Patent Application
20240426913
This application is related to co-pending U.S. Application, entitled “DETECTING WELDED RELAY CONTACTS USING ELECTRICAL PULSE,” (Docket No. 2023P-089-US), filed concurrently, which is hereby incorporated by reference in its entirety for all purposes.
This application is related to co-pending U.S. Application, entitled “DETECTING WELDED RELAY CONTACTS USING CONTACT CLOSE TIME MEASUREMENT,” (Docket No. 2023P-091-US), filed concurrently, which is hereby incorporated by reference in its entirety for all purposes.
This application is related to co-pending U.S. Application, entitled “DETECTING WELDED RELAY CONTACTS USING SPANNER VOLTAGE MEASUREMENT,” (Docket No. 2023P-092-US), filed concurrently, which is hereby incorporated by reference in its entirety for all purposes.
In modern industrial environments relay systems are commonly used to control the supply of power to industrial equipment such as motors and the like. These relay systems commonly include a plurality of individual relays. For example, a relay system to control three-phase electrical power supplied to a piece of equipment typically includes one or more relay for each phase of the electrical power.
Over repeated operation of relay systems, materials within the contacts of the individual relays may segregate, resulting in increased concentrations of particular metal elements within small regions of the contacts. Eventually this segregation may result in metal migration such that a relay contact is welded shut.
In double break contact relays, where each relay includes two contacts, it is straightforward to determine when both contacts of the relay are shorted. However, in situations where only one of the contacts within the relay is welded detection of the weld is much more difficult.
In an implementation, a system includes a relay system and a controller. The relay system includes a relay having a first contact on an input side of the relay, the input side coupled to a power source, and a second contact on a load side of the relay is coupled to a load.
The controller includes one or more processors and a memory having stored thereon instructions that, upon execution by the one or more processors, cause the one or more processors to perform a weld detection check.
The weld detection check includes monitoring a current flow from the power source through the relay, transmitting a close signal to the relay, and transmitting an open signal to the relay.
Based on the current flow through the relay following the open signal, the controller determines whether an electrical weld of one of the first contact and the second contact of the relay exists.
In another implementation, a method for detecting a welded relay contact by performing a weld detection check, includes closing a relay, wherein the relay comprises a first contact on an input side of the relay and a second contact on a load side of the relay, and wherein the input side of the relay is coupled to a power source, and the load side of the relay is coupled to a load.
The method also includes opening the relay, and measuring a current flow through the relay in response to opening the relay. Based on the current flow through the relay, the method determines whether an electrical weld of one of the first contact and the second contact of the relay exists.
Many aspects of the disclosure may be better understood with reference to the following drawings. While several implementations are described in connection with these drawings, the disclosure is not limited to the implementations disclosed herein. On the contrary, the intent is to cover all alternatives, modifications, and equivalents.
The following descriptions of various example embodiments and implementations of a system and method for the detection of welded relay contacts using electrical pulses. As discussed above, relay systems are commonly used in the control of industrial machines. In some example embodiments, relay systems are used within motor starter controllers. These devices are used to start industrial electrical motors powered by a multi-phase power source. Typically, these power sources have three phases of alternating current (AC) power with each phase offset from the others by 120° and require relay systems having three or more relays.
When a relay is shorted within such a controller, a reversing device will suffer a line-to-line short circuit of two phases of the power source internally if a relay on the reversing phases welds. This results in a catastrophic failure and the controller may be damaged or destroyed by the event. While this example embodiment, describes a motor starter controller, many other similar controllers and their associated industrial machines suffer similar failures if a weld is undetected and the relay shorts.
In this example embodiment, single welded double break relay contacts are detected by monitoring the current flowing through the relay during open and close operations of the relay. Initially, the relay is closed and current flows normally through the relay. Then and open signal is transmitted to the relay and the relay opens. If the relay is partially welded its response to the open signal is different from that of a non-welded relay and this different response is detectable by monitoring the current flow through the relay.
After the open signal is applied to the relay and the relay opens, if current continues to flow through the relay, this indicates that a weld exists on at least one of the contacts of the relay.
Other example embodiments measure the voltage across the relay (between the contacts of the relay) to detect welds. After the open signal is transmitted to the relay, a relay with a weld will attempt to open, but bounce back closed one or more times. This failure is detected by monitoring the voltage across the relay and detecting if the voltage returns to zero after the open signal is transmitted to the relay.
This solution for detecting single welded relays provides a technical advantage by detecting these failures before they cause short circuits within the controller. This early detection allows a user to replace the controller before a potentially destructive failure of the controller.
In this example, all of the relays: R1F 121, R1R 122, R2F 123, R2R 124, and R3125 are off. However, relay R2R 124 has a first contact 130 which is welded shut.
A second relay (R2R 124) is also illustrated with a first contact 130 on an input side (L2102) of the second relay, and a second contact 210 on a load side (T2112) of the second relay. In this example, the first contact 130 of the second relay R2R 124 is welded.
Since the first contact 130 of the second relay R2R 124 is welded, the second contact 210 of the second relay R2R 124 has a much smaller than normal gap, and when voltage is applied, an arc may form across that gap and short the second relay R2R 124. This causes a short circuit between two phases of the input power source L1101 and L2102 as current flows through path 220. This short circuit may result in substantial damage to the power source and other equipment connected to relay system 200.
In this example, relay system 310 includes current sensor 316. This current sensor 316 utilizes any of a wide variety of configurations and implementations while serving to detect welds. Here, relay system 310 includes input 322 coupled to power source 340 which includes a connection to ground 330. The load side 324 of relay 312 within relay system 310 is connected to LOAD 342 representing a load within an industrial machine within industrial automation environment 300, such as an electrical motor. Voltage sensor 350 is coupled to relay 312 at nodes 326 and 328 is a configuration to measure a voltage across relay 312. This voltage sensor 350 utilizes any of a wide variety of configurations and implementations while serving to detect welds. In this example, a first contact 314 of relay 312 is welded shut.
In relays having a weld (such as relay 312) the relay is slower to open than non-welded relays resulting in current flowing through the relay after it should have opened. This is detected by current sensor 316. Also, relays having a single weld may bounce open and closed one or more times after receiving open signal 610. This bouncing is illustrated by dashed line 620. Voltage sensor 350 detects these bounces by measuring the voltage across relay 312 and detecting when the voltage across the relay returns to zero one or more times after the relay opens.
In some example embodiments, relay system 310 includes a plurality of relays and the steps illustrated in
In some example embodiments, the steps illustrated in
In response to detecting a weld, some example embodiments perform a system shutdown or disconnect the power source to prevent damage to the system and broadcast an alert message notifying users of the weld and the shutdown.
Initially relay 312 is closed and the voltage 720 across the relay is zero while the current 710 through relay 312 tracks the current supplied by power source 340. At time t1 731 an open signal is transmitted to relay 312. At time t2 732 relay 312 attempts to open. However, since one side of relay 312 is welded, only one side of the relay opens.
At time t3 733, the current 710 through relay 312 should be zero, however here the current 710 keeps flowing through relay 312 indicating the presence of a weld. At time t4 734, the non-welded contact of relay 312 rebounds and closed again and the voltage 720 across relay 312 is once again zero.
Between times t4 734 and t5 735 several bounces are illustrated by the voltage 720 across relay 312 decreasing below a threshold voltage, while current 710 continues to flow through relay 312, indicating a welded contact. The threshold voltage is less than the normal voltage across relay 312 when relay 312 is open and greater than zero. In some implementations, the voltage 720 across relay 312 is negative, and an absolute value of the voltage is compared to the threshold voltage.
In this example embodiment, controller 820 includes processing circuitry 830, internal storage system 840, input port 822, and output port 824. Processing circuitry 830 is coupled with internal storage system 840 through link 801. Processing circuitry 830 is also coupled with relay system 850 through link 802.
Input port 822 is configured to receive control signals and data from external computing devices (not illustrated). Output port 824 is configured to provide control signals and data to external computing devices (not illustrated).
Processing circuitry 830 comprises electronic circuitry configured to direct control system 810 to control machine 860, and to detect a welded relay contact within relay system 850 by performing a weld detection check as described above. Processing circuitry 830 may comprise microprocessors and other circuitry that retrieves and executes software 842. Examples of processing circuitry 830 include general purpose central processing units, application specific processors, and logic devices, as well as any other type of processing device, combinations, or variations thereof. Processing circuitry 830 may be implemented within a single processing device but may also be distributed across multiple processing devices or sub-systems that cooperate in executing program instructions.
Internal storage system 840 may comprise any non-transitory computer readable storage media capable of storing software 842 that is executable by processing circuitry 830. Internal storage system 840 may also include various data structures 844 which comprise one or more registers, databases, tables, lists, or other data structures. Storage system 840 may include volatile and nonvolatile, removable and non-removable media implemented in any method or technology for storage of information, such as computer readable instructions, data structures, program circuits, or other data.
Storage system 840 may be implemented as a single storage device but may also be implemented across multiple storage devices or sub-systems co-located or distributed relative to each other. Storage system 840 may comprise additional elements, such as a controller, capable of communicating with processing circuitry 830. Examples of storage media include random access memory, read only memory, magnetic disks, optical disks, flash memory, virtual memory and non-virtual memory, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium which may be used to store the desired information and that may be accessed by an instruction execution system, as well as any combination or variation thereof.
Software 842 may be implemented in program instructions and among other functions may, when executed by controller 820 in general, or processing circuitry 830 in particular, direct controller 820, or processing circuitry 830, to operate as described herein to control machine 860, and to detect a welded relay contact within relay system 850 by performing a weld detection check. Software 842 may include additional processes, programs, or components, such as operating system software, database software, or application software. Software 842 may also comprise firmware or some other form of machine-readable processing instructions executable by elements of processing circuitry 830.
In general, software 842 may, when loaded into processing circuitry 830 and executed, transform processing circuitry 840 overall from a general-purpose computing system into a special-purpose computing system customized to operate as described herein for a controller 820 configured to control machine 860, and to detect a welded relay contact within relay system 850 by performing a weld detection check, among other operations. Encoding software 842 on internal storage system 840 may transform the physical structure of internal storage system 840. The specific transformation of the physical structure may depend on various factors in different implementations of this description. Examples of such factors may include, but are not limited to the technology used to implement the storage media of internal storage system 840 and whether the computer-storage media are characterized as primary or secondary storage.
For example, if the computer-storage media are implemented as semiconductor-based memory, software 842 may transform the physical state of the semiconductor memory when the program is encoded therein. For example, software 842 may transform the state of transistors, capacitors, or other discrete circuit elements constituting the semiconductor memory. A similar transformation may occur with respect to magnetic or optical media. Other transformations of physical media are possible without departing from the scope of the present description, with the foregoing examples provided only to facilitate this discussion.
Controller 820 transmits an open signal 610 to relay 312, (operation 902). Current sensor 316 measures a current flow through relay 312 after opening the relay 312, (operation 904); and based on the current flow through the relay 312, controller 820 determines whether an electrical weld 314 of one of the first contact and the second contact of the relay 312 exists, (operation 906).
The included descriptions and figures depict specific embodiments to teach those skilled in the art how to make and use the best mode. For the purpose of teaching inventive principles, some conventional aspects have been simplified or omitted. Those skilled in the art will appreciate variations from these embodiments that fall within the scope of the invention. Those skilled in the art will also appreciate that the features described above may be combined in various ways to form multiple embodiments. As a result, the invention is not limited to the specific embodiments described above, but only by the claims and their equivalents.
A device that is “configured to” perform a task or function may be configured (e.g., programmed and/or hardwired) at a time of manufacturing by a manufacturer to perform the function and/or may be configurable (or reconfigurable) by a user after manufacturing to perform the function and/or other additional or alternative functions. The configuring may be through firmware and/or software programming of the device, through a construction and/or layout of hardware components and interconnections of the device, or a combination thereof.
A circuit or device that is described herein as including certain components may instead be coupled to those components to form the described circuitry or device. For example, a structure described as including one or more semiconductor elements (such as transistors), one or more passive elements (such as resistors, capacitors, and/or inductors), and/or one or more sources (such as voltage and/or current sources) may instead include only the semiconductor elements within a single physical device (e.g., a semiconductor die and/or integrated circuit (IC) package) and may be coupled to at least some of the passive elements and/or the sources to form the described structure either at a time of manufacture or after a time of manufacture, for example, by an end-user and/or a third-party.
While certain components may be described herein as being of a particular process technology, these components may be exchanged for components of other process technologies. Circuits described herein are reconfigurable to include the replaced components to provide functionality at least partially similar to functionality available prior to the component replacement. Components shown as relays, unless otherwise stated, are generally representative of any one or more elements configured to operate as a relay or switch. Such relay components include relays, contactors, and similar components.
Components shown as resistors, unless otherwise stated, are generally representative of any one or more elements coupled in series and/or parallel to provide an amount of impedance represented by the shown resistor. For example, a resistor or capacitor shown and described herein as a single component may instead be multiple resistors or capacitors, respectively, coupled in parallel between the same terminals. For example, a resistor or capacitor shown and described herein as a single component may instead be multiple resistors or capacitors, respectively, coupled in series between the same two terminals as the single resistor or capacitor.
Uses of the phrase “ground voltage potential” in the foregoing description include a chassis ground, an Earth ground, a floating ground, a virtual ground, a digital ground, a common ground, and/or any other form of ground connection applicable to, or suitable for, the teachings of this description. In this description, unless otherwise stated, “about,” “approximately” or “substantially” preceding a parameter means being within +/−10 percent of that parameter. Modifications are possible in the described examples, and other examples are possible within the scope of the claims.
