Device with an active stabilizer for improving electrical contact connections and method of use

Abstract

A device for improving electrical contact, using copper-based shape memory alloy components, to regulate and optimize the contact pressure in an electrical connection. This device consists of conductive contact elements, threaded connections and an active stabilizer made of copper-based shape memory alloy wires, which can have configurations such as a mesh, lattice or porous metal material, providing a wide surface coverage. The unique property of the active stabilizer allows it to adjust the contact pressure at micro-levels when overheating occurs between the conductive elements. The active stabilizer improves the contact connection and reduces residual deformation. Additionally, an electrically conductive lubricant is introduced, consisting of a semi-liquid lubricant and burrs of shape memory alloy powder, which improves conductivity, minimizes oxide formation and provides sealing against contaminants. This improves electrical contact stability, extends the life of the connection, and provides adaptive properties to maintain optimal contact conditions under varying electrical loads and environmental conditions.

Description

DEVICE WITH AN ACTIVE STABILIZER FOR IMPROVING ELECTRICAL CONTACT CONNECTIONS AND METHOD OF USECOPYRIGHT NOTICE

[0001] Part of the disclosure of this patent document contains material subject to copyright protection. The copyright owner has no objection to facsimile reproduction of this patent document or to the disclosure of the patent contained in the patent file or in the records of the Patent and Trademark Office, but retains all copyrights in full.FIELD OF TECHNOLOGY

[0002] The invention relates to a new device comprising an active stabilizer with an improved electrical contact connection, such that the contact connection maintains excellent conductivity during operation, resulting in increased efficiency and reliability. The new device with an improved electrical contact connection according to this invention can be used in the electric power, oil and gas, metallurgical, mining, chemical, and related industries, as well as in transportation, networks, and electric traction transport systems for installation in substations, switching devices, and other electrical installations. The device with an improved electrical contact connection according to this inVention is suitable for receiving, converting, and distributing electrical energy in networks in the voltage range up to 1000 V and above.STATE OF THE ART

[0003] More specifically, the invention is aimed at reducing the contact resistance of detachable electrical connections of current-carrying elements, also known as detachable bolted electrical connections (hereinafter referred to as DBEC). The device enables the direct connection of contact parts made of copper, aluminum, and their alloys during installation, repair, and maintenance of existing electrical equipment, as well as in the manufacture of electrical equipment based on functional intermetallic compounds.

[0004] The primary function of electrical contact devices is to connect individual elements of an electrical installation and to create standardized conditions under which electrical contact connections ensure maximum reliability and minimal electrical energy losses over the required period. Consequently, the continuous, uninterrupted, and efficient operation of electrical equipment depends on the physical and chemical processes occurring in electrical contact connections.

[0005] During the operation of electrical equipment, contact connections are periodically heated by electric currents in accordance with the electrical load profile or by short-circuit currents. The heating and cooling processes of contact connections lead to an increase in mechanical stress in the contact parts, the accumulation of residual deformation, a decrease in contact pressure, an increase in transient contact resistance, and, as a result, an undesirable rise in heating temperature at the same load currents and excessive electrical energy losses.

[0006] The increase in mechanical stress in the contact connection as the temperature rises occurs because the current-carrying parts (material — aluminum and / or copper) and the fasteners (steel) have different coefficients of thermal expansion. In this case, the accumulation of residual deformation in the conductive contact parts leads to a decrease in contact pressure and, consequently, to a reduction in the number and area of contact pads between the contacting surfaces. Furthermore, due to the existing roughness (micro-roughness) of the contact surfaces, the reduction in the number and area of contact pads occurs unevenly across the contact connection area. This results in the initial heating stage of the contacting surfaces developing unevenly across the entire contact area.

[0007] The process of contact overheating during prolonged operation is natural and inevitable from a physical standpoint and can be reversed only through the use of additional measures. In the absence of additional measures and designs that allow for the reduction of electrical contact overheating through continuous temperature monitoring with automatic contact pressure regulation, sealing of the inter-contact space, and removal of oxide films, overheating and thermal destruction of the contacts are inevitable. And this leads to at least partial or complete failure of the electrical installation. All electrical contacts in electrical installations are subject to thisphenomenon. Ultimately, the failure of electrical contacts is one of the main causes of reduced efficiency in electrical installations as a whole.

[0008] Another important factor in improving the reliability of a contact connection is stabilizing the contact pressure force at a specified nominal level across the entire area of the electrical contact connection. The nominal value of the applied contact pressure force depends on the type of metal or alloy of the conductive parts (aluminum and / or copper) used and their hardness. A reduction in the applied contact pressure force, which may occur at any micro-level across the contact surface, to a value below the nominal level leads to an increase in contact resistance and a rise in contact heating temperature.

[0009] Various types of electrical connections can be used in electrical networks and electrical equipment. The most common of these are detachable bolted electrical connections (or DBECs), as shown in Figure 1. The effective operation of electrical networks and electrical equipment depends to a large extent on the reliability and efficiency of the numerous DBECs connecting individual sections of electrical networks and electrical equipment.

[0010] As mentioned above, the problem of DBECs aging, which affects the reliability and efficiency of electrical networks and electrical equipment, lies in the uncontrolled and uncompensated increase in contact resistance. This leads to additional power losses and overheating of contact elements, which can result in accidents, fires, and power outages, requiring significant time and financial costs.[Oil] In general, the factors influencing the increase in the contact resistance of DBECs are:• accumulation of residual deformation in the DBEC elements during heatingcooling cycles due to the use of materials with different coefficients of thermal expansion (for conductive parts: aluminum and / or copper, and for fasteners — bolts and nuts: iron and / or steel);• a decrease in contact pressure, for example, when the connection loosens due to the accumulation of residual deformation in the conductive elements caused by periodic heating and cooling or vibration;• oxidation of the surfaces of the conductive elements of the contact connection due to the formation of dielectric oxide films caused by the penetration of air and moisture into the inter-contact space;• uneven reduction in the number and area of micro-contact regions due to the roughness of the contact connection surfaces, as well as• a decrease in contact pressure and an increase in the temperature of the contact connection contribute to the intensification of oxidation processes in the conductive parts of the contact connection, etc.

[0012] Several methods have been proposed to prevent a decrease in contact pressure using contact pressure stabilizers in the form of Belleville washers. The known contact connections described in RU2091932 Cl include, in particular, contact terminals. RU2091932 Cl proposes a threaded connection with a bolt and nut to clamp the contact tips and at least one Belleville washer made of an alloy with a superelastic effect, which provides some control and regulation of contact pressure. However, when the contact pressure drops below 30%, this stabilization method becomes ineffective due to the thermomechanical properties of superelastic alloys, leading to contact degradation due to overheating and overall electrical energy loss.

[0013] A contact connection is also known, described in UA57110 C2 and W02023060325 Al, comprising a bolt with a nut for clamping the contact elements and two contact pressure stabilizers in the form of conical washers. According to UA57110, one stabilizer is made of an alloy in which the shape memory property manifests itself in the temperature range from -40 to +200°C, while the other stabilizer exhibits superelasticity in this temperature range. The presence of two stabilizers with different properties eliminates the shortcomings identified in RU2091932 Cl. However, this method does not solve the problems mentioned above, since the shape memory alloy (SMA) stabilizer has thermal inertia. Furthermore, this stabilization method does not provide a rapid response to the heating of individual micro-levels of the contacting surfaces of the conductive parts, which does not solve the problem of degradation of the applied force and subsequent failure of the contact connection.

[0014] US9093778 B2 describes a contact connection comprising contact elements, a threaded connection with a bolt and nut for clamping the contact parts, andat least one additional conductive element incorporated into the structure prior to the bolted connection. The inserted conductive element is a metal plate element with a porous metal structure. During installation of the contact connection, the porous plate compresses, filling in the irregularities of the rough surface of the contact parts and ensuring the nominal contact resistance at the time of installation. However, the inserted conductive element does not ensure stabilization of contact pressure and contact resistance during operation, as it lacks elastic or thermoelastic properties. When the temperature rises, the material can expand only to a limited extent, which is insufficient to stabilize the contact pressure. This element also does not ensure the removal of oxide layers on the contact surfaces during the operation of the electrical installation.

[0015] UA79134 C2 describes a contact connection comprising contact elements, a threaded connection with a bolt and nut, and at least one contact pressure stabilizer associated with the bolted connection. The contact pressure stabilizer is a shapememory alloy plate installed between the contact parts and corresponding to the contact area, which initially has a sinusoidal shape. When the contact connection is installed to the nominal contact pressure, the plate assumes a flat shape. However, the periodically varying load current causes the contact connection to heat up and cool down, leading to the accumulation of residual deformation in the conductive parts, a decrease in contact pressure, and an increase in contact resistance, as well as further undesirable heating of the electrical contact connection. When the contact connection heats up above the temperature at which the plate alloy begins to undergo elastic deformation, it tends to restore its sinusoidal shape and simultaneously develops a reactive force. By changing its shape, the plate only partially destroys the oxide films on the surface of the contacting parts, which is insufficient to slow down the chemical aging process of the contact connection. This technical solution does not allow for stabilizing contact pressure in the area of individual micro-levels of the contact surfaces, which leads to overheating of the entire contact connection.

[0016] All known technical solutions that propose the use of a threaded electrical contact connection with a bolt and nut to clamp the contact parts do not provide a comprehensive and effective solution to the problem of physical and chemical agingof electrical contacts. Previous solutions do not ensure complete and effective stabilization of contact pressure and contact resistance during operation, nor do they ensure stabilization of contact pressure in individual micro-regions of the contact surfaces, which leads to overheating of the entire contact connection. Previous solutions do not prevent and / or eliminate the formation of oxide films during the operation of electrical equipment. Thus, to date, there are no known comprehensive solutions that ensure the reliable and effective operation of DBEC.

[0017] We offer a unique integrated solution that neutralizes all the negative factors discussed above by creating an electrical contact device containing an active stabilizer made of a shape-memory alloy, which ensures effective stabilization of contact pressure and contact resistance. It responds to thermal radiation from individual micro-levels across the entire surface of the contact connection and is regulated by direct heating with an electric current, acting as a conductive element in the contact connection. A device containing an active stabilizer eliminates overheating of the contact connection and prevents its thermal degradation. The device additionally includes means for monitoring and detecting overheating of the contact connection, as well as means for breaking down oxide layers on the contact surfaces during normal operation. This ensures optimal electrical conductivity between the contact surfaces of the connection, reduces additional power losses and maintenance costs, and extends the service life of all electrical contact connections.BRIEF DESCRIPTION OF THE INVENTION

[0018] The proposed invention is a device comprising a detachable contact connection and an active stabilizer made of a shape-memory alloy based on copper. The proposed contact connection has improved electrical contact, thanks to which the contact maintains excellent conductivity during operation, leading to increased efficiency and reliability of the entire electrical system. The proposed device also allows for a reduction in the contact connection’s transient electrical resistance, which reduces overall electrical energy losses during operation. Furthermore, the deviceeliminates the increased heating of the contact connection during operation, which leads to a deterioration in the electrical contact’s performance.

[0019] The device comprises at least two conductive contact elements with contact surfaces, at least one threaded connection with a threaded element, and at least one nut for clamping the contact surfaces of the conductive elements. In addition, the device comprises at least one active contact stabilizer, wherein the stabilizer is an element made of a shape-memory alloy.

[0020] The active stabilizer according to this invention is made of a copper-based intermetallic material, which may be a alloy, a grid, a porous metal material, or interwoven metal wire. A alloy of copper-based shape memory alloy wire may be multilayered and adapted in geometric dimensions for placement between the contact surfaces of the conductive elements of an electrical contact connection, and its area corresponds to and is at least equal to the contact surface area of the contact parts.

[0021] An active stabilizer based on a copper shape-memory alloy, which actively (due to the current flowing through the contact micro -pads and the stabilizer) regulates the contact pressure between the conductive contact surfaces during operation and is designed to maintain this pressure at a nominal level in the event of residual deformation accumulation in the contact parts and a decrease in contact pressure, which leads to an undesirable increase in the temperature of the electrical contact connection. The operation of the active stabilizer is based on the thermodynamic properties of intermetallic compounds.

[0022] Furthermore, a copper-based active stabilizer is typically used in the form of a alloy made of shape-memory alloy wire, arranged as a stacked or layered package, which allows for an increased contact area at a greater number of points along the conductive parts, thereby maximizing conductivity across the micro-levels. This increase in the contact area between the contact surfaces and the reduction in contact resistance allows for a reduction in the heating temperature of the contacts within the device and prevents electrical energy loss and rapid oxidation of the contacting surfaces.

[0023] The active stabilizer — a copper-based wire alloy according to this invention — is a material selected from the group of alloys: Cu-Al-Mn, Cu-Al-Zn, Cu-Al-Ni, and Cu-Al-Fe. In the most preferred embodiment, the copper-based alloy material is a Cu-Al-Mn alloy containing 2-9% Mn and 10-13.5% Al, more preferably 4—6% Mn and 11.5-12.5% Al, with the most preferred composition being 5% Mn, 12% Al, and the remainder consisting of Cu and impurities.

[0024] A copper-based wire alloy made of a shape-memory alloy may be coated or galvanized with at least one coating of copper, tin, silver, indium, and their alloys to reduce the formation of oxide films on the surface of the contact parts.

[0025] The Cu-Al-Mn alloy is critical to the effectiveness of the active stabilizer according to this invention. It has minimal electrical resistance, thereby ensuring optimal energy transfer. In addition, its high thermal conductivity ensures rapid heat dissipation, particularly between the austenite phase at an initial temperature of 5°C (As) and the austenite finish temperature of 90°C (Af), where the range is predominantly between 40 and 70°C, where Af denotes the maximum possible transition temperature of the Cu-Al-Mn alloy.BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Fig. 1 shows a general view of a detachable contact connection of two flat busbars, known from the prior art.

[0027] Fig. 2 shows a diagram of the radial distribution of mechanical stresses in the plane at the contact zone between two contact parts known from the prior art.

[0028] Fig. 3A shows an enlarged perspective view of the electrical contact connection prior to connection by pressing.

[0029] Fig. 3B shows an enlarged perspective view of the electrical contact connection after connection by pressing and a cross-section thereof.

[0030] Fig. 4 A shows a general view of a detachable contact connection of two flat electrical busbars with an active contact pressure stabilizer and a contact overheating temperature indicator according to this invention.

[0031] Fig. 4B shows an example of a alloy made of shape memory alloy wire used to manufacture the contact pressure stabilizer.

[0032] Fig. 5 shows an enlarged cross-section of the contact connection with the stabilizer installed between the conductive parts of the busbar contacts.

[0033] Fig. 6 shows the thermomechanical hysteresis in the shape-memory alloy, depicting the critical temperature points of thermomechanical transformations during heating and cooling, as well as the corresponding temperature range of thermomechanical hysteresis.

[0034] Fig. 7 illustrates the functionality and operational stages of the contact pressure stabilizer, showing its uncompressed and compressed states, as well as its interaction with the conductive parts.

[0035] Fig. 8 shows the deformation and recovery processes of the stabilizer in a contact joint, its various states, and highlights the role of reactive forces.

[0036] Fig. 9 shows the functional block diagram of the experimental test bench.

[0037] Fig. 10 shows the thermomechanical part of the test bench, highlighting the interrelationship of the main components.

[0038] Fig. 11 shows the thermomechanical properties of a copper-based shape memory alloy wire.

[0039] Fig. 12 shows experimental graphs of changes in compressive force at a temperature of 70°C in a contact joint with a stabilizer, which correlate with various degrees of deformation of the stabilizer.

[0040] Fig. 13 shows the deformation characteristics of the shape memory alloy at temperatures exceeding the As temperature for reverse martensitic transformation, highlighting the regions of elastic and superelastic deformation in the forward and reverse directions.

[0041] Fig. 14 shows a functional block diagram of the experimental setup, detailing the thermoelectric unit, the data acquisition and storage unit, as well as various associated components, including the shape memory alloy material.

[0042] Fig. 15 shows the thermo-force section of the test rig, designed for testing thermo-sensitive shape memory alloy elements.

[0043] Fig. 16 shows the dynamic change in the thermomechanical force of a 0.1 mm diameter wire made of a copper-based shape memory alloy when heated by an electric current.

[0044] Fig. 17 is a graph of the dynamic change in the resistance of the contact connection of aluminum busbars over time during periodic manual reduction of the main contact pressure.

[0045] Fig. 18 is a graph showing the temperature jump over time of an aluminum busbar contact connection when the main contact pressure is periodically manually reduced.DETAILED DESCRIPTION OF THE INVENTION

[0046] Fig. 1 shows a general view of a detachable contact connection between two flat busbars known from the prior art. The figure shows an electrical contact assembly (100) having two conductive components (101, 102) integrated into the contact connection of the flat busbars. These components, made of a known conductive material (aluminum, copper, or alloys based on them), typically operate in a low-resistance environment and provide electrical power transmission.

[0047] Furthermore, the assembly (100) includes a bolt (103) that interacts with a corresponding nut (104) to provide a mechanical and electrical connection between the conductive elements (101, 102). Tightening the nut (104) improves the electrical connection in the assembly (100) and ensures standardized contact pressure and contact resistance.

[0048] The connection (100) also includes steel flat washers (105, 106) that ensure a more uniform distribution of pressure across the contact connection plane.

[0049] During operation, under the influence of electric current and heat generated in the contacts, interaction with the environment (air, moisture, and the presence of aggressive impurities), physical and chemical processes occur in the connection structure (100), leading to an increase in electrical resistance and a rise in the temperature of the contact connections. Over time, these processes lead to the accumulation of residual deformation in the conductive elements, a decrease in contact pressure, a further increase in contact resistance, and overheating of the contact in a continuous cycle.

[0050] Heating of the contact surfaces across the plane is uneven. The points where the contact surfaces of the current-carrying elements and the stabilizer meethave a higher temperature during overheating. When the temperature of the areas with higher heating reaches a temperature higher than the temperature at which the stabilizer’s alloy pack begins to regain its shape, the stabilizer locally regains its original shape, thereby increasing the stabilizer’s dimensions in the transverse direction. Another operating mode of the stabilizer is associated with sharply increasing currents. In this case, the stabilizer ensures optimization of contact pressure due to its internal (direct) heating by an electric current.

[0051] Fig. 2 is a detailed diagram illustrating the radial distribution of mechanical stresses across the contact plane. The diagram shows two conductive elements (201, 205), which are an integral part of the contact connection. These parts, made of common conductive materials, form the basis for the transmission and distribution of electrical energy.

[0052] The conductive parts are connected using a bolt (203) and a nut (202) as part of the connection (200). Together, the bolt and nut secure the busbar connection, and when the contact connection is installed using a wrench, they ensure the specified contact pressure. In addition, to ensure uniform distribution of the mechanical load when tightening the nut, a washer (204) is provided, which prevents direct mechanical contact between the bolt head and the surface of the contact part and reduces local stress concentration.

[0053] Fig. 3 A shows an enlarged view of the electrical contact from the prior art prior to the application of pressure. The drawing shows two conductive elements (301, 302) necessary for forming a contact connection. A notable feature of these elements is their uneven surfaces (303), clearly highlighted in the enlarged cross-section. These uneven surfaces, prior to the application of pressure, highlight the possibility of uneven contact, which then leads to the transmission of electrical energy through areas with good contact (the surfaces of the contact parts in these areas are compressed with a standardized force) and low contact resistance.

[0054] Fig. 3B — an enlarged perspective view of an electrical contact from the prior art after pressure is applied. The drawing clearly shows the contact zones (304) between the two conductive parts, the area and number of which increase under pressure as the nut is tightened. In addition, the figure shows contact points betweenthe two conductive parts with concentrations of electric current lines (305) that form due to uneven contact across the contact area. The uneven distribution of electric current across the contact area leads to uneven heating of areas on the contact surface.

[0055] Figs. 3A-B, taken together, show the transition of contact zones under varying pressure conditions, which leads to uneven contact and, consequently, to additional power losses in the contacts due to their heating. When conditions arise that reduce contact pressure (for example, due to periodic heating and cooling of the contact connections during changes in electrical load currents and the accumulation of residual deformation in the contact parts), the number and total area of the contact zones decrease. At the same time, current concentration and contact resistance increase, leading to an undesirable rise in heat generated in the electrical contact.

[0056] Fig. 4A is a perspective view of an electrical contact according to the present invention; it shows a device (400) having two flat busbars, complete with a contact pressure stabilizer and a contact overheating thermal indicator. The main elements of this device (400) are the conductive parts (401, 402), which form the basis for the transmission of electrical energy, the thermal indicator (406), and the stabilizer (407). These are complemented by washers (403, 408), which help evenly distribute the mechanical load from the bolted joint (bolt and nut).

[0057] A distinctive feature of this device is the bolt (404) and nut (405) system. The bolt head (409) and hole (410) provide a reliable mechanism for holding the conductive parts and stabilizer (407) in place and ensure a secure connection. As a safety measure, a thermal indicator (406) has been incorporated; by changing the angle of inclination (relative to the plane of the tires) of the signal portion, it signals overheating of the contacts, allowing for timely preventive maintenance and ensuring the integrity of the system.

[0058] Fig. 4B shows an example of a shape-memory alloy wire alloy used to manufacture the contact pressure stabilizer (407). Made of a shape-memory alloy, this stabilizer provides the device with elastic and dynamic properties. It adapts to varying pressure conditions and helps maintain optimal contact pressure, increasing electrical conductivity and preventing damage due to overheating.

[0059] The integrated circuit, as shown in Figs. 4A-B, is an optimal solution that combines traditional bus elements with an innovative active stabilizer control mechanism for efficient energy transfer while prioritizing system durability.

[0060] Fig. 5 shows an enlarged cross-section of a contact connection equipped with a stabilizer located between the conductive elements. The contact system includes conductive parts (501, 504) that form the basis of the contact connection; a stabilizer (502) is installed between them, which is a critical component that allows maintaining optimal contact pressure even under varying operating conditions. The force “F” denotes the compressive force acting on the conductive parts of the contact. The stabilizer, made of a shape-memory alloy, responds to direct heating by an electric current or to the heating of individual contact zones and provides localized regulation of contact pressure across the entire surface of the contact connection — stabilizing both contact pressure and contact resistance.

[0061] Our system includes a conductive lubricant (503) consisting of a semifluid oil with a thickener and a powder having micro-scratches on its surface and made of a shape-memory alloy (506). This strategic combination serves two functions: it minimizes oxide formation between conductive parts and optimizes electrical conductivity. The lubricant utilizes the unique properties of the shape-memory alloy to improve the electrical connection.

[0062] After installation and application of nominal pressure to the contact connection, the semi-fluid component of the grease penetrates the gap between the surfaces of the contact parts, thereby sealing the contact against moisture, air, and aggressive contaminants. At the same time, the powder particles in the grease fill the surface irregularities of the contact parts, undergoing deformation during the compression process when the contact connection is installed and thermal deformation of the contact parts as their temperature changes.

[0063] During the service life of the contact connection, the powder performs a dual role: first, by filling the surface irregularities of the contact parts, it increases the effective contact area, reducing contact resistance. Second, when the electrical load changes and causes thermal fluctuations in the contact connection, the powder particles (506), by changing shape, break down the oxide film on the contact surfaces.This action further reduces contact resistance, extending the service life of the contact connection.

[0064] The combination of an elastic pressure stabilizer and a specially formulated conductive powder lubricant, as shown in Fig. 5, creates an innovative solution for maintaining optimal electrical contact. The lubricant simultaneously improves electrical conductivity and increases the durability of the contact connection, making it a cost-effective design.

[0065] Fig. 6 is a graphical representation of the thermomechanical hysteresis curve of a shape memory alloy. The graph shows the main temperature thresholds at which phase transformations occur in the shape memory alloy, designated as As, Af, Ms, and Mf.

[0066] As and Af delimit the temperature range in which reverse martensitic transformation occurs during heating, initiating the formation of austenite. Conversely, Ms and Mf define the temperature range that catalyzes direct martensitic transformation during cooling, leading to the appearance of the martensitic phase.

[0067] Ap and Mp, respectively, denote the midpoints of these transformations, which allows one to understand the dynamics of phase transitions in the alloy under various temperature conditions.

[0068] The graph shows the temperature range in which thermomechanical hysteresis is observed, which once again underscores the temperature-dependent nature of the properties of shape memory alloys.

[0069] Fig. 7 - a detailed view of a system of stabilizing alloy-shaped packages stacked one on top of the other. The alloy package (701) - a stabilizer that is the central element of the device - is shown in the inactive state (702). The specially designed alloy structure is key to modulating the pressure applied to the contact surfaces.

[0070] The stabilizer plane shows the contact zones (703) between the two conductive parts, highlighting their importance for an effective electrical connection and the stabilizer’s active role in maintaining contact pressure.

[0071] The active stabilizer is shown in a compressed state (704), positioned between the two contact elements. This illustration highlights the stabilizer’s ability tomaintain constant contact pressure even with the slightest temperature fluctuations in the system, actively contributing to the overall efficiency of the electrical contact device. The roughness of the upper and lower surfaces of the active stabilizer indicates that it selectively fills the gaps in the contact surfaces, improving electrical contact and thereby reducing contact resistance. The active stabilizer expands in the transverse direction in response to an electric current or heating of local contact zones, stabilizing the contact pressure.

[0072] Fig. 8 shows the deformation process of the stabilizer in a contact connection and the corresponding directions of reactive forces during shape recovery. The stabilizer is shown at various stages, allowing for a more detailed examination of the complex interaction with the shape memory alloy (SMA).

[0073] Initially, the stabilizer (801) is in an uncompressed, free state. The stabilizer, made of a copper-based SMA, may have a cylindrical shape (802). The subsequent transformation of the stabilizer under the action of the compressive force “F” is shown in (803), allowing for a comparison of structural changes under mechanical loads.

[0074] Next, in Fig. 8, section (804) is an enlarged view of the compressed stabilizer. An important aspect here is the specified direction of the reactive forces acting during the shape recovery process. In this case, the reactive force Fl restores the wire’s original straight shape, while F2 restores the wire’s original circular crosssection. Together, forces F, Fl, and F2 interact with one another. As F decreases (with the accumulation of residual deformation in the contact areas), the concentration of electric current increases or local areas heat up, and the stabilizer tends to restore its initial shape, while forces Fl and F2 stabilize the contact pressure.

[0075] Fig. 9 — Functional block diagram of the experimental test bench device. The device is divided into two main segments: the thermo-mechanical unit (I) and the data display and storage unit (II), reflecting the synergistic relationship between thermo-mechanical processes, data collection, and data interpretation.

[0076] The thermo-mechanical unit consists of a regulated power supply (901), a heater (902), a wire (903) (SMA), and an alloy temperature sensor (905). A strain gauge (904) is provided to measure the deformation of the thermosensitive element(wire) (903), and a temperature sensor (905) is provided for thermal monitoring. This unit demonstrates the synergy between the individual components, focusing on the study of the thermomechanical properties of the SMA.

[0077] In parallel with this, the information display and storage unit serves as the digital interface of the device. Analog-to-digital converters (906, 907) digitize data in real time from the thermo-mechanical section. The microcontroller (908) processes this data and displays it on the touchscreen (909). An independent power supply (910) ensures reliable operation, and the memory device (911) archives the collected data for further analysis and review. This setup is a comprehensive digital system for collecting, displaying, and storing valuable experimental data.

[0078] Fig. 10 shows the configuration of the experimental thermomechanical test bench (results are presented in Table 1 below), on which the properties of shape memory alloy (SMA) thermo-sensitive elements were investigated. This setup includes a strain gauge (1001) for strain monitoring, clamping fixtures (1002) to ensure proper fixation of the test specimen, an SMA thermosensitive element (1003), a heater (1004), a temperature sensor (1005), and a glass flask (1006) for holding the sample of the thermosensitive SMA element. The results of experimental studies on the dependence of the reactive force of shape memory alloy elements on heating temperature are presented in Table 1.

[0079] Fig. 11 shows that a copper-based shape memory alloy wire with a diameter of 0.1 mm or more is capable of developing a maximum reactive force of 0.208H at temperatures up to +100°C, with a desired range up to a temperature of +70°C and a reactive force of 0.096H. Line 1 reflects the wire’s behavior during heating, and line 2 — its characteristics during cooling, demonstrating the material’s phase transformation properties.

[0080] Fig. 12 shows empirical graphs of the dynamics of the contact pressure change process for one of the possible operating modes of the stabilizer, illustrating changes in the clamping force of the contact parts in the presence of the stabilizer at a given temperature (+70°C). Fig. 12 shows the reactive force of the stabilizer (1) and the manually adjustable clamping force (2), which was changed discretely by 5 at the specified points (a, b, c, d, e).

[0081] In this case, a deformation of 5=100% corresponds to a fixed contact connection at the nominal force. A deformation of 5=0% corresponds to the compressive force on the contact parts when F=0. Superelasticity in the shapememory alloy stabilizer is observed (at temperatures above As, and in this example at +70°C) when the compressive force on the contact parts is manually and gradually reduced between points ‘a’ and ‘d’. Despite this reduction, the stabilizer maintains the nominal contact pressure up to the deformation point ‘d’, highlighting the superelastic properties of the alloy.

[0082] During operation, the contact pressure (generated by the bolted connection) decreases discretely due to periodic thermal loads from short-circuit currents or the load, as well as the subsequent accumulation of residual deformation in the contact elements. This behavior is consistent with the previously discussed case of manually induced pressure reduction.

[0083] Fig. 13 shows the deformation behavior of an SMA alloy wire at temperatures above the As temperature (the onset of reverse martensitic transformation). It illustrates three main regions: elastic deformation (1), superelastic deformation (2), and superelastic deformation in the reverse direction (3), highlighting the unique thermomechanical properties of SMA.

[0084] Fig. 14 shows a functional block diagram of the experimental setup, consisting of a thermo-mechanical section (I) and an information display and storage unit (II). It contains various components, including a regulated power supply (1401), a thermosensitive SMA element (e.g., wire) (1402), a strain gauge (1403), a current sensor (1404), A / D converters (1405, 1406), a microcontroller (1407), a touchscreen (1408), a power supply (1409), and a data storage device (1410).

[0085] Fig. 15 shows the thermoelectric section of the experimental setup designed to study the characteristics of SMA thermoelectric elements. The main components include a strain gauge (1501), insulating mounts (1502), a thermosensitive SMA element (e.g., wire) (1503), a copper strip (1504), and a current sensor (1505).

[0086] Fig. 16 shows the change in the thermomechanical force of a copper-based shape memory alloy wire with a diameter of 0.1 mm or greater over time under theaction of electrical currents of varying magnitudes: 0.15 A, 0.23 A, 0.28 A, 0.46 A, 0.55 A. Fig. 16 illustrates the dynamics of thermomechanical processes during direct heating. The graphs show that when the wire is heated directly by an electric current, the shape recovery time is in the order of thousandths or hundredths of a second. When the stabilizer is activated in problematic contact zones with increased contact resistance, synchronous stabilization of contact pressure and a synchronous reduction in contact resistance occur, thereby preventing the heating of the entire contact connection area. Through indirect influence, the active stabilizer significantly slows down the physicochemical aging processes of contact connections.EXAMPLES OF WORK

[0087] Example 1

[0088] We conducted experimental studies of the properties of copper-based SMA alloy wire (diameter 0.1 mm or greater) on a test bench, as shown in Figs. 9 and 10. Table 1 (together with the graph in Fig. 11) presents the results of experimental studies of the dependence of the reactive force of shape memory alloy wire on heating temperature.Table 1. Experimental data on the thermomechanical characteristics of a wire made of Cu-Al-Mn alloy (diameter 0.1 mm)Temperature, °C 20 30 40 50 60 70 80 90 100 (heating)Reactive force, H 0 0 0.004 0.01 0.052 0.096 0.164 0.202 0.208Temperature, °C 100 90 80 70 60 50 40 30 20 (cooling)Reactive force, H 0.208 0.208 0.208 0.206 0.2 0.152 0.092 0.041 0.013

[0089] Based on the alloy or grid design (as shown in Fig. 4B), there are 36 deformation nodes (wire intersections in different directions) per 1 mm2. In the first experiment, using the test rig shown in Fig. 10, the wire was deformed in a maimer analogous to its deformation in a contact connection between two flat electrical busbars at a temperature below +40°C.

[0090] Upon further heating of the wire above a temperature of +40°C, its initial shape is restored and a force appears, distributed over an area of 1 mm2, F = 36 x 0.202 = 7.3H at a temperature of 90°C and F = 36 x 0.096 = 3.5H at a temperature of 70°C (Table 1, Fig. 11).

[0091] In the case of a contact connection between two flat aluminum busbars measuring 60 mm in width and 6 mm in thickness, it is recommended to set the length of the contact connection (the length of the contact surface of the busbars) to 60 mm. Thus, the contact area in this case will be 3,600 mm2. A single M12 bolt, a nut, and two flat steel washers were used to connect the busbars. The nominal contact force was 12,000H. The specific normal force (or contact pressure) per 1 mm2will be F = 12,000 / 3,600 = 3.33H.

[0092] Comparing the nominal data for the specific force on the plane in the contact connection (3.33H), the experimentally obtained thermomechanical characteristics of the wire (maximum force - 0.202H) and the force during alloy shape recovery (1 mm2- 3.5H at 70°C), a positive conclusion can be drawn that the stabilizer develops sufficient force to regulate the pressure in the contact joint in accordance with the specified conditions.

[0093] The number of grids (alloyes) in the stabilizer assembly is determined by the standard sizes of bolted connections with the following thread pitches: M6 - 1.00 mm; M8 - 1.25 mm; M10 — 1.50 mm; M12 — 1.75 mm; M14 and M16 - 2.00 mm. Furthermore, through experimental studies, we have established that the alloy stack deforms in the transverse direction by a maximum of 25% of the total transverse thickness of the stack in its initial state, with the wire alloyes having been laid out and measured.

[0094] Table 2 presents the calculated number of alloyes (grids) in the stack required for various sizes of bolted joints. The invented SMA active stabilizer, containing a stack of wire alloyes, ensures stabilization of contact pressure when gaps occur equivalent to at least 25% of the thread pitch of the bolted joint.Table 2. Results of calculating the number of grids (grids) in a package for different sizes of bolted connectionsSize Thread pitch, mm Minimum Minimum number of grids stabilization in a package, pcs. clearance, mmM6 1.00 0.25 5M8 1.25 0.31 6M10 1.50 0.37 8M12 1.75 0.45 9M14 2.00 0.50 10M16 2.00 0.50 10

[0095] Example 2

[0096] A significant difference between the claimed invention and the prior art is also that the arrangement of the shape-memory alloy alloy pack between the contact surfaces provides not only indirect heating of the stabilizer from the contacting parts, but also direct heating by means of an electric current passing through the alloy pack (in a direction transverse to the alloy).

[0097] Using a test bench, the functional block diagram and thermal -mechanical section of which are shown in Figs. 14 and 15, respectively, experimental studies were conducted on the shape recovery dynamics of a 0.1 mm diameter Cu-Al-Mn alloy wire under direct heating by electric currents of 0.15 A, 0.23 A, 0.28 A, 0.46 A, and 0.55 A, respectively; the corresponding graph is shown in Fig. 16.

[0098] When the stabilizer wires are directly heated, depending on the current magnitude and the rate of its increase over time, the restoration of the stabilizer’s shape occurs almost simultaneously with the increase in electric current. In this case,the stabilizer heating process can be called adiabatic due to a short period of rapid internal heating without heat loss.

[0099] When the stabilizer grids are directly heated by an electric current, the stabilizer’s reactive force increases rapidly. In response, the contact pressure of the connection also increases synchronously. This effect prevents overheating of the contacting parts, since the operation of the active stabilizer and the reduction of contact resistance can occur in a fraction of a second.

[0100] A distinctive feature of the active stabilizer according to this invention is that it is activated when the microstructures are heated to temperatures below the permissible limit for aluminum or copper contact parts, thereby actively preventing overheating of the entire contact connection and significantly slowing down the aging process of the contact connection. Consequently, this property enhances the durability and operational efficiency of the connection.

[0101] Example 3

[0102] The stabilizer is made of copper-based SMA wire with a diameter of 0.1 mm or greater. The woven alloy is formed as shown in Fig. 4B. Changes in contact resistance and temperature were compared in three variants of contact connections for flat aluminum busbars with a cross-sectional area of 60x6 mm2: 1 - traditional contact connection (without stabilizers), 2 - with a stabilizer - a conical washer made of shape-memory alloy, and 3 - with a stabilizer - a stack of alloyes made of shapememory alloy wire. The load current was set at 500 A. The initial compression force of the busbar contact connection was 12,000H. The change (reduction) in the compression force of the contact connection during the experiment was performed manually at 5-minute intervals with a step size of 2,000H.Table 3. Results of measurements of transient contact resistance R and temperature T of a contact connection with varying contact pressureMeasurement of transient resistance in a contact connection of aluminum busbars Applied Stabilizer - Stabilizer - force, Without conical alloy pack Test Time, s H stabilizer (state washer (SMA) of the art) (SMA)R, T, R, T, R, T, mOhm °C mOhm °C mOhm °C 1 0 12000 18 25 18 25 18 25 2 60 10000 21.06 2 21.06 2 21.06 2 3 12 10000 21.06 2 21.06 2 21.06 2 4 18 10000 21.06 2 21.06 2 21.06 2 5 24 10000 21.06 2 21.06 2 ' 21.06 2 6 30 8000 38.08 2 38.08 2 23.17 2 7 36 8000 38.08 3 37.77 2 21.28 2 8 42 8000 38.08 3 35.48 2 21.26 2 9 48 8000 38.08 4 35.44 2 21.19 2 10 54 6000 58.24 4 58.24 4 23.44 2 11 60 6000 58.24 4 49.67 3 23.24 2 12 66 6000 58.24 5 39.54 3 23.15 2 13 72 6000 58.24 5 38.12 2 23.08 3 14 78 6000 58.11 5 37.24 2 22.95 2 15 84 6000 58.02 5 37.19 2 22.78 2 16 90 4000 88.3.1 6 66.26 4 28.31 3 17 96 4000 91.01 6 54.31 4 26.23 3 18 1020 4000 91.27 6 47.06 3 25.35 3 19 1080 4000 89.11 6 43.21 3 24.37 3 20 1140 4000 88.10 6 39.34 3 23.11 321 1200 4000 87.93 6 39.21 3 23.03 3 22 1260 2000 115.1 7 91.11 7 32.11 3 23 1320 2000 122.1 8 83.31 6 28.31 3 24 1380 2000 125.2 8 68.42 5 26.11 3 25 1440 2000 127.1 9 55.18 4 25.27 3 26 1500 2000 128.1 9 46.23 3 24.17 3 27 1560 2000 126.1 9 46.21 3 24.01 3

[0103] Table 3 (together with the accompanying graphs shown in Figs. 17-18) presents data from 27 physical experiments measuring contact resistance and temperature across three design variants of aluminum busbar contact connections. As can be seen from Figs. 17-18, the use of an active stabilizer made of a copper-based SMA alloy in the third variant (3) significantly reduces the undesirable increase in contact resistance and connection temperature observed in variants (1) and (2), confirming its effectiveness.

[0104] In the second variant, where stabilizers with conical washers made of a shape-memory alloy are used, a sharp change in both the contact resistance and the connection temperature is observed, as shown in Figs. 17-18. This sharp shift is primarily due to the inertia of thermal processes, which leads to a slow response from the passive nature of the stabilizer. This method of contact pressure stabilization has a significant drawback: the occurrence of sharp changes in contact temperature worsens and accelerates the aging process of the contact connection.

[0105] In contrast, the data and graphs from the third embodiment show that the use of an active stabilizer consisting of a stack of SMA wire alloyes, according to this invention, significantly optimizes the process of stabilizing contact pressure and resistance. This prevents abrupt changes in connection temperature. Furthermore, the active stabilizer of this invention effectively slows down the aging process of detachable electrical contact connections, thereby optimizing their durability and reliability.

[0106] It should be emphasized that the embodiments described above are merely possible examples of implementation. Many variations and modifications ofthese embodiments are possible. All such changes and variations are intended to be included in this document within the scope of the disclosure and protected by the following claims. The invention has been described in detail with particular emphasis on certain preferred embodiments, but it will be understood that variations and modifications may be made within the spirit and scope of the invention.

Claims

CLAIMS1. A device made of a shape-memory alloy for improving electrical contact, comprising:at least two conductive contact elements with contact surfaces; at least one threaded connection, comprising a threaded element andat least one nut, designed to press the contact surfaces of said conductive elements together;at least one contact stabilizer located between said contact surfaces, wherein said stabilizer comprises a shape-memory alloy material configured to assume a shape selected from the group consisting of a mesh, a grid, or a porous metal material, wherein the area of said stabilizer corresponds to and is not less than the contact area of said contact surfaces.

2. The device of claim 1, wherein said active stabilizer is configured to regulate the contact pressure between said conductive contact surfaces during operation based on the thermodynamic properties of intermetallic compounds.

3. The device of claim 1, wherein the stabilizer is configured to maintain contact pressure at a nominal level in response to the accumulation of residual strain in the contact parts.

4. The device of claim 1, wherein the active stabilizer is configured to respond to direct heating by an electric current, providing localized regulation of contact pressure across the entire surface of the contact connection.

5. The device of claim 1, further comprising an electrically conductive lubricant comprising a combination of a semi-fluid lubricant and sharp burrs made of shapememory alloy powder, wherein said lubricant is applied to the contact surfaces to improve electrical conductivity and reduce oxide formation.

6. The device of claim 5, wherein the semi-liquid component of the grease penetrates the space between the contact surfaces, providing sealing against environmental contaminants, and wherein the powder contained in the grease fills the surface irregularities of the current-carrying contact parts.

7. The device according to claim 5, wherein the burrs of the shape-memory alloy powder are designed to allow the oxide film on the contact surfaces to be destroyed during thermal cycling of the contact connection.

8. The device of claim 5, wherein the stabilizer comprises one or more layers of grease and mesh stacked one on top of the other such that, upon heating, the stabilizer is activated locally at the micro-levels along the transverse direction of the contact connection, rather than across the entire surface between the contacts.

9. The device of claim 8, wherein said layers fill the gaps between the microlevels, providing electrical contact to maximize conductivity between the electrical contacts.

10. The device of claim 1, wherein the stabilizer is a package containing from 5 to 10 mesh units, each mesh unit being made of interwoven metal wires having a diameter of 0.1 mm or more.

11. A method for improving an electrical contact connection using a stabilizer, comprising the steps of:a - using, as the stabilizer, a copper-based shape-memory alloy wire having a diameter of 0.1 mm or more;b - using the stabilizer in the form of a mesh pack, each mesh made of a copperbased shape memory alloy wire;c - adapting the mesh pack to fill gaps equal to at least 25% of the thread pitch of the bolted connection.

12. The method according to claim 11, wherein the stabilizer additionally comprises an electrically conductive grease comprising a combination of a semi-fluid grease and sharp burrs made of a copper-based shape memory alloy powder, wherein said grease is applied to the contact surfaces to improve electrical conductivity and reduce oxide formation.

13. The method of claim 11, wherein the mesh stack undergoes deformation in the transverse direction, wherein the deformation is up to 25% of its initial transverse thickness.

14. The method of claim 11, wherein activation of the stabilizer prevents the entire contact connection from heating up completely, thereby preventing thetemperature from reaching levels close to the permissible limits, which contributes to extending the service life of the contact connection and improving efficiency.

15. The method of claim 11, further providing for monitoring and controlling the stabilizer’s reactive force in response to changes in electric current, thereby optimizing contact pressure for various electrical loads.

16. The method of claim 11, wherein the improvement of the electrical contact connection mitigates changes in contact resistance over time, ensuring stable and improved conductivity under various compression forces.

17. The method of claim 11, wherein direct heating of the stabilizer wires as the electric current increases leads to nearly simultaneous restoration of the stabilizer’s shape.

18. The method of claim 11, wherein direct electrical heating of the stabilizer leads to a sharp increase in reactive force, which, in turn, synchronously increases the contact pressure of the connection.

19. The method of claim 11, wherein a stabilizer made of a shape memory alloy wire is used in contact joints to respond to and automatically adjust changes in contact resistance time and temperature of said contact joints under various conditions.

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