Patent Application
20070076333
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.
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.
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.
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.
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.
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.
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.
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.
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.
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:
Turning now to the drawings, and referring first to
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 12a is a normally open contactor and the contactor 12b is a normally closed contactor.
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 12a and 12b 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
As illustrated in
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 17a and 17b that may be coupled to wires or traces that interconnect the connectors 17a and 17b to the contactors 12a and 12b and/or the safety relay 14. In one embodiment, the connector 17a is configured to be coupled to a power supply (i.e., the upstream side of an electrical enclosure) and the connector 17b is configured to be coupled to the load side (i.e., the downstream side of an electrical enclosure) with wires interconnecting the connectors 17a and 17b, the contactors 12a and 12b, and safety relay 14, as will be described in greater detail in regard to
As illustrated in
In addition to discouraging access to the interconnecting wires of the integrated safety starter 10, the protective plate 18 may also protect the contactors 12a and 12b, 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 12a and 12b 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.
As described above, the protective plate 18, in combination with the contactors 12a and 12b, 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 12a and 12b, 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'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.
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,
The safety relay 14 may be coupled to the contactors 12a and 12b via contactor control wires 36a and 36b. It will be appreciated that a single contactor control wire 36a and a single contractor control wire 36b are illustrated for illustrative purposes only. As such, in alternate embodiments, more than one contactor control wire 36a and 36b may run between the safety relay 14 and the contactors 12a and 12b. As described further below, the safety relay 14 may employ the contactor control wires 36a and 36b to energize the contactors 12a and 12b or to carry contactor status information between the contactors 12a and 12b and the safety relay 14 (in a manner similar to conventional auxiliary contacts). For example, the safety relay 14 may employ the wires 36a and 36b to determine whether the contractors 12a 12b have become fused in either the open position or the closed position.
As described above, the contactors 12a and 12b 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
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 42a and 42b. 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 12a and 12b (i.e., to remove power to the load).
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 12a and 12b prior to applying power to the contactors 12a and 12b. For example, during a motor start-up operation, the contactors 12a and 12b 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 12a and 12b. However, if one or both of the contactors 12a and 12g 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.
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 12a and 12b have not become fused (i.e., are responsive to control inputs). In one embodiment, the contactors 12a and 12b may be configured such that when the contactor 12a or 12b is in the open position, a physical switch within the contactor 12a, 12b closes. As such, the safety relay 14 is able to determine whether one or both of the contactors 12a, 12b are fused by checking the continuity across that switch. In other words, if the switch is closed when the contactor 12a, 12b should be open, the contactor 12a, 12b 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.
If the safety relay 14 determines that one or both of the contractors 12a and 12b 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 (12a, for example), if the other contactor (12b, for example), is fused. However, if both of the contactors 12a and 12b 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 12a, 12b, as appropriate, to close the contactors 12a and 12b 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 12a and 12b, as appropriate, to open the contactors 12a and 12b to stop the flow of power to the load.
The safety relay 14 may also energize or deenergize the contactors 12a and 12b for a variety of other reasons. For example, the safety relay 14 may energize or deenergize the contactors 12a and 12b, as appropriate to open the contactors 12a and 12b 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 12a and 12b to open the contactors 12a and 12b if the safety relay 14 identifies certain other conditions. For example, the safety relay 14 may open the contactors 12a and 12b if the safety relay 14 detects a power surge within the system 30.
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,
The network capable integrated safety starter 52 may include the contactors 12a and 12b, 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.
As illustrated in
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.
Accordingly,
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
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 12a and 12b 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 12a and 12b 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 12b, as appropriate, to facilitate maintenance or other reasons (e.g., in response to an E-Stop signal).
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.
