Patent Publication Number: US-2011057514-A1

Title: Power meter with transfer switch

Description:
BACKGROUND 
     Today more and more residential and commercial sites are employing some type of secondary, or back-up, power source to protect against utility power outages. When the secondary power source is installed, a transfer switch is also installed to provide a switchable connection between the utility power source and the load or the secondary power source and the load. The installation of the transfer switch typically involves installing a separate panel near a utility meter through which the utility power enters the building. 
     SUMMARY 
     An electric power control apparatus is provided that includes a meter enclosure defining a compartment and a display opening configured to fit a display associated with an electric power meter. The enclosure further defines a first entrance configured to allow passage of a primary conductor carrying electric power from a primary power source, a second entrance configured to allow passage of a secondary conductor carrying electric power from a secondary source, and an exit configured to allow passage of a load conductor carrying electric power to a load. An automatic transfer switch is mounted within the meter enclosure that is electrically connected to the primary conductor, the secondary conductor, and the load conductor to selectively provide a power flow path between the primary conductor and the load or the secondary conductor and the load. The automatic transfer switch includes a contactor set that selectively electrically connects the load conductor to either the primary conductor or the secondary conductor and a switching logic that senses power on the primary conductor and controls the contactor set to electrically connect the load conductor to either the primary conductor or the secondary conductor based on the sensed power on the primary conductor or the secondary conductor. 
     An electric power meter is disposed between the primary power source and the load and is mounted within the enclosure. The electric power meter includes a display that is fitted within the display opening. The meter is operable to measure an accumulated amount of power that has been provided on the primary conductor to the load and to display the accumulated amount of power on the display. 
     A primary power disconnect mechanism and/or a secondary power disconnect mechanism may be mounted within the meter enclosure. A status indicator may be disposed on an outer surface of the meter enclosure to communicate a present operating status of the electric power control apparatus. For example, the status indicator may communicate which of the primary conductor or secondary conductor is connected, via the automatic transfer switch, to the load conductor. 
     The transfer switch&#39;s switching logic may include a computer-readable medium storing computer executable switch actuation instructions and a microprocessor configured to read and execute the instructions. The switching logic may be configured to disconnect the primary conductor from the load conductor and to connect the secondary conductor to the load conductor when the sensed power on the primary conductor falls outside of a range of acceptable power quality. The switching logic may be configured to send a start signal to the secondary power source when the sensed power on the primary conductor falls outside of a range of acceptable power quality. The switching logic may be configured to disconnect the secondary conductor from the load conductor and to connect the primary conductor to the load conductor when the sensed power on the primary conductor falls within a range of acceptable power quality. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate various example systems, methods, and other example embodiments of various aspects of the invention. It will be appreciated that the illustrated element boundaries (e.g., boxes, groups of boxes, or other shapes) in the figures represent one example of the boundaries. One of ordinary skill in the art will appreciate that in some examples one element may be designed as multiple elements or that multiple elements may be designed as one element. In some examples, an element shown as an internal component of another element may be implemented as an external component and vice versa. Furthermore, elements may not be drawn to scale. 
         FIG. 1  is a schematic diagram of a prior art electric power control system. 
         FIG. 2  is a schematic diagram of an example embodiment of an electric power control apparatus. 
         FIG. 3  is a schematic diagram of an example embodiment of an electric power control apparatus. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG. 1 , a prior art electric power control system  10  is illustrated. The electric power control system controls power flowing to a load  60  on a load conductor  55  from either a utility power source (not shown) provided on a primary conductor  15  or a secondary power source  50  provided on a secondary conductor  45 . The electric power control system  10  includes an electric power meter  20  that meters the amount of power that has been supplied on the primary conductor  15  from a utility, a main disconnect  30  used to disconnect primary power from the load  60 , and a transfer switch mechanism  40 . The meter  20 , main disconnect  30 , and transfer switch  40  are separate from one another and require separate installation. 
     While example systems, methods, and so on have been illustrated by describing examples, and while the examples have been described in considerable detail, it is not the intention of the applicants to restrict or in any way limit the scope of the appended claims to such detail. It is, of course, not possible to describe every conceivable combination of components or methodologies for purposes of describing the systems, methods, and so on described herein. Therefore, the invention is not limited to the specific details, the representative apparatus, and illustrative examples shown and described. Thus, this application is intended to embrace alterations, modifications, and variations that fall within the scope of the appended claims. 
     To the extent that the term “includes” or “including” is employed in the detailed description or the claims, it is intended to be inclusive in a manner similar to the term “comprising” as that term is interpreted when employed as a transitional word in a claim. 
     Referring to  FIG. 2 , an electric power control system  70  is illustrated. The electric power control system  70  controls the flow of power from a primary power source such as, for example, a utility to a load  60 . The load  60  may be, for example, a main circuit breaker panel for a residence or building. Power from the primary source flows to the load  60  on a primary conductor  15  through an electric power control apparatus  70 . The electric power control apparatus  70  includes an electric power meter  74 , a primary breaker  76 , and an automatic transfer switch  78  all mounted and electrically connected to one another within a same enclosure  80 . The enclosure  80  defines an inner chamber in which the components are mounted as well as an opening for a meter display and the primary, secondary, and load conductors  15 ,  45 ,  55 . 
     The electric power meter  74  measures, accumulates, and displays an amount of power that has been supplied to the load on the primary conductor  15 . Power from the electric power meter  74  flows to the primary breaker  76 . The primary breaker  76  is used to manually disconnect the path from the primary power source to the load  60 . The primary breaker  76  may also automatically open in the event of power overload on the primary conductor  15 . 
     Within the enclosure  80 , the primary breaker  76  is electrically connected to an automatic transfer switch mechanism  78 . The automatic transfer switch includes an electrical contactor  79  that selectively connects either the primary power source or a secondary power source  50  to the load  60 . The transfer switch includes a control mechanism (shown in  FIG. 3 ), such as, for example, a microprocessor based controller to monitor the quality of the primary power. The control mechanism actuates the electrical contactor  79  to disconnect the load from the primary power source when the quality of the primary power is not satisfactory. A load conductor  55  routes power from the transfer switch to the load  60 . The secondary power source  50  is also electrically connected to the automatic transfer switch  78  by way of a secondary conductor  45 . The automatic transfer switch is operable to connect the secondary conductor  45  to the load conductor  55  when the primary conductor has been disconnected from the load conductor. The automatic transfer switch  78  thus connects either the primary power source or the secondary power source, but not both simultaneously, to the load  60 . 
     “Computer-readable medium”, as used herein, refers to a medium that stores signals, instructions and/or data. A computer-readable medium may take forms, including, but not limited to, non-volatile media, and volatile media. Non-volatile media may include, for example, optical disks, magnetic disks, and so on. Volatile media may include, for example, semiconductor memories, dynamic memory, and so on. Common forms of a computer-readable medium may include, but are not limited to, a floppy disk, a flexible disk, a hard disk, a magnetic tape, other magnetic medium, an ASIC, a CD, other optical medium, a RAM, a ROM, a memory chip or card, a memory stick, and other media from which a computer, a processor or other electronic device can read. 
     “Logic”, as used herein, includes but is not limited to hardware, firmware, software in execution on a machine, and/or combinations of each to perform a function(s) or an action(s), and/or to cause a function or action from another logic, method, and/or system. Logic may include a software controlled microprocessor, a discrete logic (e.g., ASIC), an analog circuit, a digital circuit, a programmed logic device, a memory device containing instructions, and so on. Logic may include one or more gates, combinations of gates, or other circuit components. Where multiple logical logics are described, it may be possible to incorporate the multiple logical logics into one physical logic. Similarly, where a single logical logic is described, it may be possible to distribute that single logical logic between multiple physical logics. 
     “Software”, as used herein, includes but is not limited to, one or more executable instruction that cause a computer, processor, or other electronic device to perform functions, actions and/or behave in a desired manner. “Software” does not refer to stored instructions being claimed as stored instructions per se (e.g., a program listing). The instructions may be embodied in various forms including routines, algorithms, modules, methods, threads, and/or programs including separate applications or code from dynamically linked libraries. 
       FIG. 3  is a more detailed schematic illustration of an electric power control apparatus  90  that functions in a similar manner to the electric power control apparatus  79  of  FIG. 2 . The electric power control apparatus  90  includes an enclosure  80  that houses the electrical components that are part of the apparatus. The enclosure defines a display opening  82  on a front face configured to fit a display on a utility meter. The enclosure  80  defines a first entrance  84  that allows passage of primary conductors  93 . In some embodiments, an alternate primary power conductor entrance  84 ′ is provided in addition to allow passage of primary conductors  93 ′. The two entrances  84  and  84 ′ may both be provided as knock out portions so that the enclosure may be adapted to receive primary power conductors from two different directions. The enclosure  80  also defines a second entrance  86  that allows passage of secondary conductors  100  and a load exit  88  that allows passage of load conductors  97 . In the illustrated embodiment, the enclosure includes two interior walls, a first wall  85  that defines a gutter that can accommodate the primary conductors  93 , and a second wall  87  that defines a compartment for the electric power meter  91  and primary conductors  93  or  93 ′. In the illustrated embodiment, a neutral connection module  95  is provided within the enclosure to provide a connection point for neutral conductors  95   a ,  95   b ,  95   c  associated with each of the primary conductors  93 , the secondary conductors  100 , and the load conductors  97 , respectively. The electric power meter  91  is electrically connected between the primary source and an automatic transfer switch  120  that will be described in more detail below. The electric power meter  91  includes a display (not shown) that is fitted within the display opening  82 . The automatic transfer switch  120  includes a switching logic  124  and a contactor  122 . The contactor  122  is configured to connect either the primary conductors  93  or the secondary conductors  100 , but not both simultaneously, to the load conductors  97 . The contactor  122  may be, for example, a relay or solid state device or any other suitable mechanism. The switching logic includes a microprocessor that is programmed to control the contactor  122  according to a control algorithm. The switching logic may thus be implemented as a circuit board that includes power and input conditioning components along with a processor and memory (or ASIC). 
     The switching logic  124  monitors the status of the primary power source as shown at  112  as well as the status of secondary power source as shown at  114 . The switching logic  124  controls the contactor  122  based on the status of these two inputs. For example, when the quality (such as a power level) of the primary power falls outside of a predetermined range, the switching logic actuates the contactor  122  to disconnect the load conductors  97  from the primary conductors  93  and to connect the load conductors  97  to the secondary conductors  100 . In some embodiments, when the switching logic  124  switches to the secondary power source, the switching logic  124  also provides a start signal as shown at  117  to the secondary power source. For example, this start signal  117  may cause a generator that is being used as a secondary power source to start up and begin supplying power. 
     The switching logic may continuously monitor the primary power source and actuate the contactor  122  to connect the primary conductors  93  to the load when the primary power source is supplying power at a level within a predetermined range of quality. The switching logic may also disconnect the secondary conductor from the load if it is detected that the secondary power source is providing power outside of a predetermined range. The switching logic  124  may also control a status indicator  126 , such as, for example, one or more LEDs, that communicates which of the primary or secondary source is presently connected to the load. 
     In some embodiments, the electric power control apparatus includes a primary breaker  94  and a secondary breaker  102  that can be manually operated to disconnect the primary conductors  93  and the secondary conductors  100 , respectively. The electric power control apparatus  90  can be installed by simply mounting the enclosure  80  to a building and connecting the primary conductors  93 , the secondary conductors  100  and the load conductors  97  to the electric power control apparatus  90 . 
     While example systems, methods, and so on have been illustrated by describing examples, and while the examples have been described in considerable detail, it is not the intention of the applicants to restrict or in any way limit the scope of the appended claims to such detail. It is, of course, not possible to describe every conceivable combination of components or methodologies for purposes of describing the systems, methods, and so on described herein. Therefore, the invention is not limited to the specific details, the representative apparatus, and illustrative examples shown and described. Thus, this application is intended to embrace alterations, modifications, and variations that fall within the scope of the appended claims.