Abstract:
A gas diverter is disclosed that slows, cools, and directs the hot gas and plasma generated during the operation of an electrical switching device. The gas diverter mounts to the switching device and has an inlet for accepting the gas and exit for expelling the gas. The diverter has peripheral walls and internal partitions that divide the gas and provide for two independent circuitous flow paths. In multi-phase switching devices, a plurality of gas diverters may be used to further separate the gases generated in each respective phase. The gas diverter is made of a high temperature, arc resistant plastic which is molded to form a two piece structure. The gas diverter is mounted to the device via a slide in place flange-channel mechanism.

Description:
BACKGROUND 
   The present invention relates generally to the field of electrical contactors, circuit interrupters, circuit breakers, and similar devices. More particularly, the invention relates to a gas diverter used to slow, cool, and divert hot gas generated during the operation of electrical switching devices. 
   A variety of electrical switching devices are known and commercially available for establishing and interrupting current carrying paths between an electrical energy source and an electrical load. Electromechanical switchgear, for instance, is known for both single-phase and multiple-phase circuits. Such equipment generally includes an actuating assembly mechanically connected to a switch or contactor structure. In remotely-controllable switchgear of this type, it is commonplace to provide an electromagnetic actuating assembly which operates either on alternating current or direct current. The actuating assembly is energized by a control signal, such as from a remote controller. Electrical current through the actuating assembly causes movement of an armature under the influence of an electromagnetic field generated by an actuating coil. A carrier coupled to the armature, moves the movable contacts to either open or close the current-carrying path through the device. Depending upon whether the device is configured to be normally-open or normally-closed, the armature either separates the moveable contacts from the stationary contacts or brings the contacts together when the control signal is applied. 
   In industrial contactors of the type described above, the elements of the contact assembly may be subjected to a number of opening and closing cycles. During each operating cycle, arcs are produced between the movable contacts and the stationary contacts. In high power applications, the arcs produced generate a significant amount of electrical energy which is thereby converted into thermal energy. It is during this conversion process that the relatively non-conductive ambient atmosphere confined inside the switching device undergoes ionization and becomes a highly conductive hot gas and plasma. 
   The hot gas and plasma is generally permitted to escape from switchgear though splitter plates and holes in the device housing. Concerns in such situations include potential phase-to-phase short circuits in multi-phase devices, and the release of hot gases. The ionized gas that may exit the devices is generally conductive and could lead to short circuits if similar ionized gas exits from neighboring phase sections of the devices. The diffuse nature of the gas and plasma allow it to flow in a variety of directions providing for a vast number of possible short circuit paths. Certain devices include short dividers coupled to the outer surface of the housing intended to separate ionized and hot gases. However, these do not generally divert or cool the gas. 
   There is a need, therefore, for improved switching devices and structures associated with such devices. In particular, there is a need for improved techniques for directing and cooling hot gases and plasma created during opening or closing of contacts in such devices. 
   BRIEF DESCRIPTION 
   The present invention provides an improved gas handling arrangement designed to respond to such needs. The invention provides an innovative approach for slowing, cooling, and diverting high temperature gas and plasma generated by switching devices. The invention provides a gas diverter that mounts to the switching device and has an inlet for accepting gas and exit for expelling the gas. The gas diverter further has peripheral walls and internal partitions that provide a circuitous flow path that slows, cools, and diverts the gas before release. In one embodiment, the housing has two independent flow paths thereby increasing the control of the dynamics of the gas, resulting in an increase in the convection cooling efficiency. 
   In a multi-phase contactor, a plurality of gas diverters may be used to further separate the expelled gas, thereby greatly reducing the possibility of a phase-to-phase short circuit, while reducing the overall length profile of the switching device assembly. This allows for a reduction in the size of dividing panels or even eliminates the need for such panels altogether. 
   The gas diverter may be molded from a high temperature, arc resistant plastic, such as in a two piece structure, making it economical to manufacture. In one embodiment, the diverter incorporates a flange-channel structure that may be slid into a housing channel formed in the switching device, allowing it to be easy implemented into a switching device. 

   
     DRAWINGS 
     These and other features, aspects, and advantages of the present invention 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: 
       FIG. 1  is a perspective view of a three phase electrical switching device illustrating the location of exemplary gas diverters with respect to the switching device in accordance with certain aspects of the invention; 
       FIG. 2  is a exploded perspective view of the contacting section of the three phase switching device of  FIG. 1 , in which the actuating section has been removed to illustrate the contact housing, two terminals, two splitter plate assemblies, and two gas diverters; 
       FIG. 3  is an exploded perspective view of the gas diverter and terminal of  FIG. 2 ; illustrating the elements of the gas diverter in accordance with an exemplary embodiment; 
       FIG. 4  is an exploded perspective view of the gas diverter of  FIG. 3 ; shown from the perspective of line  4 - 4 , the terminal shown in  FIG. 3  having been removed; 
       FIG. 5  is a sectional view of the three phase switching device of  FIG. 1 , sectioned along line  5 - 5 , illustrating the relative location of the contacts, splitter plates, and gas diverter during the arc dissipation process; 
       FIG. 6  is a sectional view of the three phase switching device of  FIG. 1 , sectioned along line  6 - 6 , illustrating the gas flow path through the gas diverter assemblies and the resultant increased length of the phase-to-phase short circuit path. 
   

   DETAILED DESCRIPTION 
   Turning now to the drawings,  FIG. 1  illustrates an electrical switching device  10  in the form of a three-phase contactor for completing electrical current carrying paths for three separate phases  12  of electrical power. The switching device  10  includes an actuating section  14  and a contacting section  16  joined by fasteners  18 . The actuating section contains the electromagnetic operator that mechanically opens and closes current carrying paths through the device. The operation and relevant internal components of the device will be discussed in more detail below. In general, however, each phase section  12  has an input or line terminal  20  and output or load terminal  22 . Wire lugs  24  are secured to both the input and output terminals for receiving and completing an electrical connection with current-carrying wires or cables of a conventional design. Dividing panels or phase barriers  26  may be used to isolate vented gas from one phase from the neighboring phase. The phase barriers  26  are installed into slots  28  located in the contacting section  16 . As will be discussed below, the invention allows the dividing panels to be reduced in size or possibly even eliminated, thereby reducing the required space needed to implement the switching device. 
   A gas diverter  30  is located at each terminal for both the input side  20  and output side  22 . The gas diverter  30  slows, cools, and diverts the gas and plasma generated by the device before expelling it into the ambient environment, as discussed below. 
     FIG. 2  illustrates the contacting section  16  of the electrical switching device with the relevant parts of the contacting section exploded for explanatory purposes. The actuating section  14  (see  FIG. 1 ) has been removed for clarity. Only two of the six terminals, splitter plate assemblies, and gas diverters are illustrated in  FIG. 2 . The contact housing  32  has an external wall  34  and is divided into three sections  36  by internal partitions  38 . The partitions and walls serve to physically isolate the three phase sections from one another and the surrounding environment. The contact housing  32  has openings  40  in the exterior wall allowing the input and output terminals  20  and  22  to project outside of the housing. In the illustrated embodiment, the housing has channels  42  at each opening  40  configured to capture and orient the gas diverter  30  via a flange  44  extending from the diverter. 
   Each input terminal  20  and output terminal  22  has a bottom plate  46  used to mount the terminal to the contact housing  32 . A stationary contact pad  48  is located on the terminal and serves as the stationary contact point that allows electrical current to flow through the device. When the switching device is opened, a turnback  50  directs the resulting electrical arc to a splitter plate assembly  52 . The splitter plate assembly is configured with a plurality of splitter plates  54  that are stacked to allow the generated gas and plasma to flow therebetween. The gas and plasma enter the splitter plates on the entry side  56 , flow to the exit side  58 , and then into the gas diverter  30 . The splitter plate assembly has an exterior wall  60  that engages a lip  62  on the terminal, locating the splitter plates over the stationary contact assembly. 
   The gas diverter  30  and exemplary terminal  20  are illustrated in an exploded view in  FIG. 3 . The gas diverter  30  has two mating housing elements, a first housing or front element  64  and a second element or housing  66 . The front element  64  has an upper recess  68  and a lower recess  70 . The housing has upper and lower panels  72  and  74  that enter into and mate with these recesses. Once the elements are joined, the panels and the wall of element  64  form a single solid flange  44  that positions and orients the gas diverter in the contact housing  32  via the channels  42 . (See  FIG. 2 ). The simple and effective flange channel mechanism allows for quick and easy installation of the gas diverter. Those skilled in the art will appreciate that there are a number of different mounting arrangements that could be used as alternatives to the particular construction illustrated. Partitions  76  extend from the back side of the front element  64  and form part of the flow path when mated with the housing  66 , as described below. 
   In the view shown in  FIG. 4 , the terminal  20  has been removed and the gas diverter is viewed from the perspective of line  4 - 4  shown in  FIG. 3 . The opening  78  in the front element  64  serves as the gas inlet for the diverter  30 . The housing  66  has exterior walls  80  that contain the gas and plasma with a further raised section  82  that provides for a gas exit. When the front element  64  is mated with the housing  66 , the internal partitions  84  result in an upper flow path  86  and lower flow path  88 . While the current embodiment provides for two flow paths, those skilled in the art will appreciate that the number and configuration of partitions  76  and internal partitions  84  could be varied to provide for more than two flow paths. Certain of the partitions could also be removed or configured to provide a single flow path, or flow paths that are otherwise configured. 
   The housing  66  is provided with an arcuate indention  90  allowing it to interface with mating features  91  in the terminal  20 . The housing is not limited to this shape and can be configured to accommodate a number of different shapes and sizes. 
   In the current embodiment the housing elements are made from high temperature, arc resistant moldable plastic. Those skilled in the art will readily appreciate that the invention is not functionally limited to any specific material choices and any suitable material could be used for the housing elements. Furthermore, while the current design is a two piece assembly, alternative designs could include more than two pieces, or the diverter could be molded as a single piece, such as via the use of mold cores and so forth. 
     FIG. 5  is a partial sectional view of the switching device  10  from  FIG. 1 , sectioned along lines  5 - 5 , illustrating the switching device opening and thereby causing a break in the current flow path. The switching device is opened when an electromechanical operator attached to the movable contact assembly  92  is released, typically by de-energization of an operator coil, and mechanically separates the movable contact pad  96  from the stationary contact pad  48 , as indicated by reference numeral  94 . This in turns interrupts the electrical current from flowing through the device, as indicated by arrow  98 , and creates an electrical arc  100  between the two pads. 
   As discussed above, the arc produces significant heating through the release of electrical energy that is dissipated by the splitter plate assembly  52  as the arc is driven into the splitter plates. The turn back  50  and arc guide  102  typically direct the arc  104  to the splitter plates  54  magnetically, whereby the electrical energy is converted into thermal energy. Gases within the device may be ionized by the arc, creating plasma that is also driven towards the splitter plates. As a result of flow dynamics, the gas and plasma flow through the gaps  106  in the splitter plate assembly  52  and into either the upper  86  or lower section  88  of the gas diverter assembly  30  via the opening in the front element  64 . The gas is contained within the gas diverter  30  by the exterior walls  80  and is directed in a specific direction with respect to the terminal  20 . 
     FIG. 6  is a partial sectional view of the switching device  10  from  FIG. 1 , sectioned along lines  6 - 6 , illustrating one of the gas flow paths through the diverter  30  for each respective phase section  12 . The figure is exemplary of either the input side  20  or the output side  22  of the switching device  10  of  FIG. 1 . The figure illustrates three gas diverters  30  installed in the contact housing  32  via the flanges  44  and channels  42 . 
   As discussed above, the gas and plasma enter the diverter  30  at the inlet  108  via the opening  78  in the front element  64 . The partitions  76  extending from the front element  64  are interleaved with the internal partitions  84  contained in the housing  66  to form the flow paths  110 . The flow paths  110  confine and divert the hot gas and plasma through a circuitous path, thereby slowing and cooling them before expelling the gas at the exit  112 . The flow paths consist of generally parallel channels with  180  degree turnbacks on each respective end. Those skilled in the art will appreciate that a number of different configurations could be used to direct, divert and cool these gases and plasma. For example, a conical or spiral pattern or a variation of the parallel chambers could be used to create a number of different flow path configurations. Thus, the present invention is not functionally limited to any particular flow path arrangement. Furthermore, the gas flow for the current configuration is directed back towards the switching device  10  and thus away from possible temperature sensitive components and/or ignitable structures adjacent to the device. Those skilled in the art will appreciate that the flow may ultimately be directed back towards the switching device, or upwards, downwards, or away from the switching device. However, the illustrated embodiment enables released gas and any remaining plasma from each phase section to be effectively separated. Moreover, those skilled in the art will appreciate that the diverters achieve a very substantial effective length for cooling the gases and plasma, particularly as compared to known arrangement that simply release these into the immediate environment of the switching device. As noted above, in a present embodiment, flow paths are provided in upper and lower positions such that the flow of gas and plasma from the switching device is split between the upper and lower paths. Although not represented in  FIG. 6 , where provided, the upper flow path may be the same as, or as in a present embodiment, the opposite of the lower flow path. That is, while the lower flow path routes gas towards exit  112  on one side of the diverter, the upper flow path may route gas to an opposite side for venting. 
   Phase barriers  26  are shown in  FIG. 6  for illustrative purposes. Those skilled in the art will appreciate that the phase-to-phase short circuit path has been significantly increased via the invention, as compared with prior art arrangements. That is, in known arrangements employing dividing panels alone, the phase-to-phase short circuit path is simply the length around the dividing panel, as indicated by arrow  114 . Such arrangements, therefore, may require panels of substantial length. The gas diverter, on the other hand, creates a phase-to-phase short circuit path that is significantly increased and is a combination of the internal flow path  110  of the diverter plus the distance around the terminal  20  and phase barrier  26 , as indicated by reference numeral  116 . Depending upon the application, the significant increase in the short circuit path allows for the reduction in length of the dividing panels, or even their elimination altogether. As a result, the required space to implement the device and the overall length of the switching device package is reduced. 
   While only certain features of the invention have been illustrated and described herein, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.