Abstract:
A method and apparatus is disclosed for controlling the flow of electrical power. Specifically, there is provided an integrated electrical device that includes a mounting rail, a first contactor mounted on the mounting rail, a safety relay coupled to the first contactor; and a protective plate coupled to the safety relay. There is also provided a method of manufacturing an electrical device that includes coupling a first contactor to a mounting rail, coupling a safety relay coupled to the first contactor, and coupling a protective plate coupled to the safety relay to create the integrated electrical device.

Description:
BACKGROUND  
       [0001]     The present invention relates generally to systems for providing and controlling electrical power delivered to loads. More particularly, the invention relates to so-called “safety relays” and similar devices conventionally provided as separate, non-integrated components.  
         [0002]     Systems that distribute electrical power for residential, commercial, and industrial uses can be complex and widely divergent in design and operation. Electrical power generated at a power plant may be processed and distributed via substations, transformers, power lines, and so forth, prior to receipt by the end user. The end user may receive the power over a wide range of voltages, depending on availability, intended use, and other factors. In large commercial and industrial operations, the power may be supplied as three phase ac power (e.g., 208 to 690 volt ac, and higher). Power distribution and control equipment then conditions the power and applies it to loads, such as electric motors and other equipment. In one exemplary approach, collective assemblies of protective devices, control devices, switchgear, controllers, and so forth are located in enclosures, sometimes referred to as “motor control centers” or “MCCs.” Though the present techniques are discussed in the context of motor control, the techniques may apply to power management systems in general, such as switchboards, switchgear, panelboards, pull boxes, junction boxes, cabinets, other electrical enclosures, and distribution components.  
         [0003]     As most people are aware, electricity, especially at higher power levels, must be treated with care, with particular techniques being dictated by applicable professional and legal “codes”. For this reason, there is great interest in developing components, tools, and/or devices to safely channel the flow of electrical power to those places where it is needed, a load, for example. This is especially true in industrial applications, such as providing power to motors, manufacturing equipment, control systems and so forth. Code setting bodies include, for example, the Institute of Electrical and Electronics Engineers (IEEE). Such bodies set standards for equipment and methods, but often leave some latitude as to the particular implementation and design of compoents and systems that conform to the standards.  
         [0004]     Two devices that help to facilitate the management of electrical power are the contactor and the “safety relay”. Contactors are electrical devices that can be used to control the flow of electrical power. A typical contactor uses relatively low voltage control power (e.g., 24 volts dc, or 110 volts ac) to open or close contacts that control (i.e., complete a current-carrying path for) a higher voltage power (e.g., 480 volts). When a contactor allows power to flow through it, it is considered to be closed, and when the contactor does not allow power to flow through it, it is considered to be open. Generally, there are two types of contactors: normally open contactors and normally closed contactors. As will be appreciated by those skilled in the art, most such devices can be connected as normally open or normally closed, by properly terminating wiring to particular terminals associated with their movable contacts. A normally open contactor (if functioning properly) is in an open state when it is not energized (i.e., there is no control power being applied). When control power is applied to a normally open contactor, the contactor will energize, and close the switching contacts, which allows power to flow through the contactor. On the other hand, a normally closed contactor (if functioning properly) will be in a closed position when no control power is applied and in an open position when control power is applied to the contactor.  
         [0005]     As described above, a contactor facilitates the control of electricity by acting as a voltage control switch. For example, with a normally open contactor, load power (e.g., power for a motor) wired through the contactor may be turned on by applying the control power and turned off by removing control power. However, as most contactors employ physical electromechanical components, in certain circumstances, the physical components within the contactor can become fused in either the open position or the closed position (e.g., by “welding” of the movable and stationary contacts as a resulting of arcing). A contactor that is fused in the open position is unable to turn on; whereas a contactor fused in the closed position is unable to turn off. For a variety of reasons, either condition can result in an inability to operate the machinery as desired.  
         [0006]     One technique for mitigating such problems posed by fused contactors is to use so-called “safety relays”. Safety relays can monitor a condition, such as whether a contactor is actually in the open position or in the closed position and “relay” that condition information elsewhere in an electrical system. For example, if a safety relay is coupled to a normally open contactor, it can verify that the normally open contactor is open when there is no control power being applied and transmit this information to the power source or remote controller producing or providing the power controlled by the normally open contactor. In this way, safety relays may facilitate enhanced control and monitoring by enabling the operator or a control device to ensure that the contactor is operating properly before applying power to the contactor.  
         [0007]     As contactors and safety relays facilitate increased electrical control and monitoring, there is a need for improved systems and techniques for utilizing contactors and safety relays in electrical systems.  
       BRIEF DESCRIPTION  
       [0008]     The present invention provides novel devices and techniques for controlling the flow of power in an electrical system. More specifically, in one embodiment, there is provided an electrical device comprising a mounting rail, a first contactor mounted on the mounting rail, a safety relay coupled to the first contactor; and a protective plate coupled to the safety relay. The devices, techniques, and embodiments described herein can be used on single-phase and three-phase applications with little modification. Still further, the devices and techniques can be implemented in a stand-alone embodiment or in a distributed network environment.  
         [0009]     The integrated components greatly facilitate proper wiring and configuration of contactors and safety relays that were unattainable in conventional settings. Moreover, the integration of the components allows for factory control of the interoperability of the components, reducing or eliminating the need to field-wire the components, which can prove complex, challenging, time-consuming and expensive when conventional components are provided separately.  
     
    
     DRAWINGS  
       [0010]     These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:  
         [0011]      FIG. 1  is a diagrammatical perspective view of an integrated safety starter in accordance with aspects of the present technique;  
         [0012]      FIG. 2  is a diagrammatical view of a system employing the integrated safety starter, as illustrated in  FIG. 1 , in accordance with aspects of the present technique;  
         [0013]      FIG. 3  is a diagrammatical view of a system employing a network capable integrated safety starter in accordance with aspect of the present technique; and  
         [0014]      FIG. 4  is a block diagram of a networked motor control system employing the network capable integrated safety starter, as illustrated in  FIG. 3 , in accordance with aspects of the present technique. 
     
    
     DETAILED DESCRIPTION  
       [0015]     Turning now to the drawings, and referring first to  FIG. 1 , an integrated safety starter is illustrated diagrammatically and generally designated by a reference numeral  10 . The integrated safety starter  10  includes contactors  12   a  and  12   b . The contactors  12   a  and  12   b  are electrical devices that can be used to control the flow of power. In one embodiment, the contactors  12   a  and  12   b  are 100-C, four pole contactors available commercially from Rockwell Automation of Milwaukee, Wis. under the commercial designation 100-C.  
         [0016]     As described above, when a contactor allows power to flow through it, it is considered to be closed, and when the contactor does not allow power to flow through it, it is considered to be open. Generally, contactors may be wired as normally open and normally closed. A normally open contactor (if functioning properly) is in an open state when it is not energized (i.e., there is no control power applied to it). When control power is applied to a normally open contactor, the contactor will energize, and close the switch (i.e., physically join movable and stationary contacts), which allows power to flow through the contactor. On the other hand, a normally closed contactor (if functioning properly) will be in a closed position when no control power is applied and in an open position when control power is applied to the contactor. In one embodiment, the contactor  12   a  is a normally open contactor and the contactor  12   b  is a normally closed contactor.  
         [0017]     The integrated safety starter  10  may also include a safety relay  14 . The safety relay  14  may be configured to monitor a condition, such as whether the contactors  12   a  and  12   b  are actually in their open position or in their closed position, as appropriate, and to “relay” that condition information elsewhere in an electrical system  30  (see  FIG. 2 ). In a present embodiment, the safety relay  14  is a model commercially available from Rockwell Automation of Milwaukee, Wis. under the commercial designation Minotaur 138DP.  
         [0018]     As illustrated in  FIG. 1 , the contactors  12   a  and  12   b , and the safety relay  14  may be mounted on a mounting rail  16 . The mounting rail  16  may be any mounting rail suitable for mounting the contactors  12   a  and  12   b  and the safety relay  14 . For example, the mounting rail  16  may be a DIN rail. In one embodiment, the mounting rail  16  is a 45 millimeter (“mm”) DIN rail. In various embodiments, the mounting rail  16  may be configured to be attachable to an electrical assembly. For example, in one embodiment, the mounting rail  16  may be configured to snap or be screwed or bolted into a motor control center (“MCC”). In addition, in one embodiment, the contactors  12   a  and  12   b  and the safety relay  14  may also be configured to snap onto the mounting rail  16  for ease of assembly and removal.  
         [0019]     Moreover, the mounting rail  16  may also support one or more wires (not shown) and/or electrical connectors or terminal elements. For example, the mounting rail  16  may support connectors  17   a  and  17   b  that may be coupled to wires or traces that interconnect the connectors  17   a  and  17   b  to the contactors  12   a  and  12   b  and/or the safety relay  14 . In one embodiment, the connector  17   a  is configured to be coupled to a power supply (i.e., the upstream side of an electrical enclosure) and the connector  17   b  is configured to be coupled to the load side (i.e., the downstream side of an electrical enclosure) with wires interconnecting the connectors  17   a  and  17   b , the contactors  12   a  and  12   b , and safety relay  14 , as will be described in greater detail in regard to  FIG. 2 .  
         [0020]     As illustrated in  FIG. 1 , the integrated safety starter  10  may also include a protective plate  18  that serves at least partially to enhance the integration of the components into a quality-controlled assembly. In the illustrated embodiment, the protective plate  18  may be coupled to the contactors  12   a  and  12   b , the safety relay  14 , or both. The protective plate  18  may be designed to block or discourage access to the wires (not shown) interconnecting the contactors  12   a  and  12   b  the safety relay  14 , and the connectors  17   a  and  17   b . In one embodiment, the protective plate  18  may be a face plate that blocks contact with the wires from the front of the integrated safety starter  10 . In alternate embodiments, the protective plate  18  may be mounted elsewhere on the integrated safety starter  10 . Moreover, as illustrated in  FIG. 1 , the protective plate  18  may also include a cut-out region to enable a user to observe lights or other indicators on the safety relay  14 .  
         [0021]     In addition to discouraging access to the interconnecting wires of the integrated safety starter  10 , the protective plate  18  may also protect the contactors  12   a  and  12   b , the safety relay  14 , and the mounting rail  16  from physical damage, during shipment, mounting, or usage. The protective plate  18  may also provide a measure of tamper protection for the integrated safety starter  10 . For example, in one embodiment, a seal or sticker may be placed between the protective plate  18  and the contactors  12   a  and  12   b  or the safety relay  14 , such that removal of the protective plate  18  (i.e., tampering) would be evident by a broken seal. While the provision of such quality control on the integrated unit may be optional, those skilled in the art will readily recognize that such control greatly enhances the reliability of the unit, and reduces the need to field wire the various components. Such control has heretofore been unavailable for safety relays and their related components.  
         [0022]     As described above, the protective plate  18 , in combination with the contactors  12   a  and  12   b , the safety relay  14 , and the mounting rail  16 , provides some measure of tamper protection. For this reason, unlike conventional safety starter systems, the integrated safety starter  10  can be operationally tested and certified, as a complete device by the manufacturer of the integrated safety starter  10  to ensure that contactors  12   a  and  12   b , the safety relay  14 , mounting rail  16 , and the interconnecting wires are functioning properly. Once certified, the manufacturer (or a third party) can designate the integrated safety starter  10  as tested and/or certified using a sticker or seal, as described above. In this way, the manufacturer of the integrated safety starter  10  can produce safety starters with a higher overall quality level. In one embodiment, the manufacturer of the integrated safety starter  10  (or the manufacturer&#39;s representative) may certify that the integrated safety starter  10  meets a “safety integrity level” (“SIL”), such as SIL 3 or SIL 4. Because the integrated safety starter  10  can be manufactured and tested as a single component, the integrated safety starter  10  is more reliable than conventional safety starters that are assembled at the time of use and thus difficult to pre-certify.  
         [0023]     As described above, the integrated safety starter  10  may be configured to facilitate the safe start-up of a motor or other suitable electrical component. Accordingly,  FIG. 2  is a diagrammatical view of a system  30  employing the integrated safety starter  10 , as illustrated in  FIG. 1 , in accordance with one embodiment. For simplicity, like reference numerals have been used to label those elements previously described in regard to  FIG. 1 . As illustrated, the safety relay  14  may be coupled to relay control wires  32 , which may couple a power source and/or controller to the safety relay  14 . The wires  32  may carry a 24 volt dc supply current to the safety relay  14  to enable the safety relay  14  to energize the contactors  12   a  and  12   b . The wires  32  may also be employed to transmit signals between the safety relay  14  and a control system (not shown in  FIG. 2 ). For example, a control system may transmit a signal via the wires  32  that directs the safety relay  14  to energize the contractors  12   a  and  12   b . In one embodiment (not shown), the wires  32  may be coupled to one of the connectors on the mounting rail  16 .  
         [0024]     The safety relay  14  may be coupled to the contactors  12   a  and  12   b  via contactor control wires  36   a  and  36   b . It will be appreciated that a single contactor control wire  36   a  and a single contractor control wire  36   b  are illustrated for illustrative purposes only. As such, in alternate embodiments, more than one contactor control wire  36   a  and  36   b  may run between the safety relay  14  and the contactors  12   a  and  12   b . As described further below, the safety relay  14  may employ the contactor control wires  36   a  and  36   b  to energize the contactors  12   a  and  12   b  or to carry contactor status information between the contactors  12   a  and  12   b  and the safety relay  14  (in a manner similar to conventional auxiliary contacts). For example, the safety relay  14  may employ the wires  36   a  and  36   b  to determine whether the contractors  12   a    12   b  have become fused in either the open position or the closed position.  
         [0025]     As described above, the contactors  12   a  and  12   b  are electrical devices that can be used to control the flow of the power by switching on or off in response to an energizing current. In the embodiment illustrated in  FIG. 2 , the contactors  12   a  and  12   b  are configured to control the flow of power through a load power path  38 . The load power path  38  may comprise one or more wires, contacts, or connectors disposed from a power source (not shown) through the contactors  12   a  and  12   b  to a load (not shown). In one embodiment, the load power path  38  may travel from a 480 voltage source into the connector  17   a , through the contactor  12   b , through the contactor  12   a , and out to a motor through the connector  17   b  on the mounting rail  16 . While the load power path  38  is depicted in  FIG. 2  as a single channel, it will be appreciated that any number of suitable wires may make up the load power path  38 . For example, in a three phase 480 volt system, the load power path  38  may include three wires, one for each phase, as well as conductors for ground and neutral connections.  
         [0026]     Returning now to the safety relay  14 , the safety relay  14  may also be coupled to an emergency stop (“E-Stop”) button  40  via E-Stop signal wires  42   a  and  42   b . As will be described further below, the E-Stop button  40 , also referred to as an emergency off (“EMO”), provides a mechanism for an operator to command the safety relay  14  to open the contactors  12   a  and  12   b  (i.e., to remove power to the load).  
         [0027]     Turning next to the operation of the system  30  in accordance with one embodiment, the integrated safety starter  10  may be employed to verify operating conditions prior to and during the start-up and use of a motor or other piece of industrial equipment. The operation of the integrated system  10  may begin before power is applied to the load current path  38 . As higher voltage levels (e.g., 480 volts) are generally subject to particular control, in accordance with applicable codes, it may be desirable to verify the operability of the contactors  12   a  and  12   b  prior to applying power to the contactors  12   a  and  12   b . For example, during a motor start-up operation, the contactors  12   a  and  12   b  may both initially have an open position or state either by energizing a normally closed contactor or by not energizing a normally open contactor. This open position enables operators of the system  30  to power (i.e., switch on) the motor downstream by closing the contactors  12   a  and  12   b . However, if one or both of the contactors  12   a  and  12   g  is fused in a closed (i.e., conducting) position, turning on the upstream power generator may transmit power to loads through the contactors without their being controlled by their respective control inputs.  
         [0028]     To reduce the chances of developing such unwanted application power to the load, the safety relay  14  within the integrated safety starter  10  may be configured to verify that the contactors  12   a  and  12   b  have not become fused (i.e., are responsive to control inputs). In one embodiment, the contactors  12   a  and  12   b  may be configured such that when the contactor  12   a  or  12   b  is in the open position, a physical switch within the contactor  12   a ,  12   b  closes. As such, the safety relay  14  is able to determine whether one or both of the contactors  12   a ,  12   b  are fused by checking the continuity across that switch. In other words, if the switch is closed when the contactor  12   a ,  12   b  should be open, the contactor  12   a ,  12   b  is most likely fused. It will be appreciated that checking the continuity across a switch is merely one exemplary technique for identifying a malfunction (e.g., a fused contactor). As such, in alternate embodiments, different techniques may be used.  
         [0029]     If the safety relay  14  determines that one or both of the contractors  12   a  and  12   b  are fused, it may indicate or communicate this condition to the operator of the system  30  or to an automatic control device, PLC, or other controller. In one embodiment, the safety relay  14  may also be configured to lock one of the contactors in the open position ( 12   a , for example), if the other contactor ( 12   b , for example), is fused. However, if both of the contactors  12   a  and  12   b  are functioning properly, the safety relay  14  may indicate or communicate this condition to an operator or control device that may subsequently apply power via the load current path  38 . Once power has been applied to the load current path  38 , the safety relay  14  may also facilitate use of that power. Specifically, when directed by an operator or controller, the safety relay  14  may energize or deenergize the contactors  12   a ,  12   b , as appropriate, to close the contactors  12   a  and  12   b  to allow power to flow downstream to the load (e.g., a motor). Similarly, when directed by an operator or controller, the safety relay  14  may energize or deenergize the contactors  12   a  and  12   b , as appropriate, to open the contactors  12   a  and  12   b  to stop the flow of power to the load.  
         [0030]     The safety relay  14  may also energize or deenergize the contactors  12   a  and  12   b  for a variety of other reasons. For example, the safety relay  14  may energize or deenergize the contactors  12   a  and  12   b , as appropriate to open the contactors  12   a  and  12   b  if the safety relay  14  receives an emergency stop signal from the E-Stop  40 . Similarly, the safety relay  14  may energize or deenergize the contactors  12   a  and  12   b  to open the contactors  12   a  and  12   b  if the safety relay  14  identifies certain other conditions. For example, the safety relay  14  may open the contactors  12   a  and  12   b  if the safety relay  14  detects a power surge within the system  30 .  
         [0031]     As described above, the integrated safety starter  10  may be employed to control the flow of electrical power within an electrical system. Many modem systems, however, are moving towards distributed input/output (“I/O”) networked systems. These networked systems employ distributed I/O devices, such as programmable logic devices (“PLD”) or programmable logic controllers (“PLC”), and computer networks, such as Ethernet or DeviceNet (“DNet”) to communicate with and/or control components throughout an electrical system. Accordingly,  FIG. 3  is a diagrammatical view of a system  50  employing a network capable integrated safety starter  52  in accordance with one embodiment. For simplicity, like reference numerals are used to indicate elements previously described in regard to  FIGS. 1 and 2 .  
         [0032]     The network capable integrated safety starter  52  may include the contactors  12   a  and  12   b , the safety relay  14 , the mounting rail  16 , and the protective plate  18 , as described above. In addition, the network capable integrated safety starter  52  may include a network control module  54 . In various embodiments, the network control module  54  may be a PLD, a PLC, a computer or computerized device, or other suitable logic device. The network control module  54  may be configured to receive digital instructions from a controller and to convert these digital signals, when appropriate, into control signals for the safety relay  14 . Similarly, the network control module  54  may receive analog status information from the safety relay  14  and convert this status information, when appropriate, into digital information for the controller. In one embodiment, the network control module  54  may be configured to interface with the GuardLogic™ system commercially available from Rockwell Automation of Milwaukee, Wis.  
         [0033]     As illustrated in  FIG. 3 , the network control module  54  may be coupled to the safety relay  14  via a wire or multi-wire cable  56 . Over this link, the network control module may issue commands to or receive information from the safety relay  14 . For example, the network control module  54  may direct a safety relay  14  to energize or deenergize the contactors  12   a  and  12   b  based on the network control module internal programming or based on commands received from a controller elsewhere in the system  50 . It should be noted that while the network control module and the system relay  14  are depicted in  FIG. 3  as separate components, in alternate embodiments, the network control module  54  and the safety relay  14  may be consolidated into a single component or assembly.  
         [0034]     The network control module may be coupled to a network  60  over a network connection  58 . As will be described further below, the network connection  58  may be any suitable form network connection such as Ethernet cable, fiber optics, and/or wireless transmission (e.g., IEEE 802.11 or WiMax, for example). Similarly, the network  60  may be any form of computer network suitable for interfacing with the network capable integrated safety starter  52 . Examples of suitable networks include but are limited to, local area networks, wide area networks, Intranets, the Ethernet, and so forth.  
         [0035]     Accordingly,  FIG. 4  is a block diagram of a networked motor control system  70  employing the network capable integrated safety starter  52 , as described in  FIG. 3 , in accordance with one embodiment. For simplicity, like reference numbers have been used to designate those features previously described in regard to previous figures. The motor control system  70  includes the network capable integrated safety starter  52 , a power source  72 , and a motor  74 . As described above, the network cable integrated safety starter  52  may be configured to control the flow of power through the load power path  38  from the power generator  72  to the motor  74 . Moreover, as shown, the network capable integrated safety starter  52  may be coupled to the network  60  via the network connection  58 . The network  60  may then be connected to an I/O module  76  which is coupled to a controller  78 . In one embodiment, the I/O module  76  and the controller  78  may be part of a GuardPLC™ 2000 system commercially available from Rockwell Automation of Milwaukee, Wis. In alternate embodiments, different controllers  78  and/or I/O modules  76  may be employed.  
         [0036]     The controller  78  may be coupled to a computer  80  to facilitate operator interaction with the controller  78 . In various embodiments, the computer  80  may be either integrated into the same chassis as the controller  78  or mounted in a separated chassis that is coupled to the controller  78 . As illustrated in  FIG. 4 , the computer  80  may also be coupled to a display, such as a computer monitor, and one or more human input devices  84 , such as a keyboard and/or mouse.  
         [0037]     In operation, an operator of the computer  80  (or a preprogrammed software routine) may control the start-up and operation of a motor or other electrical device using the system  70 . For example, the computer  80  may direct the controller  78  to verify that the network capable integrated safety starter  52  is in the off position (i.e., both contactors in the open state). In response to this command, the controller  78  may communicate via the I/O module  78  and the network  60  to the network control module  54  within the network capable integrated safety starter  52 . The network control module  54  may then confirm with the safety relay  14  that the contactors  12   a  and  12   b  are in their open states. This status information is then communicated back the computer  80  via the network  60 . The computer  80  may then direct the power supply  72  to transmit power to the network capable integrated safety starter  52  via the path  38 . Once power is transmitted to the network capable integrated safety starter  52 , the computer  80  may direct the network capable integrated safety starter  52  (via the network  60  and the safety  78 ) to close the contactors  12   a  and  12   b  so that power can be transmitted to the motor  74 . Once the motor is up and running, the computer  80  may also be configured to command the network capable integrated safety starter  52  to open the contactors  12  and  12   b , as appropriate, to facilitate maintenance or other reasons (e.g., in response to an E-Stop signal).  
         [0038]     While only certain features of the invention have been illustrated and described herein, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.