Patent Publication Number: US-9847198-B2

Title: Plug-in power contactor and system including the same

Description:
BACKGROUND 
     Field 
     The disclosed concept pertains generally to electrical switching apparatus and, more particularly, to electromagnetic switching devices, such as, for example, power contactors. The disclosed concept further pertains to systems including such power contactors. 
     Background Information 
     Electromagnetic switching devices, such as power contactors, are often used to electrically couple a power source to a load such as, for example and without limitation, an electrical motor or other suitable load. An electromagnetic switching device can include both fixed and movable electrical contacts as well as an electromagnetic coil. Upon energization of the electromagnetic coil, a movable contact engages a number of fixed contacts so as to electrically couple the power source to the load. When the electromagnetic coil is de-energized, the movable contact disengages from the number of fixed contacts thereby disconnecting the load from the power source. 
     Power contactors can include a plurality of inputs for a plurality of power sources and a plurality of outputs for a plurality of loads. The outputs can include normally open (NO) and/or normally closed (NC) outputs. Also, a number of NO and/or NC auxiliary switches can be provided that follow the state of the power contactor outputs. 
     Main power conductors can enter a power distribution panel through a power contactor, which is typically employed to open and close, thereby controlling power to the panel. Downstream of the power contactor in the panel is a circuit for sensing current. In a three-phase power panel, for example, downstream current transformers are employed for sensing the current, and upstream circuit breakers are employed for providing overcurrent, phase imbalance and/or ground fault protection. 
     There is room for improvement in power contactors. 
     There is also room for improvement in systems including power contactors. 
     SUMMARY 
     A power contactor that includes a number of inputs for a number of power sources, a number of outputs for a number of loads, a number of separable contacts for each pair of the number of inputs and the number of outputs, and an electromagnetic coil. The power contactor also includes a control circuit structured to control the electromagnetic coil to cause the number of separable contacts to open or close, a plurality of plug-in pins. Each of the plug-in pins is for a corresponding one of the number of inputs and the number of outputs, and is structured to plug into a backplane socket. The power contactor also includes an electrically insulating housing electrically insulating each of the plug-in pins from the other the plug-in pins. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A full understanding of the disclosed concept can be gained from the following description of the preferred embodiments when read in conjunction with the accompanying drawings in which: 
         FIG. 1  is an isometric view of a power contactor in accordance with embodiments of the disclosed concept. 
         FIG. 2  is an isometric view of a power contactor and three current sensors (shown in hidden line drawing) for a current sensing and protection circuit in accordance with another embodiment of the disclosed concept. 
         FIG. 3  is an isometric view of a power contactor and a single current sensor (shown in hidden line drawing) for a ground fault protection circuit in accordance with another embodiment of the disclosed concept. 
         FIG. 4A  is an isometric view of a printed circuit board including a socket that can accept the power contactor of  FIG. 2  or  FIG. 3 . 
         FIG. 4B  is an isometric view of a printed circuit board including a socket accepting the three current sensors of  FIG. 2 . 
         FIG. 4C  is an isometric view of a printed circuit board including a socket without a power contactor or a current sensor and being jumpered to a latching feeder connector in order to power a backplane. 
         FIG. 5  is an isometric view of a power contactor plugged-into the socket of the printed circuit board of  FIG. 4A . 
         FIG. 6  is an isometric view of the power contactor and the three current sensors of  FIG. 2  plugged-into the socket of  FIG. 5 . 
         FIG. 7  is a block diagram in schematic form of a system including the power contactor, the three current sensors and the current sensing and protection circuit of  FIG. 2  for sensing line current and/or phase imbalance in accordance with another embodiment of the disclosed concept. 
         FIG. 8  is a block diagram in schematic form including the power contactor, the single current sensor and the current sensing and protection circuit of  FIG. 3  for providing ground fault detection in accordance with another embodiment of the disclosed concept. 
         FIG. 9  is a block diagram in schematic form of a power contactor including a control circuit, a contactor coil, separable contacts, NO and NC outputs, and auxiliary contacts in accordance with another embodiment of the disclosed concept. 
         FIG. 10  is a simplified block diagram of a three-phase system including five of the power contactors of  FIG. 1 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     As employed herein, the term “number” shall mean one or an integer greater than one (i.e., a plurality). 
     As employed herein, the term “processor” shall mean a programmable analog and/or digital device that can store, retrieve, and process data; a computer; a workstation; a personal computer; a controller; a digital signal processor; a microprocessor; a microcontroller; a microcomputer; a central processing unit; a mainframe computer; a mini-computer; a server; a networked processor; or any suitable processing device or apparatus. 
     As employed herein, the statement that two or more parts are “connected” or “coupled” together shall mean that the parts are joined together either directly or joined through one or more intermediate parts. Further, as employed herein, the statement that two or more parts are “attached” shall mean that the parts are joined together directly. 
     The disclosed concept is described in association with a three-phase alternating current (AC) power contactor for aircraft applications, although the disclosed concept is applicable to a wide range of power contactors having any number of phases for any suitable AC or direct current (DC) power application. The power contactor will be described as being either a single throw or a double throw power contactor for input of one or two sets, respectively, of three AC phases and output of one set of three AC phases. Alternatively, it will be appreciated that the power contactor can be employed as a single throw or a double throw power contactor for input of one set of three AC phases and output of one or two sets, respectively, of three AC phases with normally open (NO) and/or normally closed (NC) outputs. 
     Referring to  FIG. 1 , a power contactor  2  includes three plug-in pins  4  for three separate AC power output lines (not shown) and six other plug-in pins  6 , 8  for AC power in (e.g., without limitation, a double throw power contactor including three NO inputs at pins  6  and three NC inputs at pins  8 ). In an alternative configuration, the three plug-in pins  4  can be employed for three separate AC power input lines (not shown) and the six other plug-in pins  6 , 8  for AC power out (e.g., without limitation, a double throw power contactor including three NO outputs at pins  6  and three NC outputs at pins  8 ). An electrically insulating housing  9  electrically insulates each of the plug-in pins  4 , 6 , 8  from each of the other plug-in pins. The housing  9  carries a 15-pin connector  12  for a power contactor coil control circuit  14  and houses auxiliary circuits  16  as will be discussed, below, in connection with  FIG. 9 . 
     As shown in  FIG. 2 , a molded piece  18  is added to the power contactor  2 . Alternatively, the molded piece  18  can mount as a standalone item to a backplane printed circuit board (PCB)  20  ( FIGS. 4A and 4B ). The example molded piece  18  encloses and electrically insulates three current sensors, such as example current transformers (CTs)  21  (shown in hidden line drawing). The molded piece  18  and CTs  21  can function as a circuit module and electrically connect (e.g., without limitation, the CTs have wires (not shown) to connectors (not shown) that couple to the backplane PCB  20 , or the CTs can have ridged pins (not shown) that plug into the backplane PCB  20 ) to the backplane PCB  20  ( FIGS. 4A and 4B ) in order to communicate with an external electrical load management system  22  ( FIG. 7 ) or with a self-contained on-board electrical load management system (not shown, but this may be part of the control circuit  14  of  FIG. 9 ). These components perform multiple functions and provide: (1) electrical isolation between the three pins  4  and the three example corresponding AC phases; (2) mounting of the power contactor  2  with the three CTs  21  ( FIGS. 2 and 5 ), mounting of the three CTs  21  without the power contactor  2  ( FIG. 4B ), or no power contactor  2  and no CTs  21  with a direct latching pin and socket latching connector  24  ( FIG. 5 ) by using the backplane PCB  20  with latching plug-in sockets  26  ( FIG. 4C ); and/or (3) mechanical positioning of a number of CTs (e.g., without limitation, three round CTs  21  for sensing line current and/or phase imbalance as shown in hidden line drawing in  FIG. 2 , or a single CT  28  for ground fault detection as shown in hidden line drawing in  FIG. 3 ). The three individual CTs  21  sense phase current and the external electrical load management system  22  ( FIG. 7 ) determines phase imbalance and/or overcurrent from the sensed three-phase currents. The single CT  28  senses the “summed current” (i.e., differential current, since the summed current is normally zero) of the three phases and compares that against a threshold for ground fault protection in the electrical load management system  30  ( FIG. 8 ). 
     In the example application, DC power (not shown) is separated from the AC power and enters and exits through other points of connection (not shown). For example and without limitation, the DC power could have additional openings in a sealed grommet (not shown, but see the sealed grommets  10  for three AC phase voltages of  FIG. 4A ) for a number of DC voltages (not shown). 
     In  FIGS. 2 and 3 , the six double throw pins  6 , 8  (shown in  FIG. 1 ) are under the molded piece  18  or  18 ′, respectively. The pins  6  and/or  8  of the power contactor  2  plug into a backplane socket  36  (e.g., the pins  6  plug into sockets  42  of the backplane socket  36  of  FIG. 4A ) that are part of the backplane PCB  20 . If the power contactor  2  is not populated ( FIG. 4C ), then jumpers  56  ( FIG. 4C ) are employed. For example, the three pins  4  are electrically connected to a number of branch circuit breakers  31  (shown in  FIGS. 7 and 8 ) which power loads (not shown) through two load connectors  32 , 34  as shown in  FIG. 5 . 
     In accordance with the disclosed concept, the power contactor  2  ( FIG. 1 ) employs the plug-in pins  4 , 6 , 8  for plugging into a backplane socket  36  ( FIGS. 4A and 5 ) of a circuit breaker module or main power distribution panel  38  ( FIG. 5 ). The plug-in pins  4  are either individually surrounded with the individual CTs  21  ( FIG. 2 ) or are all surrounded by the single CT  28  ( FIG. 3 ) for respectively sensing current and/or phase imbalance or for use in ground fault protection. There is also the example direct latching pin and socket latching connector  24  ( FIGS. 4A-4C and 5 ) on the backplane PCB  20  for line power conductors that are electrically connected to the backplane socket  36  for the power contactor  2 . 
       FIG. 4A  shows the backplane socket  36  mounted on the backplane PCB  20  with the molded piece  18  and including six exposed example sockets  40 , 42 . This permits the flexibility of installing the power contactor  2  ( FIG. 5 ) or not installing a power contactor (as shown in  FIG. 4C ). For example, panels (not shown) are often controlled by a master (not shown) with relatively smaller panels (not shown) being fed by relatively larger circuit breakers (not shown). In  FIG. 4A , three sockets  40  cooperate with either the three round CTs  21  ( FIGS. 2 and 4B ) of the molded piece  18  or with the single CT  28  ( FIG. 3 ) of the molded piece  18 ′. The three sockets  40  electrically engage the three power contactor pins  4  ( FIG. 1 ) and the three sockets  42  are for the power contactor NO pins  6  ( FIG. 1 ). The other three power contactor NC pins  8  ( FIG. 1 ) are not used in this example. The three sockets  42  for the pins  6  are also electrically connected to the example four-conductor direct latching pin and socket latching connector  24 , which is disclosed by U.S. Prov. Pat. Appl. Ser. No. 61/758,291, filed Jan. 30, 2013, which is incorporated by reference herein. This provides for the electrical connection of three lines and a ground (not shown) to the power contactor  2  and/or to the backplane PCB  20 . 
     As shown in  FIG. 5 , the example connector  24  includes a non-conductive block assembly  44 , a resilient wire support  46 , and four example conductor units  48 . The example connector  24  provides four electrical connections between a number of electrical devices (e.g., without limitation, a feeder (not shown) and the example power contactor  2 ). As shown, the connector  24  includes four example conductor units  48 . The connector  24  may include any suitable plurality of conductor units  48 . As shown in  FIG. 5 , the connector  24  is coupled to, and in electrical communication with, the backplane PCB  20 , which is coupled to, and in electrical communication with, other electrical components (not shown, but see the circuit breakers  31  of  FIGS. 7 and 8 ). Further, the connector  24  may be coupled to, and placed in electrical communication with, other electrical backplanes, electronics backplanes, or individual conductor pins/wires (not shown). Each of the conductor units  48  includes a suitable insulated conductor (not shown) from a power source (not shown), a pin (not shown) suitably crimped to the conductor (not shown) of the insulated conductor, and a socket (not shown) engaging the pin and being in electrical communication with the backplane PCB  20 . A clip member  50  includes four example clip passages (not shown) each of which engages and retains a corresponding terminal pin crimped portion (not shown) of a corresponding one of the conductor units  48 . 
     For example and without limitation, as shown in  FIGS. 4A and 5 , the direct latching pin and socket latching connector  24  for the power contactor  2  accepts line conductors (not shown) to power the backplane PCB  20  and/or the power contactor  2 , which is bolted into place on the backplane PCB  20  using the four example hex standoffs  52  and four screws or other suitable fasteners (not shown). The example power contactor  2  first plugs-in to the backplane socket  36  of the backplane PCB  20  and then it is held in place by the four screws or fasteners on the other side of the backplane PCB  20 . In the example application, due to the weight of the power contactor  2 , the screws are employed to retain the power contactor  2 . Alternatively, this can be accomplished with other suitable mechanisms for latching or locking in the power contactor. 
     As shown in  FIG. 4A , another 15-pin connector  54  connects to and accepts the corresponding 15-pin connector  12  of the power contactor  2  ( FIG. 1 ). 
       FIG. 4B  shows the backplane PCB  20  including the backplane socket  36  accepting the three CTs  21  (shown in hidden line drawing) for the current sensing and protection circuit of  FIG. 2  (not shown, but see, for example, the electrical load management system  22  of  FIG. 7 ). 
       FIG. 4C  shows the backplane PCB  20  including the backplane socket  36  without a power contactor or current sensor and being jumpered by three jumpers  56  for three AC phases to the direct latching pin and socket latching connector  24  in order to power the backplane PCB  20  from the connector  24  and through the socket  36 . 
     The current sensing ( FIG. 2 or 3 ) is modular with the power contactor  2  ( FIG. 5 ) or without a power contactor ( FIG. 4C ) since the molded pieces  18  or  18 ′ can optionally contain the respective CTs  21  or  28 . The power contactor  2  can be populated or not populated depending upon the application. The backplane power bus work (not shown) is set-up (e.g., without limitation, the power bus work is suitably jumpered at the corresponding backplane socket  36  without a power contactor present) ( FIG. 4C ) in order to power the panel with or without a power contactor. The individual and/or ground fault sensing CT options ( FIGS. 7 and 8 ) can optionally be not employed by simply not populating the corresponding CT(s)  21  or  28 . 
     As shown in  FIG. 5 , main power conductors (not shown) enter the power distribution panel or circuit breaker module  38  through the four example conductor units  48  each of which enters through a corresponding one of the sealed grommets  10  and employs latching pins (not shown) to feed power thereto with or without the power contactor  2 . The power distribution panel or circuit breaker module  38  employs embedded pins  4 , 6 , 8  ( FIG. 1 ) and sockets  40 , 42  ( FIG. 4A ) and greatly reduces the use of point-to-point wiring. The power contactor  2  is typically used for opening and closing power to the panel or the circuit breaker module  38 . In some embodiments, the power contactor  2  can also interrupt power to the panel or the circuit breaker module  38 . 
     Phase sensing and/or phase imbalance ( FIG. 7 ) and/or differential fault protection ( FIG. 8 ) can be provided by the power contactor  2  (e.g., in the control circuit  14  of  FIG. 9 ) or remotely in a master power center (not shown) or in the electrical load management system  22  ( FIG. 7 ) or  30  ( FIG. 8 ). In  FIG. 7 , the electrical load management system  22  includes a suitable processor, such as the example controller  60 , that outputs a contactor coil control signal  62  on lines X 1 ,X 2  and inputs current sense signals  64  (A),  66  (B),  68  (C) on lines S 1 ,S 2 ,S 3 , respectively. It will be appreciated that the lines X 1 ,X 2 ,S 1 ,S 2 ,S 3  can be part of the backplane PCB  20  of  FIG. 5 . The controller  60  can provide on/off control of the power contactor  2  as well as a number of protection routines (e.g., without limitation, overcurrent on individual phases A, B and/or C; phase imbalance on the three phases A, B and C). The three-phase power contactor  2  inputs power from the three phase lines A,B,C and outputs power to the three-phase circuit breaker (CB)  31 , which powers a number of three-phase loads (not shown). 
     In  FIG. 8 , the electrical load management system  30  includes a suitable processor, such as the example controller  70 , that outputs a contactor coil control signal  72  on lines X 1 ,X 2  and inputs a differential current sense signal  74  from the single CT  28 . The controller  70  can provide on/off control of the power contactor  2  as well as a number of protection routines (e.g., without limitation, ground fault protection). The three-phase power contactor  2  inputs power from the three phase lines A,B,C and outputs power to a three-phase circuit breaker (CB)  31 , which powers a number of three-phase loads (not shown). It will be appreciated that the lines X 1 ,X 2 ,S 1 ,S 2  can be part of the backplane PCB  20  of  FIG. 5 . 
     The backplane PCB  20  ( FIG. 5 ) preferably is a plug-in thermally conductive backplane. An example of such a structure for circuit breakers is disclosed by U.S. Pat. No. 8,094,436, which is incorporated by reference herein. The electrical bus structure  76  of the backplane PCB  20  can include a plurality of layers (not shown) that form a conductive power bus (not shown). Each of the layers can be sandwiched between two corresponding layers (not shown) of a thermally conductive thermoplastic. For example, one of the layers can be bonded to a corresponding one of the layers of the thermally conductive thermoplastic by an epoxy-based structural tape (not shown). For example, three different layers can be employed for a three-phase AC application. The example electrical bus structure  76  can employ, for example and without limitation, a relatively thin laser cut or stamped copper bussing for the layers. The example copper bussing can be sandwiched between the layers of the thermally conductive thermoplastic (e.g., without limitation, 0.060 in. thickness thermally conductive LCP thermoplastic). A same or similar backplane structure can be employed for the power contactor  2  and/or circuit breakers  31  (e.g., as shown in  FIGS. 7, 8 and 10 ). 
       FIG. 9  shows a power contactor  78 , which can be the same as or similar to the power contactor  2  of  FIG. 1 . The power contactor  78  includes a control circuit  14 , separable contacts  15 , a contactor coil  80 , outputs A 2 ,B 2 ,C 2  corresponding to the pins  4 , three-phase NO inputs A 1 ,B 1 ,C 1  corresponding to the pins  6 , three-phase NC inputs A 3 ,B 3 ,C 3  corresponding to the pins  8 , and the auxiliary circuits  16  including a plurality of auxiliary contacts  17 . Also shown is the example 15-pin connector  12 . 
       FIG. 10  shows an example three-phase system  82  (the three phases are shown as a single phase for simplicity of illustration; alternatively, any suitable number of phases can be employed) including five power contactors R 1 ,R 2 ,R 3 ,R 4 ,R 5 , which are the same as or similar to the power contactor  2  of  FIG. 1 . Power contactors R 2 -R 5  use the NO inputs (the pins  6  of  FIG. 1 ) while the power contactor R 1  uses the NC inputs (the pins  8  of  FIG. 1 ). Each of the power contactors R 1 -R 5  includes a corresponding closing coil  80  that is controlled by a control module  84  including a control interface connector  86 . Through the control interface connector  86 , commands can be provided to open or close any of the power contactors R 1 -R 5 . Also, system status, auxiliary contact states, power contactor states and/or current sensing information can be provided to an electrical management system (not shown). Optionally, the control module  84  can sense current at the output(s) of the circuit breaker(s)  88 , 90  and/or at the input  90  to an AC BUSS  92 . VFG (variable frequency generator)  94  and APU (auxiliary power unit)  96  are respective main and back-up AC sources that are selected by the power contactors R 1 -R 3 . The power contactor R 4 , when closed, powers a PDU (power distribution unit)  98  via an air turbine (RAM AIR) (not shown) and the power contactor R 5 , when closed, powers a cockpit circuit breaker panel  100 . This permits the use of multiple power sources (e.g., left and right main power generators in line with the respective left and right aircraft engines to provide rotational energy/power), multiple power contactors, such as for ground power and the APU  96 , and, in an emergency, ram air turbine power. 
     The disclosed concept can be used for the example circuit breaker module or main power distribution panel  38  with the power contactor  2 . Most applications have the power contactor  2  in an electrical load management system, such as the example three-phase system  82  of  FIG. 10 . For example, for a galley application, there are multiple panels daisy chained together, with a master panel having a galley load contactor. 
     The disclosed concept provides various benefits including: (1) volume reduction since the current sensing is modular and is either with the power contactor  2  or without a power contactor; (2) achieving simplicity since the power contactor  2  simply plugs into the backplane socket  36  of the example circuit breaker module or main power distribution panel  38 ; (3) the power contactor  2  and a number of current sensors (e.g., without limitation, CTs  21  or  28 ) are packaged together; and (4) the power contactor  2  can accommodate modular overcurrent, phase imbalance and/or ground fault protection, thereby eliminating the need for a number of upstream thermal and/or ground fault circuit breakers. 
     While specific embodiments of the disclosed concept have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of the disclosed concept which is to be given the full breadth of the claims appended and any and all equivalents thereof.