CONFIGURED TO PROVIDE A FAIL-SAFE MODE

BACKGROUND

1. Field

[0001] Aspects of the present invention generally relate to an electronic circuit breaker configured to provide a fail-safe mode.

2. Description of the Related Art

[0002] Electronic components have become more common in circuit breakers, such as arc fault circuit interrupters (AFCIs), ground fault circuit interrupters (GFCIs), and recently solid-state circuit breakers. Although providing many advantages over traditional thermal magnetic circuit breakers, such as advance fault detection and short interruption times, electronic circuit breakers, especially the control circuits, are subject to damage from overvoltage events.

[0003] Overvoltage events are not evitable in circuit breaker applications as they can be generated in natural situations like lightning strikes. To protect electronic circuit breakers from overvoltage events, overvoltage protection components are used. The most common component is a Metal-Oxide Varistor (MOV). A MOV has the advantage of low cost and high energy absorption. However, MO Vs degrade after repetitive usage and will lose their protection capabilities. It is necessary to ensure the circuit breakers stay in a safe mode, for example, at trip or off position, when MO Vs lose their protection. A method needs to be provided to open circuit breakers when overvoltage components lose protection capabilities. [0004] There are two ways to provide better protection up to date. First, the overvoltage components are normally oversized for the application to increase lifespan of the components. Second, when overvoltage components fail, leakage current causes heat in the components. The heat can be used to trigger certain mechanism to open circuit. However, both ways are inadequate.

[0005] Therefore, there is a need for a better overvoltage protection mechanism for an electronic circuit breaker.

SUMMARY

[0006] Briefly described, aspects of the present invention relate to an electronic circuit breaker configured to provide a fail-safe mode. A fail-safe mode in an electronic circuit breaker is defined as: if there is malfunction or if the electronic circuit breaker loses designed capabilities of protection, the electronic circuit breaker should cut off power to avoid hazards, such as fire and personal injuries. It is common among AFCIs, GFCIs devices and solid-state circuit breakers that an overvoltage protection component is used. Although there are many overvoltage protection methods, the most common one is clamping devices, such as Metal-Oxide Varistors (MOVs), a Transient Voltage Suppressor (TVS) and so on. Under overvoltage conditions, clamping devices can hold the voltage at the threshold voltage and absorb the excessive energies. MOVs are more often used for their lower cost and higher energy absorption. It is common that when clamping devices start to fail, leakage current occurs at lower voltages and eventually leads to the failure of the components. This invention is aimed to detect the leakage current of these components and hence leaves the circuit breakers in safe mode before component failure. The method monitors leakage current of clamping components. It has better accuracy and faster reaction time compared to the thermal approach. Also, for GFCIs, the primary differential current transformer (CT) can be used, no extra components are needed.

[0007] In accordance with one illustrative embodiment of the present invention, an electronic circuit breaker is configured to provide a fail-safe mode. It comprises an overvoltage protection device, a sensing and control circuit configured to open an air gap and a differential current transformer disposed directly on a current path of the overvoltage protection device to monitor a leakage current and detect the leakage current of the overvoltage protection device and hence leave the circuit breaker in a safe mode before component failure. The differential current transformer to see a net current of IM, and trigger the sensing and control circuit to open the air gap.

[0008] In accordance with one illustrative embodiment of the present invention, a method of providing a fail-safe mode in an electronic circuit breaker. The method comprises providing an overvoltage protection device, providing a sensing and control circuit configured to open an air gap and providing a differential current transformer disposed directly on a current path of the overvoltage protection device to monitor a leakage current and detect the leakage current of the overvoltage protection device and hence leave the circuit breaker in a safe mode before component failure. The differential current transformer to see a net current of IM, and trigger the sensing and control circuit to open the air gap.

[0009] The above described features and advantages, as well as others, will become more readily apparent to those of ordinary skill in the art by reference to the following detailed description and accompanying drawings. While it would be desirable to provide one or more of these or other advantageous features, the teachings disclosed herein extend to those embodiments which fall within the scope of the appended claims, regardless of whether they accomplish one or more of the above-mentioned advantages. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] For a more complete understanding of the present disclosure, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, wherein like numbers designate like objects.

[0011] FIG. 1 illustrates an AFCI construction in accordance with an exemplary embodiment of the present invention.

[0012] FIG. 2 illustrates a GF CI construction in accordance with an exemplary embodiment of the present invention.

[0013] FIG. 3 illustrates a solid-state circuit breaker construction in accordance with an exemplary embodiment of the present invention.

[0014] FIG. 4 illustrates a proposed GFCI construction with a rearranged overvoltage component connection - overvoltage component in good condition in accordance with an exemplary embodiment of the present invention.

[0015] FIG. 5 illustrates a Proposed GFCI construction with a rearranged overvoltage component connection - overvoltage component starts to fail in accordance with an exemplary embodiment of the present invention.

[0016] FIG. 6 illustrates a proposed AFCI construction in accordance with an exemplary embodiment of the present invention.

[0017] FIG. 7 illustrates a proposed solid-state circuit breaker construction in accordance with an exemplary embodiment of the present invention.

[0018] FIG. 8 illustrates a schematic view of a flow chart of a method of providing a fail-safe mode in an electronic circuit breaker in accordance with an exemplary embodiment of the present invention.

DETAILED DESCRIPTION

[0019] Various technologies that pertain to systems and methods that facilitate overvoltage protection mechanism for an electronic circuit breaker will now be described with reference to the drawings, where like reference numerals represent like elements throughout. The drawings discussed below, and the various embodiments used to describe the principles of the present disclosure in this patent document are by way of illustration only and should not be construed in any way to limit the scope of the disclosure. Those skilled in the art will understand that the principles of the present disclosure may be implemented in any suitably arranged apparatus. It is to be understood that functionality that is described as being carried out by certain system elements may be performed by multiple elements. Similarly, for instance, an element may be configured to perform functionality that is described as being carried out by multiple elements. The numerous innovative teachings of the present application will be described with reference to exemplary non-limiting embodiments.

[0020] To facilitate an understanding of embodiments, principles, and features of the present invention, they are explained hereinafter with reference to implementation in illustrative embodiments. In particular, they are described in the context of an electronic circuit breaker configured to provide a fail-safe mode. Embodiments of the present invention, however, are not limited to use in the described devices or methods. [0021] The components and materials described hereinafter as making up the various embodiments are intended to be illustrative and not restrictive. Many suitable components and materials that would perform the same or a similar function as the materials described herein are intended to be embraced within the scope of embodiments of the present invention.

[0022] These and other embodiments of the overvoltage protection mechanism for an electronic circuit breaker according to the present disclosure are described below with reference to FIGs. 1-8 herein. Like reference numerals used in the drawings identify similar or identical elements throughout the several views. The drawings are not necessarily drawn to scale.

[0023] Consistent with one embodiment of the present invention, FIG. 1 represents an AFCI construction 100 in accordance with an exemplary embodiment of the present invention. An arc-fault circuit interrupter (AFCI) is configured to detect a wide range of arcing electrical faults to help reduce an electrical system from being an ignition source of a fire.

[0024] Referring to FIG. 2, it illustrates a GFCI construction 200 in accordance with an exemplary embodiment of the present invention. A ground-fault circuit interrupter (GFCI) is configured to shut off electric power in an event of a ground-fault.

[0025] Turning now to FIG. 3, it illustrates a solid-state circuit breaker construction 300 in accordance with an exemplary embodiment of the present invention. A solid-state circuit breaker (SSCB) replaces traditional moving parts of an electromechanical circuit breaker with semiconductors and advanced software algorithms that control power and can interrupt extreme currents faster.

[0026] FIGs. 1-3 show common structures of AFCIs, GFCIs and solid-state circuit breakers. It is common among these devices that an overvoltage protection component is used. Although there are many overvoltage protection methods, the most common one is clamping devices, such as MO Vs, TVS and so on. Under overvoltage conditions, clamping devices can hold the voltage at the threshold voltage and absorb the excessive energies. MOVs are more often used for their lower cost and higher energy absorption. It is common that when clamping devices start to fail, leakage current occurs at lower voltages and eventually leads to the failure of the components. This invention is aimed to detect the leakage current of these components and hence leaves the circuit breakers in safe mode before component failure.

[0027] FIG. 4 illustrates a proposed GFCI 400 with a rearranged overvoltage component connection - overvoltage component in good condition in accordance with an exemplary embodiment of the present invention. For GFCIs or other circuit breakers that already have differential current transformers, FIGs. 4-5 show the proposed structure. A same differential current transformer (CT) 405 used for ground fault detection can also be used for overvoltage component leakage current detection, with no extra components added. To achieve detection of leakage current, one side of a clamping device 407 is tapped on a line side 410(1) of the CT 405 and the other side is tapped on a load side 410(2) of the CT 405. When the clamping device 407 is in good condition, no leakage current occurs, so a total current, IT, is equal to a load current, II. With a complete current loop, the CT 405 sees net zero current and will not trigger a sensing and control circuit 415 to open an air gap 417, as shown in FIG. 4. When the clamping device 407 is compromised, a leakage current, IM, is present. As shown in FIG. 5, the CT 405 now sees net current of IM, and can trigger the sensing and control circuit 415 to open the air gap 417 and leave the breaker 400 in a trip position. This method is convenient for GFCIs, since differential CTs are already present, and only rearrangement of wiring is needed. However, other types of electronic circuit breakers can also use the method by adding a differential CT or a current transformer directly on the clamping device current path to monitor leakage current.

[0028] An electronic circuit breaker such as the GFCI 400 is configured to provide a fail-safe mode. The GFCI 400 comprises an overvoltage protection device such as the clamping device 407. The overvoltage protection device may be a Metal-Oxide Varistor (MOV) or a Transient Voltage Suppressor (TVS).

[0029] The GFCI 400 further comprises the sensing and control circuit 415 configured to open the air gap 417. The GFCI 400 further comprises the differential current transformer (CT) 405 disposed directly on a current path of the overvoltage protection device 407 to monitor a leakage current and detect the leakage current of the overvoltage protection device 407 and hence leave the GFCI 400 in a safe mode before component failure. The differential current transformer 405 to see a net current of IM, and trigger the sensing and control circuit 415 to open the air gap 417 and leave the GFCI 400 in a trip position.

[0030] The differential current transformer 405 is the same differential current transformer that is being used for ground fault detection and it can also be used for overvoltage component leakage current detection, with no extra components added. To achieve detection of the leakage current, one side of the overvoltage protection device 407 is tapped on a line side of the differential current transformer 405 and other side of the overvoltage protection device 407 is tapped on a load side of the differential current transformer 405. When the overvoltage protection device 407 is in a good condition, no leakage current occurs, so a total current, IT, is equal to a load current, IL such that with a complete current loop, the differential current transformer 405 sees a net zero current and will not trigger the sensing and control circuit 415 to open the air gap 417.

[0031] As seen in FIG. 5, it illustrates the GFCI 400 with a rearranged overvoltage component connection - overvoltage component starts to fail in accordance with an exemplary embodiment of the present invention. When the overvoltage protection device 407 is compromised, the net current of IM as a leakage current, IM, is present such that the differential current transformer now sees the net current of IM, and triggers the sensing and control circuit 415 to open the air gap 417 and leave the GFCI 400 in a trip position. When the overvoltage protection device 407 starts to fail, the leakage current occurs at lower voltages and eventually leads to failure of components.

[0032] As shown in FIG. 6, it illustrates a AFCI 600 in accordance with an exemplary embodiment of the present invention. FIGs. 1-3 show that the basic structures of all three circuit breakers (AFCI, GFCI, Solid-State) are similar. For the AFCI 600, an arc fault detection sensor 605 is used to gather high frequency current information for arc fault detection. To realize what is described in FIG. 4, a current transformer 610 as shown in FIG. 4 can be added and connected in the same fashion. The arc fault detection sensor 605 can be a current sensor, from which a high frequency signal is extracted to make a decision on arcing.

[0033] In FIG. 7, it illustrates a solid-state circuit breaker 700 in accordance with an exemplary embodiment of the present invention. For the solid-state circuit breaker 700, a set of solid-state switching components 705 are added to the current path and can interrupt the current independent of an air gap 707. To realize what is described in FIG. 4, a current transformer 710 is also added as in FIG. 4.

[0034] With regard to FIG. 8, it illustrates a schematic view of a flow chart of a method 800 of providing a fail-safe mode in an electronic circuit breaker in accordance with an exemplary embodiment of the present invention. Reference is made to the elements and features described in FIGs. 1-7. It should be appreciated that some steps are not required to be performed in any particular order, and that some steps are optional.

[0035] The method 800 comprises a step 805 of providing an overvoltage protection device. The method 800 further comprises a step 810 of providing a sensing and control circuit configured to open an air gap. The method 800 further comprises a step 815 of providing a differential current transformer disposed directly on a current path of the overvoltage protection device to monitor a leakage current and detect the leakage current of the overvoltage protection device and hence leave the circuit breaker in a safe mode before component failure. The differential current transformer to see a net current of IM, and trigger the sensing and control circuit to open the air gap and leave the circuit breaker in a trip position.

[0036] While a design of three circuit breakers (AFCI, GFCI, Solid-State) is described here a range of one or more other circuit breakers are also contemplated by the present invention. For example, other circuit breakers may be implemented based on one or more features presented above without deviating from the spirit of the present invention.

[0037] The techniques described herein can be particularly useful for an overvoltage protection device such as a clamping device. While particular embodiments are described in terms of the clamping device, the techniques described herein are not limited to such devices but can also be used with other overvoltage protection devices.

[0038] While embodiments of the present invention have been disclosed in exemplary forms, it will be apparent to those skilled in the art that many modifications, additions, and deletions can be made therein without departing from the spirit and scope of the invention and its equivalents, as set forth in the following claims.

[0039] Embodiments and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments that are illustrated in the accompanying drawings and detailed in the following description. Descriptions of well-known starting materials, processing techniques, components and equipment are omitted so as not to unnecessarily obscure embodiments in detail. It should be understood, however, that the detailed description and the specific examples, while indicating preferred embodiments, are given by way of illustration only and not by way of limitation. Various substitutions, modifications, additions and/or rearrangements within the spirit and/or scope of the underlying inventive concept will become apparent to those skilled in the art from this disclosure.

[0040] As used herein, the terms “comprises,” “comprising,” “includes,” “including,” “has,” “having” or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a process, article, or apparatus that comprises a list of elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such process, article, or apparatus.

[0041] Additionally, any examples or illustrations given herein are not to be regarded in any way as restrictions on, limits to, or express definitions of, any term or terms with which they are utilized. Instead, these examples or illustrations are to be regarded as being described with respect to one particular embodiment and as illustrative only. Those of ordinary skill in the art will appreciate that any term or terms with which these examples or illustrations are utilized will encompass other embodiments which may or may not be given therewith or elsewhere in the specification and all such embodiments are intended to be included within the scope of that term or terms.

[0042] In the foregoing specification, the invention has been described with reference to specific embodiments. However, one of ordinary skill in the art appreciates that various modifications and changes can be made without departing from the scope of the invention. Accordingly, the specification and figures are to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope of invention.

[0043] Although the invention has been described with respect to specific embodiments thereof, these embodiments are merely illustrative, and not restrictive of the invention. The description herein of illustrated embodiments of the invention is not intended to be exhaustive or to limit the invention to the precise forms disclosed herein (and in particular, the inclusion of any particular embodiment, feature or function is not intended to limit the scope of the invention to such embodiment, feature or function). Rather, the description is intended to describe illustrative embodiments, features and functions in order to provide a person of ordinary skill in the art context to understand the invention without limiting the invention to any particularly described embodiment, feature or function. While specific embodiments of, and examples for, the invention are described herein for illustrative purposes only, various equivalent modifications are possible within the spirit and scope of the invention, as those skilled in the relevant art will recognize and appreciate. As indicated, these modifications may be made to the invention in light of the foregoing description of illustrated embodiments of the invention and are to be included within the spirit and scope of the invention. Thus, while the invention has been described herein with reference to particular embodiments thereof, a latitude of modification, various changes and substitutions are intended in the foregoing disclosures, and it will be appreciated that in some instances some features of embodiments of the invention will be employed without a corresponding use of other features without departing from the scope and spirit of the invention as set forth. Therefore, many modifications may be made to adapt a particular situation or material to the essential scope and spirit of the invention.

[0044] Respective appearances of the phrases "in one embodiment," "in an embodiment," or "in a specific embodiment" or similar terminology in various places throughout this specification are not necessarily referring to the same embodiment. Furthermore, the particular features, structures, or characteristics of any particular embodiment may be combined in any suitable manner with one or more other embodiments. It is to be understood that other variations and modifications of the embodiments described and illustrated herein are possible in light of the teachings herein and are to be considered as part of the spirit and scope of the invention.

[0045] In the description herein, numerous specific details are provided, such as examples of components and/or methods, to provide a thorough understanding of embodiments of the invention. One skilled in the relevant art will recognize, however, that an embodiment may be able to be practiced without one or more of the specific details, or with other apparatus, systems, assemblies, methods, components, materials, parts, and/or the like. In other instances, well-known structures, components, systems, materials, or operations are not specifically shown or described in detail to avoid obscuring aspects of embodiments of the invention. While the invention may be illustrated by using a particular embodiment, this is not and does not limit the invention to any particular embodiment and a person of ordinary skill in the art will recognize that additional embodiments are readily understandable and are a part of this invention.

[0046] It will also be appreciated that one or more of the elements depicted in the drawings/figures can also be implemented in a more separated or integrated manner, or even removed or rendered as inoperable in certain cases, as is useful in accordance with a particular application.

[0047] Benefits, other advantages, and solutions to problems have been described above with regard to specific embodiments. However, the benefits, advantages, solutions to problems, and any component(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, or essential feature or component.