Abstract:
A modular circuit breaker system includes a plurality of modules mounted side-by-side. The modules include electrical terminals for connection to live and neutral conductors of an electrical supply. Rigid metallic conductors extend between the modules for connecting electrical circuitry of one module to the electrical circuitry of the other module. Each conductor is removably engaged with electrical contacts mounted within the respective modules.

Description:
BACKGROUND OF THE INVENTION 
     THIS invention relates to a modular circuit breaker system comprising a plurality of inter-connectable modules, and to the modules themselves. 
     The use of conventional circuit breakers is increasingly being supplemented by specialised modules which can be mounted on a conventional mounting rail of an electrical distribution board. For example, earth leakage sensors, energy measurement modules and various other functional modules can be provided in miniature circuit breaker housings. 
     It is an object of the invention to provide a modular system which incorporates circuit breakers and other components. 
     SUMMARY OF THE INVENTION 
     According to the invention there is provided a modular circuit breaker system comprising at least first and second modules adapted for mounting side by side, at least one of the first and second modules including electrical terminals for connection to live and neutral conductors of an electrical supply; and at least one electrical conductor extending between the modules and arranged to connect electrical or electronic circuitry of one module to electrical or electronic circuitry of the other module. 
     Preferably, at least one of the modules includes a circuit breaker or other switching means. 
     Each module may comprise a housing adapted to be mounted on a rail or other mounting means adjacent to other modules. 
     In a preferred embodiment of the invention, each module has a housing with generally planar sides which abut the sides of adjacent modules in use, the at least one electrical conductor extending transversely through respective apertures in the abutting sides of adjacent modules. 
     The at least one electrical conductor preferably comprises a rigid metallic conductor connected removably to electrical contact means in each respective module. 
     In the preferred embodiment, the conductor comprises a threaded metal rod having a first end which can be screwed into a complementally threaded contact receptacle in a first module. 
     At least one second module preferably includes a contact defining an aperture through which a second end of the threaded rod can extend in use, the rod being maintained in electrical contact with the contact by a fastener screwed onto the second end of the rod. 
     For example, the contact may comprise a conductive pad having an aperture extending therethrough, the fastener comprising a nut bearing against the pad in use to connect the rod physically and electrically thereto. 
     The nut is preferably long enough to receive a first end of a further conductor, which can be screwed into the nut. 
     The system may comprises a plurality of different second modules connectable side by side in the above manner. 
     The system preferably includes a third module which serves to cover the exposed side of the last of the adjacent second modules. 
     The system may comprise a base module which includes a first communication circuit, and at least one further module comprising a second communication circuit, the first and second communication circuits communicating with one another in use via the at least one electrical conductor extending between the modules. 
     The base module may include a circuit breaker, and a control circuit operable to open at least one set of contacts of the circuit breaker. 
     The at least one further module may be arranged to transmit a switch signal to the base module, the control circuit of the base module being responsive to the trip signal to operate the circuit breaker. 
     In a typical embodiment, the system comprises first and second electrical conductors extending between the modules, the first conductor serving as a common or reference conductor and the second conductor serving as a signal conductor. 
     The invention includes a module for use in a modular circuit breaker system comprising at least first and second modules mounted side by side and wherein at least one of the first and second modules includes electrical terminals for connection to live and neutral conductors of an electrical supply, the module comprising a housing adapted to be mounted on a rail or other mounting means adjacent to at least one other module; an electrical or electronic circuit adapted for connection to an electrical or electronic circuit of said at least one other module; and electrical contact means for receiving at least one electrical conductor which connects the module to said at least one other module in use. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an exploded pictorial view showing a plurality of different modules according to the invention; 
     FIG. 2 is an exploded pictorial view of a portion of one of the modules of FIG. 1, showing how electrical conductors of the invention are connected thereto; 
     FIG. 3 is a pictorial view of the module of FIG. 2, showing an alternative method of connection of the conductors to the module; 
     FIG. 4 is a front view of a circuit breaker module of the invention with its cover removed; 
     FIG. 5 is a partial sectional side view of the module of FIG. 4; 
     FIG. 6 is a simplified block diagram of a modular system of the invention. 
    
    
     DESCRIPTION OF EMBODIMENTS 
     In FIG. 1, three different modules forming part of a modular circuit breaker system of the invention are shown adjacent a Minirail (trade mark) mounting rail  10 . 
     The first module  12  is a base or “start” module and comprises a moulded plastics housing containing an earth leakage circuit breaker with an operating handle  14  and a test button  16  on its front face. The housing of the module  12  is formed in front and rear halves  18  and  20  which are moulded from a plastics material having suitable mechanical and dielectric properties. The rear half  20  of the housing has formations  22  formed in it which engage clips  24  on the Minirail  10  in a known manner. 
     Adjacent to the first module  12  is a second, “intermediate” module  26  which has the same profile as that of the module  12 , viewed from the side, but which is one third its width and which is mounted on a single clip  24  of the rail  10 , instead of a pair of clips as in the case of the triple-width housing of the module  12 . The second module  26  has a housing which comprises left and right halves  28  and  30 , rather than front and rear halves  18  and  20  as in the case of the module  12 . 
     Both of the modules  12  and  26  have electrical terminals, i.e., line terminals  32  and load terminals  56  on their upper and lower surfaces, respectively. For example, in the case of the circuit breaker module  12 , its load terminals  56  are provided on the bottom surface of the housing, while its line terminals  32  are provided on the upper surface. 
     Both the modules  12  and  26  have substantially flat side surfaces  34  and  36 , respectively, allowing the modules to be mounted side by side on the mounting rail  10  with their adjacent side surfaces in abutment. 
     Instead of a Minirail mounting rail, a DIN mounting rail or another mounting means can be used to mount the modules within an enclosure. 
     Within the body of the module  12  are a pair of contact terminals which comprise threaded receptacles  58  and  60  connected to a control circuit  62  of the module  12  (see FIGS.  4  and  5 ). The respective receptacles are mounted adjacent to a pair of apertures  38  formed in the side surface  34  of the housing of the module  12  (see FIGS.  4  and  5 ), so that conductors in the form of threaded conductive rods  40  can be screwed into engagement with the receptacles through the apertures  38  (see FIG.  3 ). 
     The ends of the conductive rods  40  have diametral slots  42  formed therein, allowing the rods to be screwed into the receptacles  58  and  60  with the aid of a screwdriver. When this is done, the rods extend transversely from the side of the module  12 , in firm physical and electrical contact with the contact receptacles within the housing. 
     The control circuit  62  is constructed on a printed circuit board  64  and includes an input/output circuit which is able to receive signals from other modules  26  and to transmit signals to them, as well as a circuit which controls the operation of a shunt trip relay  74  arranged to cause tripping of the circuit breaker mechanism  66  of the module  12  on receipt of an appropriate control signal from a module  26 . 
     The terminal/receptacle  58  is connected electrically to the neutral line terminal  32  of the module  12  so that the conductor  40  connected to that terminal is referenced to the neutral of the mains electricity supply, while the conductor  40  connected to the terminal/receptacle  60  serves as a data conductor. In other applications, the terminals/receptacles may be isolated from the mains supply, depending on the application of the system. 
     The length of the rods  40  is chosen so that when the module  26  is in abutment with the module  12 , the rods screwed into the terminals/receptacles of the module  12  extend into through-bores  44  formed in the housing of the module  26 . As best seen in FIG. 2, the module  26  houses a circuit board  46  which has a pair of through-hole plated contact pads  48  formed on it. The contact pads  48  have central apertures  50  therein which extend through the circuit board and which are aligned with the bores  44 , so that the rods  40  extend through the apertures by a predetermined distance, typically two or three millimeters. 
     A pair of nuts  52  is provided, the nuts being formed from a length of metal tube threaded internally and provided with diametral slots  54  at one end thereof, allowing them to be screwed down snugly over the ends of the rods  40  until they bear against the contact pads  48 , thus securing the conductor rods  40  in firm physical and electrical contact with the pads  48 . The axial length of the nuts is chosen so that when they are securely in position over the ends of the rods  40 , approximately half the length of the nut at the slotted end thereof is free, allowing a further set of slotted conductive rods to be screwed into the open end. 
     In the above way, a desired number of intermediate modules  26  can be connected together electrically, effectively defining one or more conductive buses which extend the length of the installation and which allow the transmission of data or other electrical signals between the modules. For example, where the module  26  is a kilowatt hour meter, it can transmit a control signal to the control circuit  62  of the circuit breaker module  12  causing the latter module to open its contacts if the amount or rate of electricity consumption exceeds a predetermined value. 
     The control circuit  62  of the module  12  can send a status or confirmatory signal back along the data conductor to the relevant module  26 , so that the latter module can register that its control signal has been responded to. 
     The system includes a third module  76  which serves as an “end” or “cover” module and which is essentially a moulded plate which fits onto the exposed side of the last intermediate module  26 , preventing access to the electrical contacts in the side thereof. This is useful both for aesthetic, safety and fraud prevention reasons. 
     Apertures  68  are formed in the module  76  at the upper and lower edges thereof which are aligned with corresponding apertures  70  in the module  26 , allowing a security strap or wire to be passed through the holes and secured with a seal once the installation of the system has been completed. This provides an indication of tampering with the installation. 
     It will be appreciated that in some cases, only one transversely extending electrical conductor or bus may be required in a modular system, but two or more such busses can readily be provided. The described arrangement of the conductor components allows the various modules to be interconnected relatively quickly and easily, in a mechanically secure and reliable manner, without there being live electrical conductors exposed when not required. 
     Although it is likely that most installations of the invention will include a base module  12  containing a circuit breaker, it is possible that in some installations a circuit breaker is not required, and that only the intermediate modules  26  will be used. In this case, it is necessary to provide an anchor point for the conductor rods  40  in the first of the modules  26 . FIG. 3 shows how this is achieved, with relatively short screws  72  being used to secure the nuts  52  in place against the contact pads of the first module  26 , with additional conductor rods then being screwed into the nuts  52  as described above. 
     Alternatively, a version of the base module  12  can be provided which does not include a circuit breaker. For example, the base module could include a modem or other communication means, while an associated intermediate module could comprise a kWh meter. Such a combination may find use in a remote electricity metering system. 
     FIG. 6 shows, in a highly simplified schematic form, an example of a modular circuit breaker system of the invention. The system comprises a first module  80 , corresponding to the base module  12  in the above description, and a plurality of intermediate modules  82  to  88 . The modules  82  to  86  are a kilowatt hour meter, a latch module and a ripple control receiver, while the module  88  is designated “ETC” to signify that it can be any other desired module. The module  80  is an earth leakage circuit breaker (ELCB) unit and has live (L) and neutral (N) input and output terminals, with the respective live and neutral conductors passing through a toroidal core  90  of an earth leakage sensing circuit  92  and passing through a pair of contacts  94  controlled by the circuit  92 . 
     The electrical connections between the respective modules are identified as “COMMON” and “SLMS” (“single line messaging system”) respectively. The COMMON line which runs between the modules is connected to the neutral conductor in the module  80 , and provides a reference level in the communication system between the modules, while the SLMS line is a data or signal line on which data is transmitted between the modules. 
     The module  80  has a communication circuit  96 , while the modules  82  to  88  have essentially identical communication circuits  98 , the circuits  96  and  98  each being allocated an identity or address code so that the module  80  can identify which of the modules  82  to  88  is communicating with it, and vice versa. 
     The meter module  82  could be a conventional kWh meter or could be a more sophisticated pre-payment meter module. In the former case, the meter module may send a switch signal to the module  80  in the event that maximum load current exceeds a predetermined maximum threshold value, or over- or under-voltage conditions have been detected, for example. Alternatively, in the latter case, the pre-payment meter may send a switch signal both in response to an over current situation or when a pre-determined credit value stored in the meter has been used. In either case, the switch signal is transmitted on the SLMS conductor from the module  82  to the module  80  and is interpreted by the circuit  96 , which in turn provides an output to the control circuit  92  to cause it to open the contacts  94 . In the initial version of the system the switch signal comprised a 10 mA current signal having a duration of 30 ms. The use of current signals on the SLMS conductor is preferred, as these are relatively immune to noise and interference. 
     It will be appreciated that the communication scheme which is employed can be relatively simple, as described above, or can be more complex, depending on the requirements of the modules fitted. In some applications, a simpler scheme which does not support addressing may be sufficient. However, it is convenient that the described system permits communication between sophisticated electronic modules in a circuit breaker system utilising a relatively small number of robust electrical conductors.