes a top wall  18 , a bottom wall  20  and a number of back walls  22   a  through  22   c , which are disposed at different horizontal dimensions from a front wall  24 . The different horizontal dimensions of the back walls  22   a  through  22   c  facilitate the housing of various components of the disconnect  10  and the electrical connection of associated wires. Meanwhile, the front wall  24  remains substantially flat for operator viewing and for fuse carrier insertion and removal.  
         [0033]    The front wall  24  defines a number of apertures  26  and  28 , through which the operator inserts or removes the fuse carriers. While the present embodiment illustrates two apertures  26  and  28 , for two fuse carriers, the present invention is not limited to two and alternatively provides three or more apertures for three or more fuse carriers. The front wall further defines a plurality of apertures  30 . The apertures  30  receive a plurality of blown fuse indicators. The operator readily sees the blown fuse indications, which face outward from the front wall  24 .  
         [0034]    The housing  12  includes a number of inner walls  32  and  34 . The inner walls  32  and  34  are preferably insulative plastic and electrically isolate different conductive materials within the housing  12 . The inner walls  32  and  34  also provide support for the conductive materials during and after assembly of the housing  12 . The housing  12 , which includes one or more molded plastic pieces, is adaptable such that one or both or a portion of one or both of the inner walls  32  and  34  are integrally formed with the outer walls of the housing. The housing  12  is further adaptable to be molded via any known technique.  
         [0035]    The housing  12  includes side walls  36  (one illustrated in section view), which together with the apertures  26  and  28 , defined by the front wall  24 , form insulated plastic cavities within which the fuse carriers slide into and become housed. The back wall  22   c  defines an aperture  38 , through which the disconnect  10  electrically communicates with a line wire. The top wall  18  defines apertures  40  and  42 , through which the disconnect  10  electrically communicates with a number of load wires.  
         [0036]    The housing  12  includes a conductive line conductor  44 , which in one embodiment is made of copper or copper alloy. The line conductor  44  is adaptable to be made of a single piece of conductive material or to include a number of fused or otherwise fixed conductive pieces. One end of the line conductor  44  terminates and defines a line terminal  46 . The line terminal  46  provides any known form of electrical connection including soldering posts and quick disconnects. In one preferred embodiment, the line terminal  46  provides an aperture and a lug nut  48 . The operator electrically connects a line wire  50  to the line terminal  46  by compressing the line wire  50 , or a suitable connector attached thereto, between the lug nut  48  and a lockwasher and screw  52 .  
         [0037]    The opposing end of the line wire  50  terminates with an electrical connection to the line bar power supply (not illustrated) located within the power distribution enclosure or frame. The line wire  50  is appropriately sized to handle the accumulated current of the multiple pole outputs and therefore may be of a thicker gage than the load wires. The line wire  50  is preferably copper or copper alloy stranded wire, which is suitably electrically insulated.  
         [0038]    The housing  12  includes a first conductive load device conductor  54 , which in one embodiment is made of copper or copper alloy. The first load conductor  54  is adaptable to be made of a single piece of conductive material or to include a number of fused or otherwise fixed conductive pieces. In one preferred embodiment, the first load conductor  54  is suitably bent from one piece of metal to provide a desired shape and rigidity for electrically connecting to various devices. One end of the first load conductor  54  terminates and defines a first load terminal  56 . The first load terminal  56  again includes any known form of electrical connection and preferably defines an aperture. The operator electrically connects a first load wire  58  to the first load terminal  56  by compressing the first load wire  58 , or a suitable connector attached thereto, between a screw  60  and a lockwasher and nut  62 .  
         [0039]    The opposing end of the first load wire  58  terminates with an electrical connection to a first electrical device or load device. The first load device can have a fuse rating of between one and ninety amps. This range covers most electrical applications from, but not including, the circuit board level up to and including electric motors and the like. The first load wire  58  is appropriately sized to handle the load current required by the electrical device. The first load wire  58  is preferably copper or copper alloy stranded wire, which is suitably electrically insulated.  
         [0040]    The opposing end from the first load terminal  56  on the first load conductor  54  defines a fuse connector or clip  64 , which is adapted to receive and removably hold a plug contact from a fuse carrier. The first load conductor  54  is adaptable to provide different devices for receiving the carrier plug contact. In one preferred embodiment, fuse connector the clip  64  includes a number of bends or folds at the end of the conductor  54 , which create a U-shaped conductive insert for the carrier plug contact. The U-shaped fuse connector clip  64  is adaptable to be bent slightly past 180 degrees so that the walls of the U-shape spread apart upon insertion of the carrier plug contact. In this manner, the U-shaped fuse connector clip  64  press-fits onto the plug contact and removably holds the carrier in place.  
         [0041]    The housing  12  also includes a second conductive load device conductor  66 , which is also copper or copper alloy. In one preferred embodiment, the second load conductor  66  is suitably bent from one piece of metal to provide a desired shape and rigidity. One end of the second load conductor  66  terminates and defines a second load terminal  68 , which preferably defines an aperture. The operator electrically connects a second load wire  70  to the second load terminal  68  by compressing the second load wire  70 , or suitable connector attached thereto, between a screw  72  and a lockwasher and nut  74 . The second load terminal  68  is preferably vertically or horizontally disposed away from the first load terminal  56 , e.g. one inch (25.4 mm), such that the operator can readily access both terminals.  
         [0042]    The opposing end of the second load wire  70  terminates with an electrical connection to a second electrical or load device. The second load device also can have a fuse rating of between one and ninety amps. The second load wire  70  is appropriately sized thereto and is preferably an electrically insulated copper or copper alloy stranded wire. The second load device can have the same, slightly different or substantially different load current than the first device. The first and second load wires  58  and  70  can also run in parallel in the same circuit.  
         [0043]    The opposing end from the second load terminal  68  on the second load conductor  66  also defines a fuse connector clip  76  for removably holding a carrier plug contact. As above, the fuse connector or clip  76  preferably includes a number of bends or folds at the end of the conductor  66 , which create an overly bent U-shaped copper or copper alloy conductive insert for the fuse carrier plug contact. The U-shaped fuse connector or clip  76  also press-fits onto a fuse carrier plug contact and removably holds the carrier in place.  
         [0044]    The housing  12  further includes a conductor  78 , which is likewise copper or copper alloy. In one preferred embodiment, the conductor  78  is integrally formed with, fused to or otherwise fixed to and in electrical communication with the line conductor  44 . The ends of the conductor  78  define copper or copper alloy fuse connectors clips  80  and  82  for removably holding a fuse carrier plug contact. As above, the fuse connectors or clips  80  and  82  preferably include a number of bends or folds at the end of the conductor  78 , which create an overly bent U-shaped conductive insert for the fuse carrier plug contact. The fuse connectors or clips  80  and  82  likewise press-fit onto the carrier plug contact.  
         [0045]    It should be appreciated that the cavity defined by side walls  36  and the aperture  26  contains a pair of clips along the inner insulated wall  32  of the cavity. When the operator slides a fuse carrier into the aperture  26 , the plug contacts of the carrier eventually mate with the clip  64  of the first load device conductor  54  and the fuse connector or clip  80  of the conductor  78  (in electrical communication with the line conductor  44 ), respectively. Further, the cavity defined by side walls  36  and the aperture  28  contains a pair of clips along the inner insulated wall  32  of the cavity. When the operator slides a fuse carrier into the aperture  26 , the plug contacts of the carrier eventually mate with the clip  76  of the second load device conductor  66  and the fuse connector or clip  82  of the conductor  78 , respectively.  
         [0046]    A pair of blown fuse indicators  84  and  86  are mounted to the front wall  24  of the housing  12  via the apertures  30 . The indications provided by the blown fuse indicators  84  and  86  preferably emanate away from the front wall  24 , so an operator easily sees them. The present invention provides any type of blown fuse indicator currently known in the art. The blown fuse indicators  84  and  86  of the present invention are also adaptable to include separately fused alarm outputs, such as the springing or “grasshopper” type of alarm switch. In this instance, the disconnect  10  provides an alarm contact  88 , illustrated here disposed in the back wall  22   b . It has been observed, however, that such devices when installed separately from the fuse carriers can cause false alarms if the operator removes the fuse carrier, i.e., intentionally creating an alarm condition, without first disabling the alarm fuse.  
         [0047]    Consequently, the blown fuse indicators  84  and  86  in one preferred embodiment include indicators, such as light emitting diodes (LED&#39;s) but do not include an alarm switch. In an alternative embodiment (not illustrated), the removable fuse carriers are adaptable to include fused alarm switches, which close a contact that is in electrical communication with the alarm contact  88 . In this case, when the operator removes the fuse carrier, i.e., intentionally creating an alarm condition, the fused alarm comes with the carrier so that no false tripping occurs.  
         [0048]    The two LED&#39;s illustrated in FIG. 1 electrically communicate with the conductor  78 . That is, they electrically connect with the line side of the fused disconnect. Referring one to FIG. 2, a schematic electrical layout illustrates the line wire  50  connecting to the line conductor  44  and the load wires  58  and  70  connecting to the load device conductors  54  and  66 , respectively. The line side conductor  78  electrically communicates with the line conductor  44  and the LED indicators  84  and  86 . The fuse connectors or clips  64 ,  80 ,  82  and  76  receive the contact plugs of the fuse carriers. The load device, conductors  54  and  66  are alternatively adaptable to electrically communicate with the indicators  84  and  86 , and in one embodiment, the indicators are alternatively disposed on the load side of the fused disconnect  10 .  
         [0049]    Referring now to FIG. 3, one preferred fuse carrier  90  is illustrated. The fuse carrier  90  includes a preferably electrically insulative, flame retardant plastic housing  92 , which can be the same material as used for the housing  12  of disconnect  10 . The housing  92  defines a handle  94  and provides a slot in which a fuse  96  is removably inserted. The fuse electrically communicates with a pair of plug contacts  98  and  100 . The fuse  96  is rated anywhere from one to ninety Å. In another embodiment, the size of the housings  92  and/or the plug spacings can be different in the same disconnect housing. Preferably, the disconnect housing  12  is adapted to receive two fuse carriers  90  having the same sized housing  92  and the same plug contacts  98  and  100  having the same connection footprint.  
         [0050]    Referring now to FIG. 4, the disconnect  10  is illustrated with the fuse carriers  90  inserted into the cavities defined by the housing  12  of the disconnect  10 . The operator inserts the carriers  90  via the handles  94 . The carriers are oppositely inserted such that the plug contacts  98  of each carrier insert into or electrically communicate with the inside fuse connectors or clips  80  and  82  of the line side conductor  78 . The plug contacts  100  of the carriers  90  insert into or electrically communicate with the outside fuse connectors or clips  64  and  76  of the first load conductor  54  and the second load conductor  66 , respectively.  
         [0051]    It should be appreciated that with the fuse carriers  90  inserted into the disconnect  10 , a path of electrical communication exists between the line wire  50 , the line conductor  44 , the conductor  78 , the clip  80 , the plug contact  98 , the removable fuse  96 , the plug contact  100 , the clip  64 , the first load conductor  54  and the first load wire  58 . Removing the fuse carrier  90  from this path creates an interruption in electrical communication between the clips  64  and  80 . Likewise, a path of electrical communication exists between the line wire  50 , the line conductor  44 , the conductor  78 , the clip  82 , the plug contact  98 , the removable fuse  96 , the plug contact  100 , the clip  76 , the second load conductor  66  and the second load wire  70 . Removing the fuse carrier  90  from this path creates an interruption in electrical communication between the clips  76  and  82 .  
         [0052]    It should be understood that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. Such changes and modifications may be made without departing from the spirit and scope of the present invention and without diminishing its attendant advantages.