Patent Application
20210249199
Aspects of the present invention generally relate to silver-graphene tungsten material electrical contact tips of a low voltage circuit breaker.
Conventional electrical contact materials are silver based refractory composite. They are widely applied in low voltage circuit breakers and switches and must withstand arc erosion, contact interface resistance, and resist welding. The challenges of the electrical contact materials are focused on various formulas and their percentages in weight to optimize and balance their properties to meet multiple applications. The typical compositions of Ag base refractory contacts are most commonly paired with W, WC, Mo, C powder metal and with CdO, SnO2, NiO, ZnO metal oxide particles.
Silver tungsten composite material is widely applied in low voltage circuit breakers. AgW50 is a typical composite material, comprised of 50% silver and 50% tungsten in weight. Despite its wide use in low voltage molded case circuit breakers, it still has its challenges when it comes to breaker performance in regard to arcing erosion, welding, and contact resistance.
Therefore, there is a need for electrical contact materials that improve conventional electrical contact material performance in arcing erosion and arcing energy.
Briefly described, aspects of the present invention relate to silver-graphene tungsten material electrical contact tips of a low voltage circuit breaker. Two different percentage of graphene materials as additively mixed in AgW50 electrical contact material to form (AgGr0.3)W50 and (AgGr0.5)W50 to improve conventional electrical contact material performance in arcing erosion and arcing energy. (AgGr)W50 exhibited a total mass loss of 3.8% which is the lowest of all tested. Functional testing has shown that arcing energy was reduced by 27.1% and 7.4% when testing at 5 kA and 65 kA respectively as compared to AgW50 material. Metallurgical analysis shows that a unique 2-D graphene structure has been observed from the fractography SEM images of silver-graphene tungsten contacts, which is inherited by (AgGr) composite material. Furthermore (AgGr)W50 microstructure images present great uniform mixing while tungsten distributes in the silver-graphene matrix in comparison with traditional silver tungsten material. Utilizing a PM process, silver-graphene-tungsten (AgGr0.3)W50 and (AgGr0.5)W50 contact tips were successfully produced. The PM process (press, sinter, and re-press) is the same process that is used to make AgW50 contact tips.
In accordance with one illustrative embodiment of the present invention, a contact tip of a circuit breaker is provided. The contact tip comprises an electrical contact material comprising silver-graphene (AgGr) with a graphene material (Gr) in a range of 0.1% to 1.0% additively mixed in Ag as being denoted as AgGr0.3% (Ag 99.7% and Gr0.3% in weight) which is mixed with tungsten (W) to form (AgGr0.3)W50 ((AgGr0.3)50% and W50% in weight) called a silver-graphene tungsten composite material.
In accordance with one illustrative embodiment of the present invention, a contact tip of a circuit breaker is provided. The contact tip comprises an electrical contact material comprising silver (Ag) and tungsten (W) and a graphene material (Gr) in a range of 0.1% to 1.0% additively mixed in Ag as being denoted as AgGr0.5% (Ag 99.5% and Gr 0.5% in weight) which is mixed with tungsten (W) to form (AgGr0.5)W50 ((AgGr0.5) 50% and W50% in weight) called a silver-graphene tungsten composite material.
In accordance with one illustrative embodiment of the present invention, a circuit breaker comprises a first contact tip and a second contact tip. The first contact tip comprises a first electrical contact material comprising silver (Ag) and tungsten (W) and a first graphene material (Gr) having a range of 0.3% to 0.5% additively mixed in Ag with silver to form (AgGr)50W50 called a first silver-graphene tungsten composite material. The second contact tip comprises a second electrical contact material comprising silver (Ag) and tungsten (W) and a second graphene material (Gr) having a range of 0.3% to 0.5% additively mixed in Ag with silver to form (AgGr)50W50 called a second silver-graphene tungsten composite material.
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 electrical contact materials that improve conventional electrical contact material performance in arcing erosion and arcing energy. A new composition material of silver-graphene, (AgGr) has been introduced. Its powder is produced chemically with Ag salt particles in-situ synthesized with graphene oxide (GO) through by chemically reduction in an aqueous solution. After hydrogen reduction, the powder form of (AgGr) is produced. Conventional Powder Metallurgy (PM) techniques and hot-extruding are employed to prepare (AgGr) composite contact material. The metallic analysis depicts a 2-D carbon matrix where graphene is uniformly coated with silver particles. The extremely high modulus and strength of the 2-D carbon material is an advantage. This composition of materials has been successfully tested in low power switches and relays showing better performance in terms of endurance and durability due to its higher hardness, better mechanical properties as well as better electrical properties. However, silver-graphene can't be applied in low voltage products directly in this form because the melting temperature is similar to the Ag contact material. Testing in our applications in low voltage circuit breakers have been unsuccessful with (AgGr). Up to this point silver refractory metals have been the choice for arcing contact materials use in high fault current applications. These applications include low voltage molded case circuit breaker for residential and industrial applications. In response to this, a novel powder (AgGr) was created to form an advanced silver-graphene composite refractory material when combined with tungsten. Utilizing the PM process, silver-graphene-tungsten (AgGr0.3)W50 and (AgGr0.5)W50 contact tips were successfully produced. The PM process (press, sinter, and re-press) is the same process to make AgW50 contact tips. The microstructure and SEM images from fractography indicate the composite does not only inherit the characteristics of the conventional composite materials but also retains advanced characteristics of silver-graphene composite material. The composite materials of these two electric contact tips are silver-graphene bases, denoted as AgGr0.3% (Ag 99.7% and Gr0.3% in weight) and AgGr0.5% (Ag 99.5% and Gr 0.5% in weigh and mix with tungsten to form (AgGr0.3)W50 ((AgGr0.3)50% and W50% in weight) and (AgGr0.5)W50 ((AgGr0.5) 50% and W50% in weight). This invention examines properties, microstructures of cross-section, SEM images and preliminary test results including erosion life and standard electrical tests test in comparison with the conventional material AgW50 (Ag 50% and W50% in weight). Please note the brackets applied above is to explain the components of composite material and its percentage in weight. For clarity we omit the brackets, but it does not reflect any change in the composite material defined above. Embodiments of the present invention, however, are not limited to use in the described devices or methods.
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.
These and other embodiments of the silver-graphene tungsten material electrical contact tips of a low voltage circuit breaker according to the present disclosure are described below with reference to
Consistent with one embodiment of the present invention,
A unique 2-D graphene structure 125 has been inherited by a silver-graphene composite material (AgGr). A (AgGr)50W50 microstructure 130 has uniform mixing while tungsten (W) 117 distributes in a silver-graphene matrix 127. The contact tip 107 is produced utilizing a PM process 132 (press, sinter, and re-press). A (AgGr)50W50 based contact tip structure exhibited a total mass loss of 3.8% in a testing process. Arcing energy was reduced by 27.1% and 7.4% when testing at 5 kA and 65 kA respectively in a functional testing process.
Referring to
Two silver-graphene tungsten refractory composite materials, AgGr0.3W50 and AgGr0.5W50 have been described. Both materials have been examined in mechanical and electrical properties in comparison with conventional material AgW50. To better understand the novel materials, the metallurgical analysis explored their unique structure. Initial functional testing programs were conducted. Also, an additional erosion life test was completed and reported the percentage of mass loss. The results can be summarized as following.
The silver-graphene tungsten, AgGr0.3W50 and AgGr0.5W50 composite materials have shown their higher hardness while their resistivities and densities remain the same as with AgW50. The hardness increase has resulted in less percentage of mass loss during the erosion life test. Silver-graphene tungsten has been produced by a PM process successfully and the technology could be extended to the other popular composite materials, such as AgWC, AgC, CdO, SnO2, and NiO with graphene additive. 2-D graphene has dramatically improved silver-graphene composite material properties. The metallurgical analysis has been verified that silver-graphene tungsten composite materials also inherited 2-D graphene characteristics. The relative lower arcing energy has been reported by the test with AgGr0.5W50 material during high and low short circuit interruption, endurance, and the erosion life test. It will improve the performance in welding resistance, arcing erosion, and short circuit interruption.
Graphene (Gr) is a 2D carbon material that has been recognized by its excellent higher hardness and strength properties. The hardness difference between three composite materials, AgW50, AgGr0.3W50, and AgGr0.5W50 is measured by Vickers HV scale. The control material has Ag powder without graphene while the other two have Ag with graphene at 0.3 and 0.5% of weight respectively. The mean value of hardness of AgW50 is 161.6 HV while Ag50Gr0.3W50 and AgGr0.5W50 are 181.34 HV and 195.7 HV respectively. The increased mean hardness value is about 12% with AgGr0.3W50 and 21% with AgGr0.5W50 in comparison with AgW50. Meanwhile, there is no overlap of intervals between AgW50 and AgGrW50, which distinguishes the effect of graphene. Higher hardness of silver graphene materials with values up to 75 HV has been reported. Silver-graphene have much higher hardness than that of most particle-reinforced Ag contact materials. Therefore, the high strength and modulus of mechanical properties of silver-graphene should be inherited in AgGr0.3W50 and AgGr0.5W50 as well.
The measured resistivities of AgW50, AgGr0.3W50, and AgGr0.5W50 of all three materials are almost identical. Silver-graphene exhibits a very low resistivity of 1.6μΩcm compared the much higher resistivity of tungsten which may explain the similarity of the contact material resistivities. Like the resistivity, the densities of all three materials are very similar. The small percentage by weight of the graphene additive has a negligible effect on the density.
Turning now to
The interesting properties of silver-graphene tungsten had a direct effect on erosion over the life of the contact. An available ON and OFF operating equipment was setup to run 50,000-cycling operations with a circuit of 20 A and 220V AC to evaluate the performance of AgW50, AgGr0.3W50 and AgGr0.5W50 composite materials. All testing parameters are summarized in the Table 1. The arcing energy data was collected during the cycling testing and plotted in
A tester as an electrical contact operating system includes a power bank in the cabinets and an analog device standing on the cabinet. The testing samples include movable contact and static contacts, which are both (Ø5 mm×1.32 mm) from the electrical contact samples prepared for functional test in the following report. For this test, the contact material system was symmetric with both sides being made from the same material. Both contacts were soldered to “T” shape copper posts and then mounted the copper posts on the tester.
Based on statistical analysis, as shown in
In
To evaluate the performance of the silver-graphene tungsten composite materials based on the standard criteria, only two materials, AgW50 and AgGr0.5W50 are selected for these programs in order to reduce the tasks. A circuit breaker rated 100 A, 3 pole, plug-in type was selected to conduct all testing. The movable and stationary electrical contacts with the geometries (7.58 mm×5.08 mm×1.97 mm) and (9.59 mm×6.03 mm×1.32 mm) respectively are installed in these breakers. The contact system for all samples use one of conventional arrangement or material symmetric system. Four basic testing programs were planned in the matrix of Table 2.
First row of Table 2 is A-seq with six times rated overload test and then examine 100% rated temperature rise at 40° C. ambient after 50 ON and OFF operations. Second row is B-seq endurance test that includes 6,000 ON and OFF operations with 100 amps loaded and then 4,000 ON and OFF operations without load. Third row is C-seq with multiple 5 kA 240V short circuits, and last row is multiple high interruption current (HIC) ability test, D-seq at 65 kA 240V short circuits. Each testing program includes three samples of the same size as the minimum population.
A-seq results indicate the median temperature rise measured on the connectors from end to end of the samples were 40° C. for the AgW50 contact material and 41° C. for the AgGr0.5W50 material. All three samples with contact material of AgGr0.5W50 passed the B-seq test described in Table 2. In comparison with the samples with AgW50 only partially passed the tests. Silver-graphene tungsten material contributed to the successful testing due to its higher mechanical hardness property and its strength and durability.
AgGr0.5W50 composite material also has shown its better interruption performance in Table 3.
Testing with equivalent closing angles in C-seq, the samples with AgGr0.5W50 material resulted in a reduction of over 27.1% Pt in comparison with the samples with AgW50. This result not only shows its excellent interruption capability but also reduces arcing erosion and welding probability. This result may explain how the 2-D graphene structure matrix aids to preserve the composite structure together during interruption.
Data of D-seq in Table 3 has presented a small Pt reduction with 7.41%. However, it is inconclusive given the limited sample size. The percentage differences in duration and peak current are smaller and could be statistically equal in performance. For the duration the average time has slightly increased for silver-graphene tungsten. A larger testing sample may confirm if there is any difference for HIC testing for these materials.
After producing AgGr0.3W50 and AgGr0.5W50 contact tips by PM process as well as AgW50 as a control samples, three groups of the samples were subject to metallurgical analysis. The samples were cut and polished and then examined using an optical microscope to obtain microstructure photos. Three microstructures of the cross-section of the silver-graphene tungsten and silver tungsten are presented in
The microstructure images of silver tungsten in
The contact samples were mechanically sheared. The purpose of fracturing the contacts was to analyze the primary structure difference between materials. The fractography of three composite materials were characterized by SEM, as shown in
The structure of silver-graphene tungsten may explain its higher strength. It could explain how silver-graphene tungsten is being reinforced. The red circles indicate how the tungsten particles nest in the dimples.
A unique 2-D graphene structure has been inherited by a first silver-graphene composite material (AgGr) and a second silver-graphene composite material (AgGr). A (AgGr)50W50 microstructure has uniform mixing while tungsten (W) distributes in a silver-graphene matrix. The first contact tip 2307(1) and the second contact tip 2307(2) are produced utilizing a PM process (press, sinter, and re-press). A (AgGr)50W50 based contact tip structure exhibited a total mass loss of 3.8% in a testing process. The arcing energy was reduced by 27.1% and 7.4% when testing at 5 kA and 65 kA respectively in a functional testing process.
While silver-graphene tungsten is described here a range of one or more other composite materials are also contemplated by the present invention. For example, other popular composite materials, such as AgWC, AgC, CdO, SnO2, and NiO with graphene additive may be implemented based on one or more features presented above without deviating from the spirit of the present invention.
The techniques described herein can be particularly useful for AgGr0.3W50 and AgGr0.5W50. While particular embodiments are described in terms of AgGr0.3W50 and AgGr0.5W50, the techniques described herein are not limited to such a 0.3% or 0.5% but can also be used with other graphene percentages.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
