Abstract:
A device for measuring gas temperature in a casing box having different heat-generating units disposed therein. The device includes a temperature-measuring arrangement disposed substantially in a plane above the different heat-generating units. The temperature-measuring arrangement includes a matrix of uniformly distributed temperature sensors configured to measure a temperature of rising gas.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a U.S. National Phase application under 35 U.S.C. §371 of International Application No. PCT/EP2007/003443, filed on Apr. 19, 2007 and claims benefit to German Patent Application No. DE 10 2006 019 578, filed on Apr. 27, 2006. The International Application was published in German on Nov. 8, 2007 as WO 2007/124871 under PCT Article 21 (2). 
     FIELD 
     The invention relates to a device for measuring temperature in a casing box, and particularly relates to a device for use in an electrical switchgear cabinet for low voltage. 
     BACKGROUND 
     Switchgear cabinets for low voltage typically have a frame composed of profiled bars which are terminated by walls which are connected to them, namely side walls, a rear wall, a top wall and a bottom wall. Situated inside the switchgear cabinet, which can be closed from the outside by means of a door, are with drawable parts which are on different planes and to which electrical units, for example control, switching and regulating units, are in turn applied. These units generate heat which heats the air or gas inside the switchgear cabinet, a thermal convection flow forming inside the switchgear cabinet. 
     In order to measure the air or gas temperature, a temperature-measuring sensor is situated on each withdrawable part, said sensor being fitted to the base in the upper region of the withdrawable part, to be precise where there is sufficient space for this sensor. This means that, when a unit which is arranged away from the temperature-measuring sensor—and there is optionally another unit between the unit in question and the temperature-measuring sensor—heats up to an impermissible extent, a change in the temperature of the first unit is detected by the temperature-measuring sensor only with a great delay. In this case, it is only determined that the temperature inside the switchgear cabinet has increased; this does not make it possible to detect which unit, if appropriate in which withdrawable part, has reached impermissibly high temperatures. 
     SUMMARY 
     An aspect of the present invention is to provide a device for measuring gas temperature in a casing box which makes it possible to accurately detect a unit which is generating impermissible temperatures. 
     In an embodiment, the present invention provides a device for measuring gas temperature in a casing box having different heat-generating units disposed therein. The device includes a temperature-measuring arrangement disposed substantially in a plane above the different heat-generating units. The temperature-measuring arrangement including a matrix of uniformly distributed temperature sensors configured to measure a temperature of rising gas. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Exemplary embodiments along with refinements of the invention will be described in more detail in the following with reference to the drawings, in which: 
         FIG. 1  shows a view into a withdrawable part used in a low-voltage switchgear cabinet; 
         FIG. 2  shows a cross section of a withdrawable part according to the invention in accordance with section line II-II shown in  FIG. 1 ; and 
         FIGS. 3 to 5  show three different exemplary embodiments of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     In an embodiment of the invention, a temperature-measuring arrangement is provided above the units approximately on one plane and has a plurality of temperature-measuring sensors which are arranged at uniformly distributed spaces arranged in the form of a matrix and are used to measure the temperatures of the rising air or the gas. 
     The invention utilizes the fact that the air heated by the units or the heated gas rises and a convection flow is thus produced inside the casing box. If the temperature-measuring sensors or temperature sensors are arranged above the units, the temperature sensors above that unit which has heated up to an impermissible extent can immediately detect the increased temperature; this avoids a time delay between the beginning of the impermissible heating of the unit in question and the response of the temperature sensor on account of gas or air mixing which is produced by convection inside the casing box and takes up a certain amount of time. 
     A carrier to which the temperature sensors are fitted can be provided in an advantageous manner. 
     In order to distribute the temperature sensors in a uniform manner, they are arranged on the carrier in the form of a mesh or grid. This results in a temperature-measuring sensor always being above each unit. 
     The temperature-measuring sensors may be in the form of thermosensors which are fastened to a carrier; the temperature-measuring sensors may also be in the form of resistance wires which have different resistance values, are arranged on one plane in the form of a mesh and are composed of a material whose resistance changes as the temperature changes. 
     The temperature-measuring arrangement having the individual temperature-measuring sensors or temperature sensors is a two-dimensional measuring arrangement which can be used wherever a plurality of units need to be monitored for increases in temperature. 
     As a result of the fact that the resistance wires are arranged in the form of a mesh, it is possible to determine the region in which the temperature rises excessively, with the result that a switching unit can be driven in a corresponding manner or an alarm device can be driven. 
     The device can be used in all types of casing boxes and anywhere in those spaces in which two-dimensional temperature detection is required and in which units which generate relatively high temperatures during faulty operation are accommodated. This may be the case, for example, in an electronic data processing device. 
       FIG. 1  illustrates a plan view of a withdrawable part  10  as can be used in a low-voltage switchgear cabinet. This withdrawable part has a bottom plate  11  as well as walls  12 ,  13 , which project perpendicularly at the edges of the bottom plate  11  and form the side walls, as well as walls  14  and  15 , the wall  14  of which forms the rear wall and the wall  15  of which forms the front wall to which a handle  16  is fitted. A plurality of electrical control, switching and regulating units  17 , through which, as electrical units, the current flows and which also generate heat in the process, are arranged on the bottom plate  11 . There is usually air in the switchgear cabinet in which the withdrawable part is situated, the switchgear cabinet being closed with respect to the ambient atmosphere, but not being encapsulated hermetically and in a gas-tight manner. 
     The effect of the electrical units on the atmosphere inside the switchgear cabinet results in convection, with the result that the heated air rises and produces a type of circulating flow inside the switchgear cabinet or, if appropriate, also inside the individual withdrawable part, depending on the configuration of the bottom plate  11 . 
     In order to measure the air temperatures produced in this case, other devices only include a temperature sensor  18  which, in the refinement according to the exemplary embodiment shown in  FIG. 1 , is arranged approximately in the center of the withdrawable part  10 . Temperature increases, for example in the switching unit or control unit  17  on the right, are detected by the temperature sensor  18  only after a certain delay time. 
     The arrangement of the temperature sensor  18  in the switchgear assemblies or withdrawable parts which are currently being produced and are in use is dependent on the space distribution inside the withdrawable part. 
     In  FIG. 3 , resistance wires  31 ,  32 ,  33 ,  34  and  35  which run at a distance from one another and parallel to one another and each have different resistance values are arranged on a carrier  30 . Further resistance wires which likewise run parallel to one another and at a distance from one another are arranged perpendicular to the resistance wires  31  to  35 . The resistance wires are connected to an evaluation device  50  by means of connecting lines  43  to  48 , only the connecting lines  43  to  48  from the resistance wires  36  to  42  to the evaluation device being illustrated here; the corresponding connecting lines between the resistance wires  31  to  35  and the evaluation device  50  are not illustrated for the sake of clarity. This temperature-measuring unit  51  is inserted into the withdrawable part  52  shown in  FIG. 2 , the withdrawable part  52  having strips  56  which run around on the insides of the walls  53 ,  54  and  55  and whose clear width is smaller than the outer circumference of the sensor arrangement  51 , with the result that the sensor arrangement or temperature-measuring unit  51  can be placed onto the circumferential strip  56 . 
     It goes without saying that the carrier  30  must have sufficiently large apertures, which are likewise not illustrated, so that the air heated by the electrical units  17  and  19  can flow past the resistance wires  31 ,  32 ,  33 ,  34 ,  35 . 
     In the embodiment shown in  FIG. 3 , the resistance wires  31 ,  32 ,  33 ,  34  and  35  run parallel to the front wall of the withdrawable part  10  and the other resistance wires  36  to  42  run perpendicular thereto, which entails advantages, as shall be explained in more detail further below. It goes without saying that it is also easily possible to arrange the resistance wires in such a manner that they run at an angle that is not equal to 90° to one another. This essentially depends on the arrangement of the units  17 ,  17   a  and  19  in the withdrawable part  10 . 
     It shall now be assumed that the electrical unit  17   a  depicted on the left in  FIG. 2  of the drawing heats up excessively. Since the unit  17   a  is under the resistance wire  37  and approximately under the resistance wire  33 , these two resistance wires are heated to a greater extent than the remaining resistance wires because the air heated by the unit  17   a  flows directly past said resistance wires. As a result, the resistances or resistance values of the two resistance wires  37  and  33  will change and the evaluation device  50  detects the region A, that is to say the region in which the resistance wires  37  and  33  cross, as a region of increased temperature and reports this to a superordinate central unit which then prompts further actions if required. 
       FIG. 3  shows an arrangement having a comparatively large number of resistance wires; the number of resistance wires depends on the size of the area to be covered and, if appropriate, on the number of electrical units inside the withdrawable part. It goes without saying that only two resistance wires or three resistance wires may also be respectively arranged in each direction. 
     The individual resistance wires are produced from a material whose resistance value changes as the temperature increases. In this case, all of the resistance wires may be produced from the same material or may be produced from different materials having different resistance values. 
       FIG. 4  shows an arrangement of three resistance wires which are composed of the same material and are arranged in the form of a small loop  55 , a medium loop  56  and a large loop  57 . In this case, on account of the wire length, the small loop has a resistance R 1 , the medium loop  56  has a resistance value R 2  and the large loop  57  has a resistance value R 3 . The loops  55  to  57  are arranged in such a manner that the loops are elongated rectangles, the sections  59 ,  60  and  61  of the loops  55  to  57  running above the withdrawable part, whereas the other sections  62  to  64  which run parallel to the sections  59  to  61  are laid in the region of one of the side walls of the withdrawable part. The sections  59 ,  60  and  61  run parallel to one another at the same distance, with the result that the three sections  59  to  61  are uniformly distributed over the withdrawable part. The sections  62 ,  63  and  64  may preferably run parallel to the front wall  15  of the withdrawable part. The ends of the loops  55 ,  56  and  57  are connected to an evaluation unit  58  in which the resistance values of the individual loops are detected. 
     In the arrangement illustrated in  FIG. 4 , only one line region, namely the line region under the sections  59  and/or  60  or  61 , can be monitored; it goes without saying that it is also possible to arrange an arrangement like that illustrated in  FIG. 4  in such a manner that the sections corresponding to the sections  59 ,  60  and  61  run perpendicular to the sections  59 ,  60  and  61 , as a result of which a structure in the form of a mesh or a grid like the structure illustrated in  FIG. 3  is likewise produced again. The ends of the loops of the second arrangement are likewise connected to the evaluation unit  58 . 
       FIG. 5  shows another refinement of the invention. Temperature sensors  74 ,  75  etc. are arranged on a carrier  70  in respective first rows  71 ,  72  and  73 , the temperature sensors  74  of the three rows  71  to  73  forming a row  76  which runs perpendicular thereto and runs parallel to further rows  77  which are formed by the temperature sensors  75  of the rows  71  to  73 . It goes without saying that the carrier  70  has openings which enable an essentially loss-free flow from the underlying electrical units to the thermosensors  74 ,  75 . 
     Instead of the arrangement of the temperature sensors  74 ,  75  as illustrated in  FIG. 5 , the temperature sensors may also be uniformly distributed above the withdrawable part  10  in another manner, as a result of which the end effect achieved is the same measuring effect as in the arrangement according to  FIG. 5  or the arrangements according to  FIGS. 3 and 4 . 
     In the arrangement according to  FIG. 5 , three first rows  71 ,  72  and  73  and five second rows  76 ,  77  which run perpendicular thereto (the three further rows are not provided with reference numerals) are provided; it goes without saying that it is also possible to increase or reduce the number of sensors depending on the size of the withdrawable part. 
     The invention is described with reference to a withdrawable part of an electrical low-voltage switchgear cabinet; the device for measuring gas or air temperature can be used wherever different heat-generating units whose temperature has to be measured and monitored are arranged. This may also be the case in an electronic data processing device; an embodiment in the form of a wire mesh as shown in  FIGS. 3 and 4  could be provided there, in particular. 
     The invention allows temperatures to be monitored and detected in a two-dimensional manner, the individual temperature sensors being arranged approximately on one plane. Accordingly, the invention can be used and applied anywhere in those spaces in which two-dimensional temperature detection is required and in which units which generate relatively high temperatures during faulty operation are accommodated. 
     The carrier may be a printed circuit board; and it is also possible to use a carrier film or to simply clamp the resistance wires to a frame.