Patent Publication Number: US-8526154-B2

Title: Current transformer assembly and electromechanical switching device

Description:
PRIORITY STATEMENT 
     This application is the national phase under 35 U.S.C. §371 of PCT International Application No. PCT/EP2009/052834 which has an International filing date of Mar. 11, 2009, which designates the United States of America, and which claims priority on German patent application number DE 10 2008 018 261.3 filed Apr. 1, 2008, the entire contents of each of which are hereby incorporated herein by reference. 
     BACKGROUND 
       FIG. 3  shows a known prior art reversing circuit  30  having a protective element (circuit breaker  33 ) and two switching elements (contactors  31 ,  32 ). The circuit breaker  33  has an integrated short-circuit tripping device (instantaneous n-release)  35  and an overload tripping device (delayed-action p-release)  37 . 
     The reversing circuit  30  is embodied for electrically connecting the phase inputs (L 1 , L 2 , L 3 ) to the phase outputs (T 1 , T 2 , T 3 ) with a direct phase sequence (L 1 →T 1 , L 2 →T 2 , L 3 →T 3 ) or with a modified phase sequence (L 1 →T 1 , L 2 →T 3 , L 3 →T 2 ). Furthermore, the phase inputs (L 1 , L 2 , L 3 ) can also be electrically isolated from the phase outputs by means of the reversing circuit  30 . In the case of the direct phase sequence an electric motor runs in a first direction, whereas in the case of the modified phase sequence it runs in the second direction. 
     As is well known, the reversing circuit  30  is controlled via the contactors  31 ,  32 . Only one contactor  31 ,  32  is activated in each case or both of the contactors  31 ,  32  remain deactivated. The wiring arrangement  34  upstream of the contactors  31 ,  32  and the reversing wiring arrangement downstream of the contactors  31 ,  32  are necessary for a reversing circuit. 
     The wiring arrangement  34  together with the reversing wiring arrangement  36  causes greater installation overhead and is prone to installation errors. 
     SUMMARY 
     At least one embodiment of the invention reduces the installation overhead and/or the susceptibility to faults or errors in the case of a reversing circuit. 
     At least one embodiment is directed to a current transformer assembly and/or an electromechanical switching device. 
     The dependent claims describe advantageous embodiment variants of the invention. 
     The wiring overhead can be reduced by way of a current transformer assembly having input terminals, output terminals, and current transformers which are placed between the input terminals and output terminals and to which at least one transformer output is electrically connected, and having an integrated wiring arrangement, wherein a number of input terminals are electrically connected to a number of output terminals via the integrated wiring arrangement in such a way that the wiring arrangement functions as a reversing wiring arrangement. 
     If the reversing wiring arrangement is embodied for electrically contacting three input terminals with a direct phase sequence and three input terminals with a modified phase sequence to the output terminals, the reversing wiring arrangement can be implemented in a simple manner by way of the transformer assembly. 
     If the input terminals are embodied as fixed contact makers of a switching element, the reversing circuit can be implemented in a compact design. 
     If the current transformer assembly additionally has integrated evaluation electronics, the latter being integrated on a printed circuit board for example, a compact, modular design is made possible. 
     The evaluation electronics can be connected in an elegant manner to at least one transformer output via a signal connection. Manufacturing tolerances can be better compensated for and a simple way/device of connection can be provided if the signal connection is implemented as a cable connection consisting of at least one male connector and a stranded wire conductor attached thereto, in particular if the male connector and the stranded wire conductor consist of flexible, electrically conductive material such as metal. 
     If the stranded wire conductor is fixed onto the printed circuit board by means of at least one solder point, contact failures can be avoided more effectively. 
     The wiring overhead can be reduced by way of an electromechanical switching device having a number of switching points which can be controlled by at least one associated electromechanical controller, and by way of a current transformer assembly, wherein the input terminals are electrically connected to the switching points. It is also possible to make the switching device more compact. 
     If the at least one electromechanical controller is embodied in the switching device for the purpose of controlling the switching points in two groups in such a way that the electromechanical switching device in each case contacts its phase inputs (L 1 , L 2 , L 3 ) in a direct phase sequence (L 1 →T 1 , L 2 →T 2 , L 3 →T 3 ) or in a modified (L 1 →T 1 , L 2 →T 3 , L 3 →T 2 ) phase sequence to the phase inputs (T 1 , T 2 , T 3 ), the switching device can completely take over the function of the reversing circuit. 
     If the input terminals are a constituent part of the switching points, the switching device can be made even more compact. 
     It is possible for the current transformer assembly to be used as a signal generator for the at least one electromechanical controller. In that case a protective function can be implemented for the switching device in a relatively simple manner. For example, protection against overload or short-circuit can be achieved if the at least one electromechanical controller is embodied for disconnecting the phase inputs (L 1 , L 2 , L 3 ) from the phase outputs (T 1 , T 2 , T 3 ) if at least one signal transmitted via the transformer output shows that the current flowing through the electromechanical switching device exceeds a permitted value. By this means the switching element can assume the functions of a protective element, with the result that a compact reversing circuit having a protective function or protective functions is realized. 
     If the permitted value is selectable, the electromechanical switching device can be used in a more versatile manner. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention is explained in more detail below with reference to example embodiment variants depicted in the attached drawings, in which: 
         FIG. 1  shows a current transformer assembly; 
         FIG. 2  shows a plan view of the current transformer assembly depicted in  FIG. 1 , with the top section of the housing removed; 
         FIG. 3  shows a reversing circuit; 
         FIG. 4  shows an electromechanical switching device; 
         FIG. 5  shows a circuit diagram of the electromechanical switching device depicted in  FIG. 4 ; 
         FIGS. 6 and 7  show two current transformer assemblies; 
         FIG. 8  shows a printed circuit board with a soldered-on stranded wire conductor for the signal connection; 
         FIG. 9  shows a fixing of the male connector in the housing of an electromechanical switching device; and 
         FIG. 10  shows a transformer assembly. 
     
    
    
     Corresponding structural elements are labeled with the same reference signs in all the drawings. 
     DETAILED DESCRIPTION OF THE EXAMPLE EMBODIMENTS 
       FIG. 1  shows a current transformer assembly  10 . The current transformer assembly  10  has input terminals  3 , output terminals  1 , and current transformers  2  which are placed between the input terminals  3  and output terminals  1 . The current transformers  2  are embodied for measuring the electric current flowing in an electrical conductor between an input terminal  3  and an output terminal  1  and can be toroidal core transformers, for example. 
     At least one transformer output  4  is electrically connected to each current transformer  2 . The output signals of the current transformers  2 , up to three current transformers, can be multiplexed. 
     The housing of the current transformer group  10  advantageously consists of a base section  8 , an intermediate section  7  and a top section  6 . 
       FIG. 2  shows a plan view of the current transformer assembly  10  depicted in  FIG. 1  with the top section  6  of the housing removed. 
     According to an example embodiment of the invention the current transformer assembly  10  has an integrated wiring arrangement  5 , such that a number of input terminals  3  are electrically connected to a number of output terminals  1  via the integrated wiring arrangement  5  in such a way that the integrated wiring arrangement  5  functions as a reversing wiring arrangement. 
       FIGS. 4 and 5  show how the current measurement is realized in the case of an electromechanical switching device  40  by way of one or more current transformers  2 . The transformer signals coming from the transformer output  4  of the transformer assembly  10  are transmitted to the printed circuit board  21  which contains the evaluation electronics  9 . The signal connection  56  is advantageously implemented by means of a cable connection, with the male connector establishing the electrical connection to the transformer assembly  10  and the stranded wire conductor  81  being fixed onto the printed circuit board  21  by way of a soldered joint. 
     The reversing wiring arrangement  5  is embodied for electrically contacting three input terminals  3  with a direct phase sequence (L 1 →T 1 , L 2 →T 2 , L 3 →T 3 ) and three input terminals  3  with a modified phase sequence (L 1 →T 1 , L 2 →T 3 , L 3 →T 2 ) to the output terminals  1 . 
     The current transformer assembly  10  is equipped with three current transformers  2 . It is, however, possible for the current transformer assembly  10  to be implemented with only one current transformer or two current transformers. 
     The input terminals  3  are embodied as fixed contact makers of a switching element. This is illustrated with reference to  FIGS. 4 and 5 . In this case the current transformer assembly  10  is connected in an electrically conductive manner to the electromechanical switching device  40 . In the example shown, the current transformer assembly  10  is integrated with the switching device  40 . 
     The electromechanical switching device  40  is provided with a number (three, six) of switching points  51  which can be controlled by at least one associated electromechanical controller  41 S,  42 S. The electromechanical switching device  40  additionally has a current transformer assembly  10 . The input terminals  3  are electrically connected to the switching points  51 . In order to make the design of the electromechanical switching device more compact, the input terminals  3  are in each case a constituent part of the corresponding switching points  51 , with the input terminals then being able to ensure the transmission of current from the moving contact makers of the switching point  51 . 
     The current transformer assembly  10  has integrated evaluation electronics  9  which can be integrated on a printed circuit board  21  (see  FIG. 8 ). The evaluation electronics  9  is connected via a signal connection  56  to the transformer output  4 , the signal connection  56  consisting of at least one male connector and a stranded wire conductor  81  attached thereto. The stranded wire conductor  81  is fixed onto the printed circuit board  21  by means of one or more solder points. 
     Owing to the flexibility of the stranded wire conductor  81 , mechanical shocks from the switching of the contactor drive unit of the electronic protection device  40  are more effectively avoided and tolerances of the components virtually completely compensated for. 
     The soldered connections on the printed circuit board  21  to the stranded wire conductor  81  help to avoid contact failures; installation advantages are also produced thanks to the flexibility of the stranded wire conductor  81 . An easy means of contacting the transformer signals via the male connector with stranded wire conductor  81  is also created. 
     The electromechanical controllers  41 S and  42 S are embodied for controlling the switching points  51  in two groups in such a way that the electromechanical switching device  40  in each case contacts its phase inputs (L 1 , L 2 , L 3 ) in a straight (L 1 →T 1 , L 2 →T 2 , L 3 →T 3 ) or in a modified (L 1 →T 1 , L 2 →T 3 , L 3 →T 2 ) phase sequence to the phase outputs (T 1 , T 2 , T 3 ). The electromechanical controllers  41 S,  42 S are, for example, solenoid actuators that can be controlled by analog or digital devices. 
     The current transformer assembly  10  is used as a signal generator for the electromechanical controllers  41 S,  42 S. 
     The electromechanical controllers  41 S,  42 S are embodied for disconnecting the phase inputs (L 1 , L 2 , L 3 ) from the phase outputs (T 1 , T 2 , T 3 ) if at least one signal transmitted via the transformer output  4  shows that the current flowing through the electromechanical switching device  40  exceeds a permitted value. The permitted value is advantageously selectable so that the overload protection function implemented by means of the transformer assembly  10  (cf. with the overload tripping device  37 ) can be set according to the load used (e.g. rated motor loading). 
     The contacting of the transformer assembly  10  is realized by way of a male/female (plug and socket) connector system on the printed circuit board  21  to the evaluation electronics  9 . The winding wire of the current transformers  2  is combined in the male connector and then plugged into the female socket. The female socket is connected to the printed circuit board  21  and the evaluation electronics  9 . 
     The signal connection  56  of the transformers  2  to the evaluation electronics  9 , the latter being fixed in this case on the printed circuit board  21 , is achieved by means of a cable connection. The cable connection consists of a male connector and a stranded wire conductor  81  attached thereto. The stranded wire conductor is fixed onto the printed circuit board  21  by way of a solder point. The male connector is plugged onto the transformer assembly  10  in order to tap the measurement signals, the connector being fixed in a between the housing  93  (magnetic chamber of the electromechanical switching device) and then contacted by the transformer assembly  10 . 
     By way of an embodiment of the invention, it is possible to implement optimal signal transmission in the case of an overall installation width of 90 mm of low-voltage switchgear (voltages up to 1000 volts) with reversing wiring arrangement. 
     The short-circuit protection function  35  can be integrated into the electromechanical protection device  40 . 
     Example embodiments being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the present invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.