Abstract:
A wire management method using a wire manager including current sensing features provides input for power measurement and management systems. The wire manager may be a single wire or single bundle retaining device with a current sensor such as a hall effect sensor integrated therein, or may be a multi-wire management housing with multiple current sensing devices disposed inside for measuring the current through multiple wires. The wires may be multiple branch circuits in a power distribution panel or raceway, and the wire manager may be adapted for mounting in such a panel or raceway. Voltage sensing may also be incorporated within the sensors by providing an electrically conductive plate, wire or other element that capacitively couples to the corresponding wire.

Description:
[0001]    The present U.S. patent application is a Continuation of U.S. patent application Ser. No. 13/024,199 filed on Jan. 9, 2011 and claims priority thereto under 35 U.S.C. §120. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention is related to wire managers for managing the position of one or multiple electrical wires, and more specifically to a wire manager including a current sensor that can be used to detect the current passing through a wire managed by the wire manager. 
         [0004]    2. Description of Related Art 
         [0005]    A need to measure power consumption in AC line powered systems is increasing due to a focus on energy efficiency for both commercial and residential locations. In order to measure power consumption of a circuit, the current drawn by the load must generally be measured, and for precise results, the characteristics of the load may also need to be known. 
         [0006]    Adding current sensors to a power distribution system occupies space and adds complexity, and if a large number of circuits must be measured, increased installation difficulties and may cause disarray in the power distribution system. 
         [0007]    Therefore, it would be desirable to provide a current sensing scheme that can provide isolated current draw information and optionally permit load characteristics to be taken into account, while providing organized and efficient installation with little additional space requirements for the power distribution system. 
       BRIEF SUMMARY OF THE INVENTION 
       [0008]    The invention is embodied in a wire management method using a wire manager that includes a sensor for sensing a current passing through a wire and its method of operation. The wire manager may be a single wire manager that manages the position of one or more wires at a single position and measures a net current passing through the wires, or the wire manager may have multiple securing mechanisms for securing multiple wires with corresponding current sensors located at each wire. A voltage sensor may be incorporated within the sensor(s) for sensing an electric potential of the wire(s). 
         [0009]    The wire manager may have a housing adapted for installation within a power distribution panel or raceway, and the securing mechanisms may be clamshell housings containing portions of a current sensor formed from a ferrite cylinder, which when closed around the wire, form either a complete ferrite cylinder, or one with a gap along the circumference in which a semiconductor magnetic field sensor may be inserted. The voltage sensor may be a cylindrical plate, a wire, a film, or other suitable conductive element for capacitively coupling to the wire in order to sense the electric potential of the wire. The voltage sensor may be located alongside the current sensing element, or within the current sensing element. 
         [0010]    The foregoing and other objectives, features, and advantages of the invention will be apparent from the following, more particular, description of the preferred embodiment of the invention, as illustrated in the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
         [0011]    The novel features believed characteristic of the invention are set forth in the appended claims. The invention itself, however, as well as a preferred mode of use, further objectives, and advantages thereof, will best be understood by reference to the following detailed description of the invention when read in conjunction with the accompanying Figures, wherein like reference numerals indicate like components, and: 
           [0012]      FIG. 1  is a pictorial diagram illustrating an electrical power distribution system including wire managers  10  according to an embodiment of the present invention. 
           [0013]      FIG. 2  is an illustration showing further details of wire manager  10 . 
           [0014]      FIG. 3  is another illustration showing further details of wire manager  10 . 
           [0015]      FIGS. 4A-4B  are illustrations showing details of sensor  20  in accordance with an embodiment of the present invention. 
           [0016]      FIG. 5  is an electrical block diagram illustrating circuits within wire manager  10  according to an embodiment of the present invention. 
           [0017]      FIGS. 6A-6D  are a pictorial diagrams depicting wire managers in accordance with alternative embodiments of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0018]    The present invention encompasses wire managers having current sensing, and optionally voltage sensing, features for providing input to power measurement systems. For example, the present invention can provide input to power monitoring equipment in computer server rooms, in which multiple branch circuit distribute power to various electronic chassis power supplies, and in which it is beneficial to provide power usage information for the various branch circuits to power monitoring and/or system control utilities within a computer operating environment. Other applications include power monitoring for commercial and/or residential energy management. 
         [0019]    Referring now to  FIG. 1 , a power distribution system in accordance with an embodiment of the present invention is shown. A power distribution panel  8  receives service entrance wiring  5  and distributes power to branch circuit wires  3  via circuit breakers  9 . Branch circuit wires  3  are routed to supply power to loads via conduits or other raceways  7 . Within power distribution panel  8 , wire managers  10 , in accordance with an embodiment of the invention, are installed. Wire managers  10  control the position of branch circuit wires  3  and further include sensing elements that are used to determine the current flowing through branch circuit wires  3  and optionally the magnitude and/or phase of the voltage on branch circuit wires  3  to provide for computation of the actual (complex) power delivered to the branch circuit loads. Wire managers  10  also include an interface/processing unit  12  that provides a wired or wireless interface to an external processing system and generally provides for computation of power usage-related information prior to transmission to the external processing system, although raw current (and optionally voltage) sensor output information could alternatively be transmitted, with computation of power usage-related information performed in the external processing system. Interface/processing unit  12  may alternatively be placed in locations and be dimensioned other than as shown. For example, interface/processing unit  12  may physically separate from wire manager  10  and be coupled to wire manager  10  by a wired, wireless, optical or other suitable interface. 
         [0020]    Referring now to  FIG. 2 , details of wire manager  10  of  FIG. 1  are shown. Branch circuit wires  3  are routed through a corresponding plurality of sensors  20  that provide at least an indication of a current flowing through the corresponding one of branch circuit wires  3 , and optionally the voltage or phase of the voltage at the corresponding one of branch circuit wires  3 . Details of sensors  20  will be described below in accordance with an exemplary embodiment of the invention, and further details of sensors  20 , along with other sensors that may alternatively be used to implement sensors  20  are described in above-incorporated U.S. patent application “NON-CONTACT CURRENT AND VOLTAGE SENSOR.” 
         [0021]    Referring now to  FIG. 3 , further details of wire manager  10  of  FIG. 1  are shown. Sensors  20  are fastened to a printed wiring board (PWB)  30 , that provides connections from each of current sensing elements  32  to interface/processing unit  12 , and also voltage sensing elements of sensors  20  if voltage sensing elements are provided. Interface/processing unit  12  includes integrated circuits  34  that implement power usage computations and information transmission, as well as signal processing to remove noise and properly scale the output(s) of sensors  20 . As illustrated, current sensing elements  32  extend through apertures in sensors  20  when sensors  20  are mounted to PWB  30 , and posts  38  may be provided to align and stabilize sensors  20  when sensors  20  are mounted to PWB  30  by mating posts  38  with recesses  36  in sensors  20 . Attachment of sensors  20  may be made by any appropriate means, but some degree of flexibility should be provided so that excessive force is not applied to the mechanical connection between sensors  20  and PWB  30  when branch wires  3  are moved, so that the mechanical connection is not damaged. A soft-setting adhesive, flexible posts  36  either thermo-welded or chemically bonded, or snap-connected may be used. Alternatively, or in addition to the above, the outer body of current sensing elements  32  may be made to provide mechanical attachment to sensors  20 . A cover  31  is provided to isolate circuits within wire manager  10  from the electrical circuits in the power distribution center or raceway in which wire manager  10  is installed. 
         [0022]    Referring now to  FIG. 4A , details of sensor  20  of  FIG. 3  are shown. A current sensing portion of sensor is formed by three ferrite pieces  24 A,  24 B that form a ferrite cylinder around one of branch circuit wires  3 , when sensor body  22  is closed. Top ferrite piece  24 A forms a half-cylinder, while ferrite pieces  24 B define a gap between ferrite pieces  24 B and in the circumference of the ferrite cylinder, in which current sensing element  32  of  FIG. 3 , which is generally a semiconductor magnetic field sensor, such as a Hall effect sensor, is disposed. An aperture  34  is formed through sensor body  22  for receiving current sensing element  32  as illustrated in  FIG. 3 . A voltage sensor formed by metal plates  28 A,  28 B provides capacitive coupling to branch circuit wire  3  that provides an AC waveform that is at least indicative of the phase of the voltage on branch circuit wire  3  and may be calibrated to provide an indication of the magnitude of the voltage if needed. Metal plate  28 A includes a contact  27  and metal plate  28 B includes a mating recess  29  to improve electrical contact between metal plates  28 A and  28 B, so that connection of one of metal plates  28 A and  28 B to the measurement system is needed to provide voltage sensing. A terminal  38  is provided on the bottom surface of sensor body  22  to provide an electrical connection from metal plate  28 B to a PWB. A latching mechanism  23  is provided so that sensor body  22  is held in a closed position after clamping the sensor body  22  around branch circuit wire  3 . A pair of recesses  36  may be provided for posts extending from a mounting surface, to stabilize and optionally snap-attach sensor body  22  to a PWB or other mounting surface. 
         [0023]    Referring now to  FIG. 5 , details of interface/processing unit  12  of  FIGS. 2  are shown. A multiplexer  101 A receives signals from the individual current sensing elements within sensors  20  and selects a sensor for measurement, providing input to a current measurement circuit  108 A, which is an analog circuit that appropriately scales and filters the current channel output of sensors  20 . The output of current measurement circuit  108 A is provided as an input to an analog-to-digital converter (ADC)  106 , which converts the current output waveform generated by current measurement circuit  108 A to sampled values provided to a central processing unit (CPU)  100  that performs power calculations in accordance with program instruction stored in a memory  104  coupled to CPU  104 . Alternatively, a separate current measurement circuit  108 A and multiplexer  101 A may not be necessary, and sensors  20  may be coupled directly to ADC  106 . The power usage by the branch circuit associated with a particular sensor can be determined by assuming that the branch circuit voltage is constant (e.g., 115Vrms) and that the phase relationship between the voltage and current is aligned (i.e., in-phase). However, while the assumption of constant voltage is generally sufficient, as properly designed distribution systems do not let the line voltage sag more than a small amount, e.g., &lt;3%, the phase relationship between voltage and current is dependent on the power factor of the load, and can vary widely and dynamically by load and over time. Therefore, it is generally desirable to at least know the phase relationship between the branch circuit voltage and current in order to accurately determine power usage by the branch circuit. 
         [0024]    When voltage measurement is implemented, another multiplexer  101 B is provided to receive signals from the individual voltage sensing elements in sensors  20  if voltage sensing is implemented. Multiplexer  101 B receives signals from the individual voltage sensing elements within sensors  20  and selects a sensor for measurement, providing input to a voltage measurement circuit  108 B, which is an analog circuit that appropriately scales and filters the voltage channel output of sensors  20 . A zero-crossing detector  109  may be used to provide phase-only information to a central processing unit  100  that performs power calculations, alternatively or in combination with providing an output of voltage measurement circuit to an input of ADC  106 . Alternatively, multiplexor  101 B may not be necessary and one or more voltage sensor outputs of sensors  20  may be connected directly to ADC  106 . In particular, it may not be necessary to make voltage measurements at each of sensors, for example, when sensing the phase of the voltage, a single measurement may suffice for providing a phase reference that is then used to determine the voltage-to-current phase difference for multiple branch circuits. Further, if multiple voltage measurements are taken, they voltage measurements may be used as an absolute voltage measurement, or the amplitude may be scaled to a known peak, r.m.s. or average value. An input/output (I/O) interface  102  provides either a wireless or wired connection to an external monitoring system, such as a wireless local area network (WLAN) connection  122 A or wired Ethernet connection  122 B. When power factor is not taken into account, the instantaneous power used by each branch circuit can be approximated as: 
         [0000]    
       
      
       P 
       BRANCH 
       V 
       rms 
       *I 
       meas  
      
     
         [0000]    where V rms  is a constant value, e.g. 115V and I meas  is a measured rms current value. Power value P BRANCH  may be integrated over time to yield the energy use. When the phase of the voltage is known, then the power may be computed more accurately as: 
         [0000]        P   BRANCH   =V   rms   *I   meas * cos (Φ)
 
         [0000]    where (Φ) is a difference in phase angle between the voltage and current waveforms. The output of zero-crossing detector  109  may be compared with the position of the zero crossings in the current waveform generated by current measurement circuit  108 A and the time ΔT between the zero crossings in the current and voltage used to generate phase difference Φ from the line frequency (assuming the line frequency is 60 Hz): 
         [0000]      Φ=2π*60*Δ T  
 
         [0000]    In general, the current waveform is not truly sinusoidal and the above approximation may not yield sufficiently accurate results. A more accurate method is to multiply current and voltage samples measured at a sampling rate much higher than the line frequency. The sampled values thus approximate instantaneous values of the current and voltage waveforms and the energy may be computed as: 
         [0000]      Σ(V n *I n )
 
         [0000]    A variety of arithmetic methods may be used to determine power, energy and phase relationships from the sampled current and voltage measurements. 
         [0025]    Referring now to  FIGS. 6A-6D , wire manager in accordance with other embodiments of the invention are shown. The wire manager of  FIG. 6A  includes a body portion  40 A that may be affixed to a chassis with a fastener, such as a sheet metal screw or an electrical wiring socket, or body portion  40 A may include an adhesive with a peel-off backing that may be removed from the underside of body portion  40 A and the wire manager pressed to a chassis or other location. A sensor  42  is integrated in body portion  40 A, and may be a single Hall effect device for measuring a net current through one or more wires secured by a wire-tie  44 A that passes through body portion  40 A, but may also include a voltage sensing element as in sensor  20  as described above. Interface wires  46  provide for connection of sensor  42  to a processing unit, which may receive input from multiple wire managers as shown in  FIGS. 6A-6D  in order to provide information about power usage by multiple power distribution branches in a manner similar to that employed in the power distribution system described above with reference to  FIG. 1 . 
         [0026]    The wire managers of  FIGS. 6B-6D  are similar to the wire manager of  FIG. 6A , so only differences between them will be described in further detail below. The wire manager of  FIG. 6B  includes a body portion  40 B that is affixed to a chassis with a fastener, such as a sheet metal screw and also accepts a wire tie  44 B for securing wires. Sensor  42  is positioned near an edge of body portion  40 B, in order to provide access to the mounting area. The wire manager of  FIG. 6C  has integral twist-type securing extensions  44 C that wrap around one or more wires, and sensor  42  is integrated adjacent to the union of securing extensions  44 C with body portion  40 C. The wire manager of  FIG. 6D  has an integral wire retaining strap formed as part of body portion  40 D. In each of the above-described wire managers, sensor  42  is position so that sensor  42  will be proximate wires that are retained by the wire manager is securing the wires. Ferrite or other magnetic material can be used to form a loop around the wire by integrating the magnetic material in the wire manager body in a manner similar to the integration of ferrite pieces  24 A,  24 B in sensor  20  described above. Also, insert bushings as described above can be used around wires to provide for more uniform wire distance when voltage sensing is employed within sensor  42 . The Hall effect sensors used in the above-described embodiments may be replaced by other current-sensing elements, with suitable changes to the sensor mechanical features. Examples of alternative current-sensing elements include current transformers. Rogowski coils, anisotropic magnetoresistance (AMR) elements, fluxgates, giant magnetoresistive (GMR) elements, fiberoptic current sensors, or any other non-contact current sensor. 
         [0027]    While the invention has been particularly shown and described with reference to the preferred embodiments thereof, it will be understood by those skilled in the art that the foregoing and other changes in form, and details may be made therein without departing from the spirit and scope of the invention.