Abstract:
An electronic trip unit for a circuit breaker includes a programmed microprocessor and a module plug in removable signal communication with the microprocessor. The module plug includes a program identifier. The microprocessor recognizes the program identifier and accesses a program of a plurality of programs external to the module plug based on the program identifier. The microprocessor responds to the program to perform a function identified by the module plug. The function identifiable by the module plug includes a communications function, a load monitoring function, a non-tripping ground fault alarm function, a flag function, or any combination thereof.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application is a continuation-in-part application of U.S. application Ser. No. 09/682,512 filed Sep. 12, 2001, pending, which is hereby incorporated by reference in its entirety. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    Electronic trip units (trip units) for actuating the separable contacts in a circuit breaker are well known. An electronic trip unit typically comprises voltage and current sensors that provide analog signals indicative of current or voltage in a power distribution circuit. The analog signals are converted by an A/D (analog/digital) converter to digital signals that are processed by a microcontroller. The trip unit further includes RAM (random access memory), ROM (read only memory) and EEPROM (electronic erasable programmable read only memory) all of which interface with the microcontroller. The ROM includes trip unit application code, e.g., main functionality trip setting values, including initializing parameters, boot code, and operational parameters (e.g., trip setting instructions). Operational parameters for the application code are also stored in the EEPROM. An output of the electronic trip unit actuates a trip module, such as a solenoid, that trips a mechanical operating mechanism. The mechanical operating mechanism, in turn, separates a pair of main contacts within the circuit breaker. When the contacts open, circuit current is prevented from flowing from one contact to the other, and electrical current is prevented from flowing to a load that is connected to the breaker. The electronic trip unit initiates a trip for instantaneous, short time, long time, ground fault, and manual conditions.  
           [0003]    Circuit breakers having electronic trip units are described in U.S. Pat. No. 4,672,501 entitled “Circuit Breaker and Protective Relay Unit”. Such trip units often include a specific interface for a specific plug in module. One such example of a specific interface is a keypad along with a display for accessing the processor and for entering and changing the trip unit settings as described within U.S. Pat. No. 4,870,531 entitled “Circuit Breaker With Removable Display &amp; Keypad”. Other functional modules cannot be plugged into the place where this specific plug is received within the electronic trip unit. Thus, in order for the operator to receive additional functions for the trip unit, the operator would have to order the additional functions prior to the electronic trip unit being shipped to the operator. The operator could not install these additional functions in the field. Accordingly, it is desirable to have an advanced electronic trip unit that overcomes the drawbacks and deficiences of the prior art.  
         SUMMARY OF THE INVENTION  
         [0004]    In an embodiment, an electronic trip unit for a circuit breaker includes a programmed microprocessor and a module plug in removable signal communication with the microprocessor. The module plug includes a program identifier. The microprocessor recognizes the program identifier and accesses a program of a plurality of programs external to the module plug based on the program identifier. The microprocessor responds to the program to perform a function identified by the module plug. The function identifiable by the module plug includes a communications function, a load monitoring function, a non-tripping ground fault alarm function, a flag function, or any combination thereof.  
           [0005]    In another embodiment, a method for accessing and activating an accessory function of an electronic circuit breaker is disclosed. A key is entered into an electronic circuit breaker, which reads the key and compares the key against a predefined key set. In response thereto, access is unlocked to a preprogrammed set of instructions for driving an accessory function, and the preprogrammed set of instructions to drive the accessory function is activated.  
           [0006]    In a further embodiment, an apparatus includes a trip unit in removable signal communication with a module and a plurality of computer programs each when activated providing predetermined functionality to the trip unit. The trip unit is configured to receive from the module a program identifier associated with a plurality of programs. Receipt of the program identifier by the trip unit initiates the activation of the associated program, thereby providing predetermined functionality to the trip unit. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]    Referring to the exemplary drawings wherein like elements are numbered alike in the several Figures:  
         [0008]    [0008]FIG. 1 is a perspective view of a circuit breaker including an electronic trip unit with a module plug;  
         [0009]    [0009]FIG. 2 is the electronic trip unit with the module plug of FIG. 1;  
         [0010]    [0010]FIG. 3 is a schematic block diagram of the electronic trip unit with the module plug of FIG. 2 in the circuit breaker of FIG. 1;  
         [0011]    [0011]FIG. 4 is a flow chart providing an operation of the module plug and the electronic trip unit of FIG. 2;  
         [0012]    [0012]FIG. 5 is a flow chart providing an alternative operation of the module plug and electronic trip unit of FIG. 2;  
         [0013]    [0013]FIG. 6 is an isometric view of the module plug and electronic trip unit of FIG. 2; and  
         [0014]    [0014]FIG. 7 depicts exemplary module plugs in accordance with embodiments of the invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0015]    Referring to FIG. 1, a molded case circuit breaker  20  employing an electronic trip unit  22  is generally shown. Circuit breakers of this type have an insulated case  24  and a mid-cover  26  that house the components of circuit breaker  20 . A handle  28  extending through an aperture  30  of a cover  32  gives the operator the ability to turn circuit breaker  20  “on”, which allows electricity to flow through circuit breaker  20 , turn circuit breaker  20  “off”, which prevents electricity from flowing through circuit breaker  20 , or “reset” circuit breaker  20  after a fault. A plurality of electrically conducting load side contact straps (load straps)  40 ,  42 , and  44  at a load side  46  of circuit breaker  20  extend within case  24 . Line side contact straps  50 ,  52 ,  54  (shown on FIG. 3) are located on a line side  48  of circuit breaker and also extend within case  24 . Circuit breaker  20  illustrates a typical three-phase configuration, however, the present disclosure is not limited to this configuration but may be applied to other configurations, such as one, two or four phase circuit breakers. Removably disposed at electronic trip unit  22  is a module plug  60 , as will be described in further detail hereinafter. Electronic trip unit  22  also includes a cover  126  that has transparent windows  130  that enables the operator to view module plug  60  without removing cover  126 . Module plug  60  is flush with the face of electronic trip unit  22  so that cover  126  can be closed with module plug  60  in place in electronic trip unit  22 . Preferably, cover  126  has hinges  128  so that cover can be swung open and the operator may easily access module plug  60 . Cover  126  may also be locked to prevent tampering by unauthorized personnel.  
         [0016]    [0016]FIG. 2 illustrates electronic trip unit  22  removed from circuit breaker  20 . Electronic trip unit  22  includes a printed circuit board  61  to which a plug-in battery  62 , a plug-in rating plug  64 , and module plug  60  are removably mounted. Rating plug  64  allows the circuit interruption rating to be set by replacing rating plug  64  with a different rating plug. For instance, rating plug  64  may be used to set circuit breaker at 800 amperes maximum current. Rating plug  64  may be subsequently changed to set the maximum rating to 1200 amperes. Battery  62  supplies either a primary source or an alternative source of power to electronic trip unit  22 .  
         [0017]    Module plug  60  is a small electronic assembly, which may be approximately one inch square and approximately about one-half inch deep. Module plug  60  provides for an operator interface in the form of dials  66 , push buttons (not shown), rotary switches (not shown), and the like. Module plug  60  may also include an LCD or LED display  68  that provides the operator with information regarding circuit breaker  20  (shown in FIG. 1) (e.g., whether the circuit breaker is on, off, or tripped), or electronic trip unit  22  (e.g., the trip setting), or the power distribution circuit to which circuit breaker  20  (shown in FIG. 1) is connected (e.g., voltage, power, or current). Module plug  60 , battery  62 , and rating plug  64  each include a means for removably connecting to printed circuit board  61 . Such means includes a pin connector  69  (shown on FIG. 3), an input/output port (not shown), or the like.  
         [0018]    Referring to FIG. 3, a general schematic of a portion of circuit breaker  20  is shown. In circuit breaker  20 , load straps  40 ,  42 , and  44  are electrically connected to line straps  50 ,  52 , and  54  via electrical contacts  70 ,  72 ,  74 . Electrical contacts  70 ,  72 , and  74  are arranged so that each electrical contact  70 ,  72 , and  74  can be separated to stop the flow of electrical current from line straps  50 ,  52 , and  54  to load straps  40 ,  42 , and  44 . Electrical contacts  70 ,  72 , and  74  are mechanically connected to an operating mechanism  80 , which is a spring-loaded latching mechanism for separating contacts  70 ,  72 , and  74 . A trip actuator  82  is positioned to trip (unlatch) operating mechanism  80  in response to receiving an electrical trip signal from electronic trip unit  22  via line  84 . When operating mechanism  80  is tripped by trip actuator  82 , operating mechanism  80  separates each electrical contact  70 ,  72 , and  74  to stop the flow of electrical current from line straps  50 ,  52 , and  54  to load straps  40 ,  42 , and  44 . Line straps  50 ,  52 ,  54 , load straps  40 ,  42 ,  44 , and electrical contacts  70 ,  72 ,  74 , are collectively referred to as separable electrical paths, one path being arranged in each phase of circuit breaker  20 .  
         [0019]    Load straps  40 ,  42 , and  44  are configured for electrical connection to a three-phase power source exemplified by phases A, B, and C. Load straps  40 ,  42 , and  44  are coupled to current transformers  90 ,  92 ,  94 , respectively, which are then connected by lines  100 ,  102 , and  104  to a rectifier  106 . Rectifier  106  is electrically connected by line  108  to a microprocessor  110  mounted to printed circuit board  61  of electronic trip unit  22 .  
         [0020]    Electronic trip unit  22  includes microprocessor  110 , a random access memory (RAM)  112 , a read only memory (ROM)  114 , and a nonvolatile memory  115 . RAM  112  is coupled with microprocessor via a bus  117  and is used for the temporary storage of current and voltage data and as a scratch pad memory. ROM  115  is coupled with microprocessor via bus  117  and contains boot code data. Nonvolatile memory  115  is also coupled with microprocessor via bus  117  and stores a control program  116  that instructs microprocessor  110  to perform certain functions such as overcurrent protection, metering, protective relaying and communications. Nonvolatile memory  115  also stores a plurality of programs, or instructions,  120  that implement module plug  60  functions and a look-up table  121  that maps each program  120  with a corresponding module plug identification number. Microprocessor  110  controls RAM  112 , ROM  114 , nonvolatile memory  115 , and bus  117 .  
         [0021]    Electronic trip unit  22  is coupled with module plug  60  by pin connector  69 . Pin connector  69  is coupled with microprocessor  110  by a lead  122 . Module plug  60  includes an identification register  118 , dials  66 , and display  68 , all of which are coupled with pin connector  69  via lead  123 . Stored in identification register  118  is a binary representation of the module plug identification number unique to the type of module plug  60 . Rating plug  64  is also coupled with microprocessor  110  by a lead  124  and a pin connector  125 .  
         [0022]    Referring to FIGS. 3 and 4, module plug  60  and electronic trip unit  22  function as follows. Control program  116  instructs microprocessor  110  to perform a process  200 , which is started when microprocessor  110  is first booted up (block  202 ). An operator (not shown) plugs module plug  60  into pin connector  69 , which couples module plug  60  with microprocessor  110 . Control program  116  instructs microprocessor  110  to periodically read identification register  118  located at module plug  60  (block  204 ). Control program  116  determines whether a new identification number is present (block  206 ). If a new identification number is not present, control program  116  instructs microprocessor  110  to read identification register  118  (block  204 ). If a new identification number is present, then control program  116  instructs microprocessor  110  to compare the identification number read from identification register  118  with the identification numbers listed in look-up table  121  and determine the program  120  associated with the identification number (block  208 ). Control program  116  then instructs microprocessor to retrieve and execute the associated program  120  (block  210 ).  
         [0023]    Depending on which program  120  is accessed, program  120  will instruct microprocessor  110  to perform steps necessary to operate functions of module plug  60  (block  212 ). Such functions include accepting input from module plug  60 , such as reading input values from dials  66 , and providing output data to module plug  60 , such as providing signals to display  68 . Some examples of the functions module plug  60  can perform include displaying the current being measured by electronic trip unit  22 , changing the trip parameters stored in remote access memory  112 , displaying overload pick-up times, displaying instantaneous tripping values and energy values, and the like. When a specific module plug  60  is not desired, a blank module plug should be connected to electronic trip unit  22  to protect electronic trip unit  22 . In addition, microprocessor  110  reads the number associated with the blank module and determines that no additional function is required.  
         [0024]    Module plug  60  and electronic trip unit  22  provide the operator with a flexible electronic trip unit. The operator will be able to upgrade the electronic trip unit after purchasing the electronic trip unit. The operator will also be able to change the capability of the electronic trip unit easily by changing the module plug in the electronic trip unit. Thus, additional options and functions can be installed by the operator in the field.  
         [0025]    In an exemplary embodiment, microprocessor  110  is in operable communication with circuit breaker  20 , receiving informative signals from current transformers  90 ,  92 ,  94  and sending control signals to trip actuator  82 . Nonvolatile memory  115  includes a plurality of preprogrammed instructions  120  that are programmed into nonvolatile memory  115  at the point of manufacture of electronic trip unit  22 . The preprogrammed instructions  120  provide accessory functions that may be accessed and activated after a customer has purchased electronic trip unit  22  by the customer purchasing an appropriately programmed module plug  60 , which is releasably engaged with electronic trip unit  22 . Module plug  60  includes identification register  118  that contains an identification number that correlates with a designated preprogrammed instruction set  120  in nonvolatile memory  115 . Lookup table  121  includes a listing of preprogrammed identification numbers that correlate the identification number in identification register  118  with the appropriate preprogrammed instruction set  120 . Exemplary preprogrammed instructions  120  include, an ammeter display function, a ground fault function, an external communication function, a load monitoring function, a trip target flag, a load monitoring flag, a ground fault flag, a communications flag, and a blank function. Microprocessor  110  is programmed to read the identification number in identification register  118 , and if a new identification number is encountered, to retrieve and read the preprogrammed instructions that correlate to the new identification number. Upon reading the appropriate instructions, microprocessor  110  performs the steps necessary to operate the functions correlating to the identification number of module plug  60 . If no new identification number is encountered, microprocessor  110  performs the steps previously read in.  
         [0026]    As discussed above, an embodiment includes several preprogrammed instructions  120  at nonvolatile memory  115  that are accessible by a module plug  60  having a preprogrammed registration number. In an embodiment, the several preprogrammed instructions  120  are grouped according to function. A display module plug  60  is preprogrammed to access and activate preprogrammed instructions  120  to provide an ammeter display function.  
         [0027]    A quad module plug  60  is preprogrammed to access and activate preprogrammed instructions  120  to provide a ground fault function, an external communication function, and a load monitoring function. The ground fault function may be either a ground fault trip function, where circuit breaker  20  is instructed to trip on a ground fault condition, or a ground fault alarm function, where display  68  provides a visual alarm of a ground fault condition. The external communications function is provided by enabling a MODBUS communications port (not shown) on electronic trip unit  22 . The load monitoring function enables the user to view on display  68  when the highest of the three-phase currents has exceeded a predefined load threshold, the thresholds being settable through dials  66 . Dials  66  and display  68  provide an operator interface to module plug  60 .  
         [0028]    A flag module plug  60  is preprogrammed to access and activate preprogrammed instructions  120  to provide a trip target flag, a load monitoring flag, a ground fault flag, and a communications flag. The trip target flag enables the user to view on display  68  which trip target (source of trip activation, such as long-time (LT), short-time (ST), or instantaneous (Inst), for example) caused circuit breaker  20  to trip. The load monitoring flag enables the user to view on display  68  which phase has exceeded the predefined load threshold, and what the threshold setting is. The ground fault flag enables the user to view on display  68  whether a ground fault condition exists or not. The communications flag enables the user to veiw on display  68  when a communication action is occuring with electronic trip unit  22 .  
         [0029]    A blank module plug  60  is preprogrammed to prevent access and activation of any of the preprogrammed instructions  120  in nonvolatile memory  115 .  
         [0030]    As discussed above with reference to FIGS. 3 and 4, control program  116  instructs microprocessor  110  to perform process  220 , which is started when microprocessor  110  is first booted up  202 . With the insertion of a new module plug  60 , microprocessor  110 , under the control of control program  116 , identifies module plug  60  by reading the identification number at identification register  118 , compares this identification number with a plurality of preprogrammed numbers at look-up table  121  in nonvolatile memory  115 , determines from this comparison which of the preprogrammed instructions  120  correlate to the module plug identification number, retrieves and reads those instructions  120 , and then executes the associated instructions  120  to control either circuit breaker  20 , causing a trip action for example, electronic trip unit  22 , setting load monitoring thresholds for example, or module plug  60 , providing user displays for example.  
         [0031]    From the foregoing, it will be appreciated that module plug  60  does not contain any preprogrammed instructions  120 , containing instead only an identification number in identification register  118  that correlates, via lookup table  121 , with a set of preprogrammed instructions  120  in nonvolatile memory  115  at electronic trip unit  22 . All of the available accessory functions are preprogrammed, referred to as option dispensed in the industry, in electronic trip unit  22  at the time of manufacture, but are locked from access by control program  116 . To access and activate any one of the accessory functions, or preprogrammed instructions  120 , control program must recognize module plug  60  as being an authorized module plug and a match must be made between the identification number in module plug  60  with the list of identification numbers in lookup table  121 . In this manner, module plug  60  acts as the key that unlocks the desired accessory function, or preprogrammed instruction  120 , with lookup table  121  containing the preprogrammed key set that is used for key comparison.  
         [0032]    [0032]FIG. 5 depicts a general process  300  for using a lock and key approach for accessing and activating an accessory function  120  of electronic circuit breaker  20 . At  310 , a key, such as a module plug  60  having an identification register  118  containing an identification number, is inserted into an electronic trip unit  22  of an electronic circuit breaker  20 . At  320  and  330 , a control program  116  reads the key (module plug  60  having the identification number) and compares it against a set of predefined keys, such as a set of identification numbers preprogrammed into a lookup table  121  in a nonvolatile memory  115  at electronic trip unit  22 . At  340 , a control program  116  unlocks access to one of the preprogrammed set of instructions  120  only if the inserted key contains an identification number that matches one of the identification numbers of the predefined key set stored at lookup table  121 . Each preprogrammed identification number in lookup table  121  correlates to a preprogrammed set of instructions  120  in nonvolatile memory  115  that can be activated to drive an accessory function. At  360 , control program  116  instructs microprocessor  110  to activate the appropriate preprogrammed set of instructions  120  to drive the desired accessory function.  
         [0033]    [0033]FIG. 6 depicts an exemplary electronic trip unit  22  having a rating plug  64 , a plug-in battery (battery module)  62 , and a module plug  60 . The module plug  60  depicted in FIG. 6 is a display module plug  60  that provides an ammeter display function, however, as discussed above, other module plugs  60  are available and are depicted in FIG. 7. Referring now to FIG. 7, eleven exemplary module plugs  60  are depicted, with ten being functional and one being blank. The ten exemplary functional module plugs  60  provide ammeter display, ground fault, load shedding, and communication functions, as discussed above. The blank module plug  60  either instructs microprocessor  110  to disable access to preprogrammed instructions  120 , or provides a null signal to the same effect. It will be appreciated that while eleven exemplary module plugs  60  are depicted, other accessory functions may be accessed and activated as discussed herein without detracting from the scope of the invention.  
         [0034]    While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.