EP4604140A1

EP4604140A1 - Cooling device for cooling of an electrical installation, electrical installation, method of cooling a component of an electrical installation, and use of a cooling device for cooling an electrical installation

Info

Publication number: EP4604140A1
Application number: EP24158397.0A
Authority: EP
Inventors: Oleksandr SOLOGUBENKO; Francoise MOLITOR
Original assignee: ABB Schweiz AG
Current assignee: ABB Schweiz AG
Priority date: 2024-02-19
Filing date: 2024-02-19
Publication date: 2025-08-20

Abstract

A cooling device configured for cooling an electrical installation having an electrical conductor carrying an alternating electric current. The cooling device includes a clamp and a beam being fixedly installed in the clamp. An unsupported end of the beam extends from the clamp and is configured for being provided at a distance from the conductor. The cooling device further includes at least one magnet fixedly provided about the beam. The at least one magnet is located adjacent an n-th node of flexural vibration of the beam, n being an integer equal or larger than 2. When a magnetic field generated by the alternating electric current interacts with the magnet, the magnet is configured for exerting an alternating torque onto the beam. The alternating torque causes the beam to oscillate in the n-th flexural mode.

Description

Aspects of the invention relate to the cooling of components in an electrical installation having an electrical conductor carrying an alternating electric current. In particular, the invention relates to providing a beam fixedly installed in a clamp, and causing the beam to oscillate.

Technical background:

Alternating electric currents in cables, busbars and transformer windings often generate heat which should be removed by an appropriate cooling system. The main thermal requirement for the cooling system is that, during a normal operation, the electric conductor temperature remains below a prescribed value, and the total temperature rise with respect to the ambient temperature remains below a prescribed value.
In some configurations, adequate cooling may be challenging. For example, cooling components within gas insulated enclosures, such as gas-insulated switchgear (GIS) compartments, is especially challenging, as GIS compartments are fully sealed. Mainly passive cooling elements such as heat sinks or gas coolers are used in medium voltage switchgear since long-term operation without maintenance or with little maintenance is often desirable. Passive cooling methods rely on heat transfer via natural convection of air and insulation gases, as well via thermal radiation, and may be insufficient in some configurations.
Forced convection cooling by means of fans or other powered mechanical devices is known, but may be unavailable or ineffective in some configurations due to spatial or other construction limitations, particularly for cooling components within enclosed compartments.
Some solutions propose air movers to promote local fluid acceleration, which rely on vibrating blades to enhance natural convective cooling. These solutions require a driving electronic circuit to vibrate the blade, and therefore may be prone to failure, and/or increase the cost and technical complexity of the system.
In light of the above, there is a need for improved systems and methods to provide cooling within an electrical installation. The devices, systems, methods and uses described herein solve the problem at least in part.

Summary of the invention

The invention is set out in the appended set of claims.
According to an aspect, a cooling device is described. The cooling device is configured for cooling an electrical installation having an electrical conductor carrying an alternating electric current. The cooling device includes a clamp and a beam being fixedly installed in the clamp. An unsupported end of the beam extends from the clamp and is configured for being provided at a distance from the conductor. The cooling device further includes at least one magnet fixedly provided about the beam. The at least one magnet is located adjacent an n-th node of flexural vibration of the beam, n being an integer equal or larger than 2. When a magnetic field generated by the alternating electric current interacts with the magnet, the magnet is configured for exerting an alternating torque onto the beam. The alternating torque causes the beam to oscillate in the n-th flexural mode.
According to an aspect, an electrical installation is described. The electrical installation includes an electrical conductor carrying an alternating electric current, and at least one cooling device according to aspects and/or embodiments described herein. The beam of the cooling device is provided at a distance from the conductor without contacting the conductor. The at least one magnet is arranged so that the magnetic moment of the magnet is at a non-zero angle with respect to a magnetic field generated by the alternating electric current.
According to an aspect, a method of cooling a component of an electrical installation is described. The method includes providing a cooling device at a distance from a conductor, the conductor carrying an alternating electric current. The cooling device includes a beam being fixedly installed in a clamp, an unsupported end of the beam extending from the clamp and having thereon provided at least one magnet. The at least one magnet is located at an n-th node of flexural vibration of the beam, n being an integer equal or larger than 2. The at least one magnet is arranged so that the magnetic moment of the magnet is at a non-zero angle with respect to a magnetic field generated by the alternating electric current. The method further includes causing the beam to oscillate in the n-th flexural mode. Causing the beam to oscillate includes causing an interaction between a magnetic field generated by the alternating electric current and the magnet, the interaction causing the magnet to exert an alternating torque onto the beam.
According to an aspect, the use of a cooling device according to aspects and/or embodiments described herein for cooling an electrical installation is described. The use may include performing a method according to aspects and/or embodiments described herein.
According to an aspect, a conductor is described. The conductor may be a busbar or a cable. The conductor may be configured for conveying a current e.g. between a first terminal and a second terminal. In some embodiments, the conductor may be a conductor of a component, such as a transformer, such as a cable forming a winding of a transformer. The conductor is configured for carrying an alternating electric current. When a current flows inside the conductor, the conductor generates a magnetic field, e.g. as described and/or approximated by Ampère's circuital law.
According to an aspect, an electrical installation is described. The electrical installation includes at least one conductor according to aspects and/or embodiments described herein. In some embodiments, the electrical installation is a medium voltage installation, such as medium voltage switch gear. Medium voltage, as understood herein, relates to a voltage of 40,5 Kilovolts (kV) or less, 35 kV or less, particularly 30 kV or less. Medium voltage may be understood as a voltage of 0.5 kV or more, or even 1 kV or more. The electrical installation may be utilized in power conversion, distribution, protection and/or switching. According to some embodiments, the electrical installation may be configured as gas-insulated switchgear (GIS), particularly a SF₆-free GIS. Likewise, the electrical installation may be an air-insulated switchgear installation, an installation of a motor control center, railway switchgear and/or traction power supply, and/or an installation for solar or wind power generation.
According to an aspect, a cooling device is described. The cooling device may be a passive cooling device. Passive may be understood as the cooling device not including, or being devoid of, a driving device for driving the cooling device, such as a dedicated driving circuit and/or an actuator for actuating a moving part of the cooling device powered by the dedicated driving circuit. The cooling device may be described as an air mover. The cooling device may be suitable for causing and/or assisting a convection of a gas, particularly boosting, amplifying and/or enhancing a convection of the gas. The cooling device may be devoid of piezoelectric elements and/or driving coils. The cooling device may be devoid of components consuming an electrical and/or pneumatic power.
According to an aspect, the cooling device includes a beam fixedly installed in a clamp. In particular, the beam may be cantilevered in the clamp and/or held, at one end of the beam, by the clamp, so that an unsupported end of the beam extends from the clamp.
According to an aspect, the beam may be configured to oscillate and/or vibrate in a manner commonly known and/or described as a cantilever beam subjected to free vibration. Accordingly, the beam may have natural frequencies, such as a first, second, third, fourth, fifth or even higher natural frequencies. Each of the natural frequencies may be considered a flexural mode of the beam.
The behavior of (oscillating) cantilevered beams is known in the art and may be described and/or modeled, at least in part, by the Euler-Bernoulli beam theory. For example, for a cantilever beam subjected to free vibration, and the system being considered as a continuous system in which the beam mass is considered as distributed along with the stiffness of the shaft, the equation of motion can be written as (L. Meirovitch, Analytical Methods in Vibrations, New York, NY: MacMillan, 1967): where E is the modulus of rigidity of beam material, I is the moment of inertia of the beam cross-section, Y(x) is displacement in y direction at distance x from fixed end, ω is the circular natural frequency, m is the mass per unit length, m = ρA(x), ρ is the material density, x is the distance measured from the fixed end.
According to an aspect, a magnet is described. The magnet may be a permanent magnet, such as a permanent ferro- or ferrimagnetic magnet. The magnet may be suitable for operating in an ambient temperature expected for the cooling application. For example, the magnet may have a sufficiently high Curie temperature, such as a Curie temperature of more than 400 °C, more than 500 °C, more than 600 °C, or even more than 700 °C. The working temperature of the magnet, which may be related to the Curie temperature, may be above the expected temperature within the cooling application. The magnet may have a coercivity suitably high to not be demagnetized by the alternating magnetic field generated near the conductor.
According to an aspect, a magnet is fixedly provided about the beam. More than one magnet may be provided. The magnet is provided adjacent a node of flexural vibration of the beam, such as at the node of flexural vibration. According to an aspect, the magnet is provided adjacent, at, and/or near the node of flexural vibration so that a torque being exerted onto the magnet is transferred to the beam near the node of flexural vibration. Accordingly, a torque, particularly a non-constant, periodic and/or an alternating torque, may cause the beam to oscillate at the frequency of the flexural mode corresponding to the node of the flexural mode, particularly if a frequency of the alternating torque and the frequency of the flexural mode of the beam are similar and/or identical to a natural frequency of the beam of the respective mode.
According to an aspect, a node of flexural vibration may be a position along a length L of the beam at which the beam remains at the essentially same position while vibrating and/or at which the beam shows no displacement with respect to a resting position during vibration. For example, in the first mode of flexural vibration, a node of flexural vibration may be defined by the position at which the beam is fixed in the clamp. Accordingly, in the first mode of flexural vibration, no first node of flexural vibration is present along the length L at a distance d from the clamping position. In a second mode of flexural vibration, the beam may have a (single) second node of flexural vibration along the length L at a distance d from the clamping position. In a third mode of flexural vibration, the beam may have two nodes of flexural vibration along the length L at a distance d from the clamping position. In a fourth mode of flexural vibration, the beam may have three nodes of flexural vibration along the length L at a distance d from the clamping position. In a fifth mode of flexural vibration, the beam may have four nodes of flexural vibration along the length L at a distance d from the clamping position. Even higher modes of flexible vibration having a higher number of nodes may be present and/or suitable.
According to an aspect, the beam may be a blade. For example, the blade may have a length L, a width and a thickness. In a projection, the blade may have an essentially rectangular shape, the shape being defined by the length and the width of the blade. Other shapes may be suitable, such as trapezoidal, triangular, elliptical, or other geometric shapes. Likewise, the beam may have a non-constant or inhomogeneous thickness. For calculating and/or modeling the behavior of complex beam shapes, the properties of the beam, such as the location of the nodes of flexural vibration and/or the natural frequencies of the beam, the above-referenced equation (1) may be modified. Likewise, the beam properties, such as the location of the flexural nodes, may be determined through experimentation, and/or may be simulated e.g. through finite element analysis according to methods known in the art.
According to an aspect, the beam may be flexible, particularly flexible to be elastically bent along the length L and/or about a surface normal of the surface defined by the length and width of the beam. According to embodiments, the beam may be a metallic beam, particularly a metallic blade. According to an aspect, the beam may be made from a steel, particularly a non-ferromagnetic stainless steel, such as a non-ferromagnetic austenitic stainless steel. Suitable steel alloys include, but are not limited to, grade SAE 304 and/or grade SAE 316(L). Additionally, or alternatively, the beam may be manufactured from polymer and/or composite materials. Beneficially, the beam being non-ferromagnetic may prevent the beam from interacting and/or interfering with magnetic fields, such as an alternating magnetic field generated by an alternating current carried by the electrical conductor.
Beneficially, a cooling device according to embodiments may provide the same or similar advantages as cooling devices utilizing vibrating blades while operating essentially passively, i.e. without requiring a driving device for driving an actuator to actuate the beam. Thus, the cooling device may be more flexibly installed in an electrical installation and/or less complex. Furthermore, the cooling device may provide more reliable cooling, since no failure-prone active devices are present.
Further advantages, features, aspects and details that can be combined with embodiments described herein are evident from the dependent claims, the description and the drawings.

Brief description of the Figures:

The details will be described in the following with reference to the figures, wherein

Fig. 1A: is a schematic perspective view of a cooling device according to embodiments;
Fig. 1B: is a schematic side view of a cooling device according to embodiments;
Fig. 2A: is a schematic side view of an oscillating cooling device according to embodiments at a first timepoint;
Fig. 2B: is a schematic side view of an oscillating cooling device according to embodiments at a second timepoint;
Fig. 3: shows configurations of a cooling device according to embodiments in an electrical installation according to embodiments; and
Fig. 4: shows a method of cooling a component of an electrical installation according to embodiments.

Detailed description of the Figures and of embodiments:

Reference will now be made in detail to the various embodiments, one or more examples of which are illustrated in each figure. Each example is provided by way of explanation and is not meant as a limitation. For example, features illustrated or described as part of one embodiment can be used on or in conjunction with any other embodiment to yield yet a further embodiment. It is intended that the present disclosure includes such modifications and variations.
Within the following description of the drawings, the same reference numbers refer to the same or to similar components. Generally, only the differences with respect to the individual embodiments are described. Unless specified otherwise, the description of a part or aspect in one embodiment applies to a corresponding part or aspect in another embodiment as well.
Fig. 1A and Fig. 1B (collectively Fig. 1) show a cooling device 100 according to embodiments being provided for cooling an electrical conductor 102. The electrical conductor 102 shown in Fig. 1 is depicted as a bus bar, however, other types of electrical conductors, such as cables, windings, rods or the like may be provided. The electrical conductor 102 may be a conductor within or of an electrical installation according to aspects and/or embodiments described herein.
The electrical conductor 102 carries an alternating current I_AC, flowing essentially perpendicular to the drawing plane of Fig. 1B. The electrical current carried by the conductor 102 generates an alternating magnetic field H_Ac schematically depicted in Fig. 1B by the field lines 104. The magnetic field H_AC alternates at the same frequency as the alternating current I_AC.
The cooling device 100 includes a clamp 110 and a beam 120 fixedly installed in the clamp 110. The clamp 110 may be affixed and/or mountable to a holding structure within an electrical installation, and may include a mounting surface (not shown) for mounting the clamp within an electrical installation. As shown in Fig. 1, the clamp 110 may be configured for clamping and/or chucking a portion of the beam 120 between two or more jaws. Likewise, the clamp 110 may include one or more brackets for fixedly supporting a portion of the beam so that the beam is fixedly installed in the clamp 110.
The beam 120 has an unsupported end extending from the clamp, i.e. an end of the beam opposite the end supported by the clamp 110. As shown in Fig. 1, the unsupported end is provided at a distance from the conductor 102, particularly without contacting the conductor 102. In the embodiment shown in Fig. 1, the unsupported end extends from the clamp 110 radially towards the conductor 102, however, other configurations, such as those shown in Fig. 3, are possible.
The cooling device 100 includes at least one magnet 130. In the embodiment shown in Fig. 1, two magnets 130 are shown, however, a single magnet, or more than two magnets may be provided. As shown in Fig. 1A, the magnets 130 are placed at a distance d from the clamping position, the distance d defining a position along the length L of the beam 120, both the distance d and the length L being measured from the clamping position, and the length L defining the length of the free portion of the beam 120.
The magnets 130 are located adjacent, near and/or at a node of flexural vibration equal or higher than 2, i.e. a node of the 2^nd, 3^rd, 4^th, ... mode of flexural vibration. In the embodiment shown in Fig. 1, the magnet 130 is located at the 2^nd node of flexural vibration, i.e. the node of the 2^nd mode of flexural vibration. As known in the art, for the 2^nd node of flexural vibration of a cantilevered beam, the position of the node is related to the length L as d = 0.783·L. As known in the art, for the 3^rd nodes of flexural vibration of a cantilevered beam, the position of a first 3^rd node is related to the length L as d = 0.5 ·L, and the position of a second 3^rd node is related to the length L as d = 0.868 ·L.
The magnets 130 are fixedly provided about the beam 120, e.g. fixed to the beam 120. In the embodiment shown in Fig. 1, the magnets 130 are affixed to a top surface of the beam 120. Likewise, additionally or alternatively, the magnets may be affixed to a bottom surface of the beam 120, or integrated into the beam 120, e.g. as inserts. The magnets 130 may be glued, attached with fasteners such as screws, clamped or otherwise fixedly provided about the beam 120.
In the embodiment shown in Fig. 1, the magnets 130 are permanent magnets provided as bar magnets. Alternatively to the embodiment shown in Fig. 1, a single bar magnet, e.g. spanning the width or a portion of the width of the beam 120, may be provided. Other types of magnets, such as plate magnets, rod magnets, cylindrical magnets or such may be provided.
As shown in Fig. 1B, the magnets 130 have a magnetization M defining a magnetic moment of the magnets 130 which, in the embodiment shown in Fig. 1, is essentially perpendicular to the magnetic field H_AC interacting with the magnets 130. For example, the N/S-poles of a bar magnet may be provided such that a first pole, such as the S-pole, points towards the end of the beam 120 provided in the clamp 110, and a second pole, such as the N-pole, points towards the open end of the beam 120.
Beneficially, the configuration shown in Fig. 1 may provide a strong interaction between the magnetization M of the magnets 130 and the magnetic field H_AC. It should, however, be noted that different orientations of the magnetization M with respect to the magnetic field H_AC are possible. In particular, adequate interaction between the magnets 130 and the magnetic field H_AC is obtainable for various angles in which the magnetic moment of the magnets 130 is at a non-zero angle with respect to a magnetic field H_AC.
Referring now to Fig. 2A and Fig. 2B (collectively Fig. 2), aspects of the operation of a cooling device according to embodiments is described. The cooling device may be the cooling device 100 described with reference to Fig. 1. The cooling device 100 may be provided in an electrical installation according to embodiments.
In Fig. 1, the cooling device 100 is shown in a resting position, while in Fig. 2, the cooling device 100 is oscillating. As shown in Fig. 2, according to embodiments, the oscillation causes the beam 120 to vibrate so that portions of the beam 120 distant from nodes of flexural vibration and/or the clamping position are deflected from the neutral position indicated in Fig. 2 by the dotted line.
In Fig. 2, the beam 120 is shown to vibrates in a 2^nd mode of flexural vibration. Accordingly, a 2^nd node of flexural vibration is present and/or observable. The magnet 130 is provided adjacent, near or at the 2^nd node of flexural vibration, and has little or no displacement from the neutral position.
The oscillation is caused by an interaction between the magnet 130 and the magnetic field H_AC generated by an alternating current, such as the current I_AC flowing inside the conductor 102 shown in Fig. 1. The magnetic interaction causes forces to be exerted onto the magnet, the forces including a torque being exerted onto the magnet fixedly provided about the beam. Other forces, such as linear forces, may be present, however, linear forces may be counteracted by the beam 120. Accordingly, the main driving force causing the beam 120 to oscillate may be the alternating torque being applied onto the beam 120, by the magnet 130, at or near a node of flexural vibration.
At the first timepoint t₁ shown in Fig. 2A, at an antinode of the beam 120 located in-between the clamp and the 2^nd node of flexural vibration, the beam 120 is bent upwards and the open end of the beam 120 is bent downwards. At the second timepoint t₂ shown in Fig. 2B, at an antinode of the beam 120 located in-between the clamp and the 2^nd node of flexural vibration, the beam 120 is bent downwards and the open end of the beam 120 is bent upwards. As shown in Fig. 2, the orientation of the alternating magnetic fields H_AC is reversed between timepoint t₁ and t₂, while the magnetization and/or magnetic momentum of the magnet 130 remains the same. Accordingly, a torque exerted onto the magnet through the magnetic interaction between the magnetic momentum of the magnet 130 and the magnetic field H_AC alternates with the frequency of the current I_AC and is transferred from the magnet 130 onto the beam 120. It should be noted that a phase-shift may be present between the time-point of maximum displacement of an antinode of the beam 120 and the maximum amplitude of the magnetic field H_AC.
According to embodiments, the oscillation may include a resonance of the beam 120. Resonance may occur in case the natural frequency of the mode corresponding to the node of flexural vibration adjacent to which the magnet 130 is placed is similar or identical to the frequency of the alternating current I_AC and/or the alternating magnetic field H_AC. Beneficially, a resonating cooling device 100 may show a strong oscillation even when excited by a comparatively weak magnetic field H_AC. Accordingly, a natural frequency of the flexural mode of the beam may correspond to the frequency of the alternating electric current. For example, the beam 120 may be chosen and/or tuned to have a natural frequency of within ± 5 Hz, ± 3 Hz, ± 2 Hz, or even within ± 1 Hz of the alternating current in the desired mode of flexural vibration, such as the 2^nd, 3^rd, 4^th, 5^th or even higher mode. Typical frequencies of the alternating current include 50 Hz or 60 Hz, however, the cooling device 100 may be adapted and or tuned to yet further frequencies. Tuning the beam 120 may include changing geometric properties of the beam 120, such as a length and/or shape of the beam 120, and/or selecting a material or material composition of the beam having a desired modulus of rigidity E. For example, the second natural frequency of a cantilevered beam may be calculated and/or approximated according to the following equation (Gibson, R.F., Principles of composite material mechanics. 4th ed2016: CRC Press. 1-657): $f_{2} = \frac{{(4.694)}^{2}}{2 {πL}^{2}} \sqrt{\frac{EJ}{ρA}}$ where J is the area moment of inertia of the cross section about the centroidal axis of the beam, A is the cross-sectional area of the beam, ρ is the density, and E is the modulus of elasticity of the beam.
Beneficially, the cooling device may be positioned near a conductor that requires cooling, and be driven by the magnetic field emitted from the conductor, without requiring a separate actuator and/or driving device. The vibration of the beam may disturb and/or propel the air or other fluid surrounding the beam and/or cause an increased convection of air or other gases near the beam, which may beneficially assist natural convection. Beneficially, an amplitude of the beam oscillation may be proportional to the current being conveyed within the conductor, thus providing increased cooling for conductors expected to produce increased heat, without requiring additional regulators. Beneficially, by oscillating the beam in a mode of flexural vibration higher than the first mode, adequately long beams may be provided that offer the desired air moving capability, while oscillating at a natural frequency of the higher mode corresponding to a frequency of the alternating current carried by the conductor.
Referring now to Fig. 3, the cooling device 100 described with reference to Fig. 1 and/or Fig. 2 is shown in alternative exemplary configurations 300, 302 within an electrical installation. It should be noted that these configurations are not to be understood as limiting, and instead serve as examples for multiple possible configurations of the cooling device according to embodiments in an electrical installation. In a first configuration, the cooling device 100 may be provided essentially as shown in Fig. 1. For example, as shown in Fig. 1, the beam 120 may extend from the clamp 110 essentially radially towards the conductor 102.
Likewise, e.g. as shown in configuration 300 or configuration 302, the beam 120 may be provided at an angle relative to a radial direction of the conductor 102. For example, in the configuration 300, the beam extends essentially parallel to a surface of the conductor 102, while in the configuration 302, the beam extends towards the conductor at an angle of about 45° relative to a radial direction of the conductor 102.
In some configurations according to embodiments, such as the configuration 300 shown in Fig. 3, the magnetization of the magnet 130 may be oriented differently than explained for the cooling device 100 shown in Fig. 1. The skilled person understands that the torque described herein is not generated in case the magnetic moment of the magnet 130 is parallel, i.e. at a zero angle, with respect to the magnetic field H_AC generated by the conductor 102. For example, in the configuration 300, to provide the magnetic moment of the magnet 130 at a non-zero angle with respect to a magnetic field generated by the alternating electric current, the N/S-poles of the magnet 130 may be rotated by an angle of about 20° to about 90° relative to the configuration shown in Fig. 1, e.g. by rotating the bar magnet 130 about its axis. For example, in configuration 300, an N-pole of the magnet 130 may point towards a top surface of the beam 120, the surface being defined by the plane formed between the length and width of the beam 120, and an S-pole of the magnet 130 may point away from the surface of the beam 120.
In the exemplary configuration 302, both the magnetization M of the magnet(s) 130 described with reference to Fig.1, as well as the magnetization of the magnet 130 described with reference to configuration 300 shown in Fig. 3 are provided at a non-zero angle with respect to the magnetic field H_AC. Accordingly, a torque suitable for causing an oscillation of the beam 120 is generated in either orientation.
According to embodiments, while embodiments described herein may show providing the magnet 130 at the 2^nd flexural node, other flexural nodes may be chosen. For example, one or more magnets 130 may be provided at one or more of the 3^rd flexural node, one or more of the 4^th flexural node, and/or one of the 5^th flexural node, or even a higher than 5^th flexural node. Accordingly, oscillating the beam 120 may include causing the beam to oscillate at a natural frequency of a flexural mode higher than 2, between 2 and 5, between 2 and 4, or between 2 and 3. Choosing the mode may include providing the one or more magnet 130 at a distance d along the length L of the beam 120 corresponding to the desired node. Oscillating the beam 120 in modes having more than one node along the length L, such a the 3^rd and higher mode, may include providing one or more magnets at a single node, or multiple nodes, such as all nodes. In embodiments where magnets are provided at more than one node, the orientation of the magnetic moment of the magnets may alternate between each node so that the torques applied to different nodes do not cancel out.
According to embodiments, e.g. as shown in Fig. 1, Fig. 2 and Fig. 3, the magnet may be provided near a flexural node, such as adjacent a flexural node. For example, a magnet may be provided on a surface of the beam 120, while the flexural node is located within a body of the beam. For example, in a beam having a length L, the node of flexural vibration may be located a distance d from an end of the beam fixedly installed in the clamp, and the magnet may be located along the length L so that a rotational axis of the torque exerted by the magnet is offset from the node of flexural vibration along the length L, and optionally along the direction of the thickness of the beam, by 0. 1 ·L or less, 0.05 ·L or less, 0.02 ·L or less, or even by 0.01 ·L or less. Beneficially, due to transferring a torque instead of a linear force, even an inaccurate placement of the magnet 130 along the beam 120 within the above-stated limits may cause the desired oscillation.
According to embodiments, a mass may be provided at the node of flexural vibration. The mass may include a mass of the magnet 130, or an additional mass, e.g. of a weight. The mass may cause the beam to further oscillate at a lower mode than that of the node of flexural vibration. For example, when providing the mass at the 2^nd node of flexural vibration, an oscillation in the 1^st mode of vibration may be induced in addition to the oscillation in the 2^nd mode of vibration. Beneficially, the additional oscillation in the lower mode of vibration may additionally increase an airflow caused by the cooling device.
According to embodiments, an electrical installation is described. The electrical installation includes at least one conductor, such as the conductor 102 shown in Fig. 1 and Fig. 3. The conductor 102, during operation of the electrical installation, is configured for carrying an alternating current I_AC. The electrical installation includes at least one cooling device according to embodiments described herein, such as the cooling device 100 shown in Fig. 1, Fig. 2 and Fig. 3. The cooling device 100, particularly a beam 120 of the cooling device 100, is provided at a distance from the conductor 102 without contacting the conductor. The cooling device 100 includes a magnet 130, the magnet 130 being provided at a distance from the conductor 102 so that an alternating magnetic field H_AC generated by a current flowing within the conductor 102 interacts with the magnetization M and/or the magnetic moment of the magnet 130, particularly to generate a torque suitable for causing the beam 120 to oscillate. The magnet 130 of the cooling device is arranged so that the magnetic moment of the magnet 130 is at a non-zero angle with respect to the magnetic field H_AC.
According to embodiments, the electrical installation may include a closed compartment, the compartment enclosing the conductor or portions of the conductor. For example, the electrical installation may be a gas-insulated switchgear compartment having a gas-insulated enclosure. An insulating gas, such as SF₆ or, beneficially, an insulating gas other than SF₆, such as dry air or other gases, may be provided within the enclosure. Beneficially, a cooling device described herein may be particularly suitable for SF₆-free electrical installations, since a cooling device according to embodiments may mitigate a reduced cooling efficiency and/or passive convective heat transfer capability of a non-SF₆ gas.
In particular, according to embodiments, the cooling device is configured for increasing, through an oscillation of the beam, a gas convection within the electrical system. For example, a natural, passive convection of gases within the electrical installation, such as a thermal convection, may be increased by arranging one or more cooling devices so that a resultant air flow caused by the cooling device has the same or similar direction as the natural convection.
According to embodiments, the cooling device 100 may be arranged near a conductor as shown in Fig. 1 or Fig. 3 to direct a resultant air flow towards, past and/or along a conductor. Additionally, or alternatively, one or more cooling device 100 may be arranged to direct an airflow towards further components of the electrical installation, such as heatsinks or other components not carrying the current I_AC, or even to increase an overall gas circulation e.g. inside an enclosure.
According to embodiments, a cooling device 100 may be provided within the electrical installation at a controlled potential. For example, one or more structures of the cooling device 100, such as the clamp 110, the beam 120, and/or the magnet 130 may be made from a conductive material, such as a metal. Particularly in high electric field environments, such as medium or even high voltage switchgear, it may be desirable to control the potential of the cooling device 100. Accordingly, an electrical installation according to embodiments may include an electrical connection between the cooling and/or conductive structures of the cooling devices, and a controlled potential, such as a ground potential, or the potential of the conductor the cooling device 100 is placed nearby.
According to embodiments, a plurality of cooling devices 100 may be provided in the same installation. Beneficially, the cooling device does not require additional driving circuits and/or wiring, and may thus be easily and flexibly installed. Accordingly, additional cooling devices may be added where desired, without requiring an extensive adaptation of the electrical installation. Beneficially, the plurality of cooling devices 100 may be provided by cooling devices having various shapes and/or sizes, adapted e.g. according to spatial and or cooling performance requirement. For example, differently sized cooling devices may be provided in the same installation, where larger cooling device operate in a higher mode of flexural vibration, such a 3^rd mode of flexural vibration, and smaller cooling devices operate in a lower mode of flexural vibration, such as a 2^nd mode of flexural vibration.
While particular benefits of the disclosure have been described with reference to gas-insulated switchgear, the cooling device according to embodiments may be provided in yet further applications, and offer similar benefits in other types of electrical installations.
Referring now to Fig. 4, a method 400 of cooling a component of an electrical installation is described. The electrical installation may be an electrical installation according to embodiment described herein. The cooling device may be a cooling device according to embodiments described herein, such as the cooling device 100 described with reference to Fig. 1, Fig. 2 and/or Fig. 3.
The method includes providing 410 a cooling device at a distance from a conductor, the conductor carrying an alternating electric current. The cooling device includes a beam being fixedly installed in a clamp, an unsupported end of the beam extending from the clamp and having thereon provided at least one magnet. The at least one magnet is located at an 2^nd or higher node of flexural vibration of the beam. The at least one magnet is arranged so that the magnetic moment of the magnet is at a non-zero angle with respect to a magnetic field generated by the alternating electric current.
The method 400 further includes causing 420 the beam to oscillate in the 2^nd or higher mode of flexural vibration. Causing the beam to oscillate may include conveying an alternating current through the conductor, and/or generating a magnetic field around the conductor by the alternating current. The magnetic field interacts with the magnet. An interaction between the magnetic field and the magnet causes the magnet to exert an alternating torque onto the beam. The alternating torque may periodically cause a flexion of the beam near the flexural node, which may transfer energy to the beam suitable for causing and/or maintaining the oscillation of the beam.
According to embodiments, the alternating current may have a frequency f corresponding e.g. to a grid frequency. Accordingly, the method 400 may include providing the alternating current at the frequency f. For example, the frequency f may be 50 Hz or 60 Hz, however, other frequencies may be equally suitable. A natural frequency of the beam of the mode of flexural vibration corresponding to the node of flexural vibration at which the magnet is provided may correspond to the frequency f. Accordingly, the beam may resonate in the mode of flexural vibration at the frequency of the AC current.
According to embodiment, the method 400 may include maintaining the cooling device at a controlled electrical potential. For example, the method may include maintaining the cooling device at a ground potential, or at the electrical potential of the conductor. Accordingly, the method may include forming an electrical connection between conductive portions of the cooling device, such as the clamp, the beam and/or the magnet, between the potential. In some embodiments, the controlled electrical potential may be obtained by mounting the cooling device to a component of an electrical installation having the desired controlled potential, the electrical connection being formed by the mounting and/or the mounting means.
While the foregoing is directed to some embodiments, other and further embodiments may be devised without departing from the basic scope, and the scope is determined by the claims that follow.

Claims

Cooling device (100) for cooling an electrical installation comprising an electrical conductor (102) carrying an alternating electric current (I_AC), comprising:
a clamp (110);

a beam (120) being fixedly installed in the clamp (110), an unsupported end of the beam (120) extending from the clamp (110) and being configured for being provided at a distance from the conductor (102); and

at least one magnet (130) being fixedly provided about the beam (120), wherein

the at least one magnet (130) is located adjacent an n-th node of flexural vibration of the beam (120), n being an integer equal or larger than 2, and wherein

when a magnetic field (H_AC) generated by the alternating electric current (I_AC) interacts with the magnet (130), the magnet (130) is configured for exerting an alternating torque onto the beam (120), the alternating torque causing the beam (120) to oscillate in an n-th flexural mode.
The cooling device (100) according to claim 1, wherein the beam (120) is cantilevered in the clamp (110).
The cooling device (100) according to claim 1 or 2, wherein a natural frequency of the n-th flexural mode of the beam (120) corresponds to a frequency of the alternating electric current (I_AC).
The cooling device (100) according to any one of the preceding claims, wherein n is an integer between 2 and 5.
The cooling device (100) according to any one of the preceding claims, wherein the beam (120) has a length L;
the n-th node of flexural vibration of the beam (120) is located at a distance d from an end of the beam (120) fixedly installed in the clamp (110); and

the magnet (130) is located along the length L so that a rotational axis of the torque exerted by the magnet (130) is offset from the n-th node of flexural vibration along the length L by 0.01 ·L or less.
The cooling device (100) according to any one of the preceding claims, wherein the beam (120) is a metallic beam (120), particularly a beam (120) made from non-ferromagnetic austenitic stainless steel.
The cooling device (100) according to any one of the preceding claims, comprising a mass provided at the n-th node of flexural vibration of the beam (120), the mass causing the beam (120) to further oscillate in an m-th flexural mode, wherein m is an integer between 1 and less than n.
An electrical installation, comprising:
an electrical conductor (102) carrying an alternating electric current (I_AC), and

at least one cooling device (100) according to any one of claims 1 to 7; the beam (120) of the cooling device being provided at a distance from the conductor (102) without contacting the conductor (102), wherein

the at least one magnet (130) is arranged so that a magnetic moment of the magnet (130) is at a non-zero angle with respect to a magnetic field (H_AC) generated by the alternating electric current (I_AC).
The electrical installation according to claim 8, wherein the electrical conductor (102) comprises a busbar or a cable, preferably provided within a gas-insulated enclosure of the electrical installation.
The electrical installation according to claim 8 or 9, wherein the electrical installation is a gas-insulated switchgear compartment.
The electrical installation according to any one of claims 8 to 10, wherein the cooling device is configured for increasing, through an oscillation of the beam (120), a gas convection within the electrical installation.
A method (400) of cooling a component of an electrical installation, comprising:
providing (410) a cooling device at a distance from a conductor (102), the conductor (102) carrying an alternating electric current (I_AC), the cooling device comprising:
a beam (120) being fixedly installed in a clamp (110), an unsupported end of the beam (120) extending from the clamp (110) and having thereon provided at least one magnet (130), wherein

the at least one magnet (130) is located at an n-th node of flexural vibration of the beam (120), n being an integer equal or larger than 2, and wherein

the at least one magnet (130) is arranged so that a magnetic moment of the magnet (130) is at a non-zero angle with respect to a magnetic field (H_AC) generated by the alternating electric current (I_AC); the method further comprising:

causing (420) the beam (120) to oscillate in the n-th flexural mode, comprising:
causing an interaction between a magnetic field (H_AC) generated by the alternating electric current (I_AC) and the magnet (130), the interaction causing the magnet (130) to exert an alternating torque onto the beam (120).
The method according to claim 12, wherein the alternating electric current (I_AC) has a frequency f of 50 Hz or 60 Hz, and wherein a natural frequency of the n-th flexural mode of the beam (120) is equal to the frequency f.
The method according to any one of claims 12 or 13, comprising:
maintaining the cooling device (100) at a controlled electrical potential.
Use of the cooling device (100) according to any one of claims 1 to 7 for cooling an electrical installation, the use preferably comprising the method (400) according to any one of claims 12 to 14.