Abstract:
In order to form an overcurrent switching apparatus for medium-voltage or high-voltage applications with a current detection device for changing over a contact system associated with them from a first state to a second state in the event of a threshold current being exceeded, the switching properties of which overcurrent switching apparatus are precise, an actuating device is disposed downstream of the current detection device, which is in a first current branch, via a coupling device. The actuating device is configured to change over the contact system, which is in a second current branch, from the first to the second state.

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention: 
     The invention relates to an overcurrent switching apparatus for medium-voltage or high-voltage applications having current detection means for switching a contact system, which is associated with them, from a first state to a second state when a threshold current is exceeded. 
     An electronics module having an overcurrent switching apparatus such as this is known from international patent application PCT/DE 2005/001147, which is regarded as prior art. In this prior overcurrent switching apparatus, a connecting conductor has a deformable section as current detection means. The deformable section is deformed when a threshold current is exceeded, such that a contact system is switched from a first state to a second state. The deformable section is in this case also used to form the contact system in that, together with a contact part, it forms the contact system. 
     BRIEF SUMMARY OF THE INVENTION 
     The object of the present invention is to design an overcurrent switching apparatus which can be designed flexibly and precisely as appropriate for the respectively stated requirements. 
     According to the invention, this object is achieved in that the current detection means which are located in a first current branch are followed via coupling means by operating means which are designed to switch the contact system, which is located in a second current branch, from the first state to the second state. 
     One major advantage of the overcurrent switching apparatus according to the invention is that the current detection means as well as the coupling and operating means in it represent assemblies and elements, respectively, in their own right, and can therefore be designed in their own right and can have appropriate dimensions; this also applies to the contact system, because this forms a system in its own right, on which the operating means act. This all allows precise adjustment and a wide adjustment range for the threshold current, in which the contact system can be switched from its first state to its second state. In this case, the contact system can advantageously be used in a flexible form to the extent that the first state of the contact system may be the open state and the second state may be the closed state of the contact system, or vice versa, such that an opening or a closing overcurrent switching apparatus is provided in a simple manner, depending on the respective requirements. This also results in the advantageous capability to carry out a switching process in the second current branch when an overcurrent occurs in the first current branch. 
     In one preferred embodiment, the current detection means comprise two busbar sections which run parallel to one another, in which the current is carried in opposite senses and of which at least one section can be deformed, wherein the deformable section can be changed from a normal position to an operating position by the threshold current being exceeded. In a refinement such as this, an electromagnetic force advantageously acts between the parallel-running conductors which carry currents in opposite senses, such that the deformable section is deformed by this force when a threshold current is exceeded, and is changed from a normal position to an operating position. In this case, the threshold current can easily and flexibly be adjusted via the deformation capability of the deformable section. 
     In a further refinement of the invention, the coupling means comprise a blocking element which is firmly connected to the deformable section. A blocking element such as this, for example a holding pin, is a simple option for coupling the current detection means to the operating means. 
     In one preferred embodiment, the operating means comprise an operating member which can be spring-loaded and is designed such that, when a blocking element is in the normal position of the deformable section, the operating member is held in a position with a stressed spring and is released in an operating position of the deformable section. An operating member such as this can be released in a simple manner by the blocking element, thus advantageously allowing the contact system to be switched quickly from its first state to its second state. 
     The operating member may be formed in various ways, for example as a plunger. In one particularly preferred refinement, the operating member is a moving carriage which can be stressed by means of the spring and has a rigidly connected guide rod. A carriage such as this can particularly advantageously be held or released by the blocking element. 
     In a further refinement, the contact system is formed from a moving contact which is rigidly connected to the operating means, in order to form a conductive connection between a first and a second opposing contact. The opposing contacts may in this case both be in the form of fixed contacts. If required, it may also be advantageous for one opposing contact to be in the form of a fixed contact and for the other opposing contact to be in the form of a flexible contact, in which case, for example, the flexible contact can be produced using a flexible connecting line. A contact system such as this can easily be switched from its first state to its second state by the operating means. 
     In another preferred embodiment, the current detection means comprise a coil which surrounds connecting conductors which carry the current. A coil allows an overcurrent to be detected in a precise manner since a current flowing in the connecting conductor in the coil induces a voltage by means of which the operating means can be operated in a simple manner. 
     In a further refinement of the invention, the contact system comprises an electrical switch which is connected to the coil via the coupling means and the operating means and which can be switched from the first state to the second state by a voltage induced in the coil when the threshold current is exceeded. An electrical switch advantageously has fast and precise adjustable switching characteristics in order to switch the contact system from the first state to the second state, with the switch being designed such that it remains in the second state, once it has been switched to this state. 
     In one expedient embodiment, the electrical switch is a thyristor. A thyristor is a precise electronic switching element as an electrical switch, which can easily be operated directly by the voltage induced in the coil. 
     In another embodiment, the electrical switch is an electromagnetically operated switch. An electromagnetically operated switch which is controlled by the coil allows precise and fast switching in a simple manner. 
     In a further refinement, the operating means comprise a control apparatus for the electrical switch. A control apparatus is advantageous for precise adjustment of the threshold current to be detected. 
     The invention also relates to a bridging apparatus for an electronics module, such as that disclosed in the prior international patent application PCT/DE 2005/001147 which was mentioned initially, and has the object of developing a bridging apparatus such as this for an electronics module such that it has a flexible design with a precise adjustable threshold current. 
     According to the invention, a bridging apparatus for an electronics module is used to achieve the object, having an overcurrent switching apparatus in one of the refinements described above, wherein the current detection means are designed to switch the contact system associated with them from a first state, in which the electronics module is connected to a circuit arrangement, to a second state, in which the electronics module is bridged in the circuit arrangement, when a threshold current is exceeded in the electronics module. This bridging apparatus advantageously allows a flexible design with a precise adjustable threshold current. The bridging apparatus therefore forms an advantageous application of the overcurrent switching apparatus according to the invention and can advantageously be used, for example, to bridge an electronics module according to German laid-open specification DE 101 03 031 A1. 
     In a further refinement, the contact system is conductively connected to connecting terminals of the electronics module. This ensures that the electronics module is bridged in a simple manner when the threshold current is exceeded, by provision of a conductive connection between the connecting terminals via the contact system. 
     In a further refinement of the invention, the current detection means detect the current in the electronics module. 
     The invention will be explained in more detail in the following text on the basis of the drawing and of exemplary embodiments, with reference to the attached figures, in which: 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
         FIG. 1  shows a schematic illustration of an overcurrent switching apparatus according to the invention, in a first refinement of a bridging apparatus according to a first embodiment; and 
         FIG. 2  shows a schematic illustration of an overcurrent switching apparatus according to the invention in a second refinement of a bridging apparatus according to a second embodiment. 
     
    
    
     DESCRIPTION OF THE INVENTION 
       FIG. 1  shows an overcurrent switching apparatus ÜS 1  of a bridging apparatus ÜB 1  in an electronics module  1  with connecting terminals  2  and  3 , which are connected via conductors  4  and  5  to a first opposing contact  6  and a second opposing contact  7  which, in the exemplary embodiment, are in the form of a first fixed contact  6  and a second fixed contact  7 , as well as to a circuit unit  8 . The circuit unit  8  comprises schematically illustrated electronic components  9 , for example a plurality of switching elements such as IGBTs, diodes and an intermediate-circuit capacitor of a converter, which are connected to one another via current detection means in the form of connecting conductors  10 ,  11  as well as further connections which are not illustrated in the figures (see the circuit unit in the German laid-open specification DE 101 03 031 A1 as mentioned above). In this case, the connecting conductors  10  and  11  are arranged in the circuit unit  8  such that any overcurrent which occurs in the event of a fault flows via these connecting conductors  10  and  11 . The connecting conductors  10  and  11  are in the form of busbars and are connected to one another at one end, so that a current flowing in the circuit unit  8  is passed via the busbars  10  and  11  in opposite senses. Coupling means  12  and  13  in the form of a holding pin  12  composed of an insulating material, as a blocking element  12 , are firmly connected to the busbar  11 , which is in the form of a deformable busbar, and the blocking element  12  extends through the busbar  10 , through a cutout  13  therein. The coupling means  12 ,  13  are followed, as operating means  14 ,  15  and  18 , by a moving carriage  14  which is blocked by the holding pin  12  and is prestressed by means of a spring  15  with respect to an insulating body  16  of the electronics module. A guide rod  18  of the carriage  14  extends through a cutout  17  in the insulating body  16 , at the end of which guide rod  18  a moving contact  19  is arranged which, together with the first fixed contact  6  and the second fixed contact  7 , forms a contact system  20 . 
     The state of the apparatus as illustrated in  FIG. 1  corresponds to the normal operating state of the electronics module  1  in which normal operating currents flow within the electronics module  1 . In the event of a fault, for example caused by a short-circuit within the electronics module  1  or a switching element being incorrectly operated, a considerably greater current can flow in the electronics module than the normal operating current, because of the discharging of the capacitor in the circuit unit  8 . Since the current is carried in opposite senses via the busbars  10  and  11 , electromagnetic interaction between them results in a force which forces the busbars  10  and  11  apart from one another and in the process deforms the deformable busbar  11  such that the holding pin  12 , which is firmly connected to the busbar  11 , is moved in the direction of the movement arrow A, and releases the carriage  14 . The force exerted by the spring  15  moves the carriage in the direction of the movement arrow B. In this case, the movement of the carriage  14  is guided by the guide rod  18  in the cutout  17  in the insulating body  16 , and is limited by the formation of a closed contact between the moving contact  19  and the fixed contacts  6  and  7 . A short-circuit current in the electronics module  1  therefore results in the contact system  20  being closed, as a result of which the remaining components in the electronics module  1  are bridged between the connecting terminals  2  and  3  of the electronics module  1  via the conductors  4  and  5  as well as the fixed contacts  6  and  7  and the moving contact  19 . Bridging of electronics modules in a circuit arrangement comprising a plurality of modules, for example in a series circuit, is particularly necessary when the functionality of the circuit arrangement is intended to be maintained in the event of failure of a single electronics module as a result of a malfunction. 
       FIG. 2  shows a further exemplary embodiment of an overcurrent switching apparatus ÜS 2  of a bridging apparatus ÜB 2  in an electronics module  21 . Connecting terminals  22  and  23  of the electronics module  21  are connected via conductors  24  and  25  to contacts  26  and  27  and to a circuit unit  28  with schematically illustrated electronic components  29 , for example switching elements which are not illustrated in the figures, such as IGBTs, capacitors and diodes. Connecting conductors  30  and  31  as well as further connections which are not illustrated in the figures are provided for connection of the components  29 . The connecting conductors  30  and  31  are in this case arranged in the circuit unit  28  such that an overcurrent occurring in the event of a fault flows via these connecting conductors  30  and  31 . The connecting conductors  30  and  31  are connected to one another at one end and, together with a coil  32 , form current detection means  30 ,  31 ,  32 . In this case, the coil  32  surrounds an area of the connecting conductors  30 ,  31 , and is coupled to operating means  36  and  37  via coupling means  33  and  34  in the form of connecting lines  33  and  34 . In the exemplary embodiment shown in  FIG. 2 , the operating means  36 ,  37  comprise a control apparatus  36  with a control connection  37  for controlling an electrical switch  38  which, together with the contacts  26  and  27 , forms the contact system  39 . 
     In the exemplary embodiment shown in  FIG. 2 , in the event of a failure of a semiconductor component, a short-circuit current that is produced by the capacitor in the circuit unit results in an induced voltage in the coil  32 , which is compared in the control apparatus  36  with a threshold value. If the induced voltage is above the threshold value, then the switch  38  is closed via the control connection  37 , such that the contact system  39  comprising the contacts  26 ,  27  and the switch  38  is closed, with the remaining elements of the electronics module  21  being bridged via the connecting terminals  22 ,  23  as well as the conductors  24 ,  25 . The switch  38  is in this case designed such that, after being switched to the second state, in the exemplary embodiment of the closed state, it remains in this state even when the induced voltage in the coil is no longer present, once the short-circuit current has decayed. Bridging of electronics modules in a circuit arrangement comprising a plurality of modules, for example a series circuit, is particularly necessary when the functionality of the series circuit is intended to be maintained in the event of failure of an individual electronics module as a result of a malfunction. The switch  38  may in this case be in the form of a thyristor or an electromagnet, in which case, depending on the desired precision, the drive may be provided either directly by means of the voltage induced in the coil  32 , or via the control apparatus  36  which, for example, may be in the form of a simple trigger circuit. 
     LIST OF REFERENCE SYMBOLS 
     
         
         ÜB 1 , ÜB 2  Bridging apparatuses 
         ÜS 1 , ÜS 2  Overcurrent switching apparatuses 
         Electronics module 
           2 ,  3  Connecting terminals 
           4 ,  5  Conductors 
           6  First fixed contact 
           7  Second fixed contact 
           8  Circuit unit 
           9  Electronic components 
           10 ,  11  Busbars 
           12  Holding pin 
           13  Bushing 
           14  Carriage 
           15  Spring 
           16  Insulating body 
           17  Bushing 
           18  Guide rod 
           19  Moving contact 
           20  Contact system 
           21  Electronics module 
           22 ,  23  Connecting terminals 
           24 ,  25  Conductors 
           26 ,  27  Contacts 
           28  Circuit unit 
           29  Components 
           30 ,  31  Connecting conductors 
           32  Coil 
           33 ,  34  Connecting lines 
           35  Electrical switching apparatus 
           36  Control apparatus 
           37  Control connection 
           38  Switching contact 
           39  Contact system 
         A, B Movement arrows