RU196997U1 - COOLING COOLER COOLING UNIT - Google Patents

Abstract

The utility model relates to cryogenic and electrical insulating technology. The technical result of the utility model is to provide electrical insulation of the coil from a high-temperature superconducting wire (HTSC) while ensuring high thermal conductivity from the metal elements of the biscuit solenoid. To achieve a technical result, a cooling device for a biscuit solenoid consisting of a disk and a ring, a high-temperature superconducting coil with a copper coating and a fixing layer “Apezon N” deposited on its side surface is proposed, an uninsulated tape superconducting wire is used as a winding material, and as heat-conducting discs and rings uses a hybrid material in the form of an array of aluminum coated with an electrically insulating layer of aluminum oxide. 2 ill.

Description

Technical field

The utility model relates to a cryogenic and electrical insulating technique and can be used to cool the windings of a superconducting electromagnet of the solenoid type made of a series of flat windings (biscuits) of tape high-temperature superconductors.

State of the art

Today, one of the most promising types of superconducting solenoids based on high-temperature superconductors (HTSC) for creating strong magnetic fields are considered to be biscuit (disk) type solenoids, since they have high repair ability (by replacing biscuits) and correspond to the form factor of wires (thin tape superconducting wires , a typical thickness of 0.1-0.2 mm and a width of 4-12 mm). Flat windings (biscuits) are made of ribbon wire, in which the outer coating is made of copper (the thickness of the copper coating is 0.02-0.03 mm). To improve thermomagnetic stability, superconducting tapes are not coated with an insulating material, which improves the cooling conditions of the winding to cryogenic temperatures using indirect cooling (cooling by a cryorefrigerator due to heat transfer through the materials of the solenoid). In the operating mode, the current in the solenoid winding flows through the superconducting layer of the wire and the absence of electrical insulation of adjacent turns in the biscuit does not affect the magnetic field created by the solenoid. However, adjacent winding windings must be electrically isolated to reduce the time it takes for the current to enter the solenoid. Thus, with indirect cooling of electrical devices, the heat-removing elements must simultaneously have a high coefficient of thermal conductivity and provide electrical insulation.

In existing designs (prototypes), these requirements are met through the use of copper heat-conducting elements and thin dielectric films (polytetrafluoroethylene, polyimide, etc.)

A known method of cooling a superconducting coil and fixing adjacent plates (patent JP 6355914), where a film of polytetrafluoroethylene (PTFE) is used as an insulating material between HTSC tapes, impregnate the end surfaces of a superconducting coil wound together with a PTFE film, side plates and a superconducting coil wound together with a PTFE film is attached to each other. However, this method of electrical insulation helps to reduce the ergonomics of the design of the solenoid, since for the necessary fixation of the film, which is about 50-100 microns, an additional layer of epoxy is used.

The solution described in the article (T. Takematsu et al., Physica C, Vol. 470, p. 674-677) is known in which an epoxy resin is used to insulate the heat-conducting material between the high-temperature superconducting coil and the metal part of the biscuit. However, according to the data presented in the article, epoxy resin degrades the critical current of the HTSC coil due to strong mechanical stresses caused by the difference in the thermal expansion coefficients of the materials used.

The closest in technical essence to the claimed utility model is a method of manufacturing a high-temperature superconducting coil (Application for invention JP 2018011078), in which HTSC wires are insulated from each other by a tape-like polytetrafluoroethylene (PTFE) film, the end surfaces of the HTSC coil are impregnated with epoxy resin and, thus are fixed to the cooling plates.

The disadvantage of this method is that the epoxy layer is deformed, as well as the low thermal conductivity of PTFE films and epoxy (0.25 W / (m * K) and 0.59 W / (m * K), respectively), which worsens temperature regime of the solenoid.

Utility Model Disclosure

The technical problem to be solved by the claimed utility model is the provision of electrical insulation of the solenoid windings without increasing the thickness of the biscuit solenoid structure and with high heat transfer efficiency.

The technical result of the claimed utility model is the use of hybrid aluminum elements coated with a thin layer of aluminum oxide (Al ₂ O ₃ ), made by the anodization method, the wire of the high-temperature superconducting coil is not insulated.

The technical result of the claimed utility model is achieved by the fact that in the proposed cooling device of a biscuit solenoid consisting of a disk and a ring, a high-temperature superconducting coil with a copper coating, with an Apezon N fixing layer deposited on its side surface, an uninsulated tape superconducting wire is used as a winding material, and in As the heat-conducting disks and rings, a hybrid material is used in the form of an array of aluminum coated with an electrically insulating layer of aluminum oxide.

The combination of the above essential features leads to the fact that:

- the electrical insulating layer is created by oxidizing the surface of the aluminum disk and does not lead to an increase in the total thickness of the biscuit solenoid design, while high heat transfer efficiency is achieved due to the high thermal conductivity of both the disk material (aluminum) and the electric insulation coating material (Al ₂ O ₃ ).

- the claimed solution in conditions of cryogenic temperatures has high electrical stability and mechanical strength, after repeated thermocyclic tests under operating pressure, simulated in the conditions of operation of a balet solenoid.

Brief Description of the Drawings

In FIG. 1-2 shows a diagram of a device for cooling a biscuit solenoid, where the numbers indicate:

1 - a disk of a biscuit solenoid;

2 - a ring of biscuit solenoid;

3 - high temperature superconducting coil;

4 - an insulating layer of Al ₂ O ₃ ;

5 - fixing layer Apezon N.

Utility Model Implementation

The solenoid biscuit cooling device of FIG. 1-2 consists of disks 1 and rings 2 made of industrial aluminum, coated with a layer of aluminum oxide 4. A coil 3 of an uninsulated tape superconducting wire for thermomagnetic stability is wound on ring 2. The end surface of the superconducting coil 3 is coated with a thin layer of heat-conducting grease 5 (Apezon N) with a thickness of 10-15 microns to improve adhesion to the surface and thermal contact.

The heat-conducting electrical insulating layer of aluminum oxide 4 on the surfaces of the disk 1 and ring 2 was obtained by anodizing in a sulfate medium, the coating thickness is 15-18 microns. The breakdown voltage of the layer depends on the thickness of the coating. At the specified thickness, the breakdown voltage is 400-500 V, which is sufficient for the safe operation of the biscuit-type solenoid under any operating conditions.

An uninsulated tape superconducting wire with a copper coating is used, and a hybrid material in the form of an aluminum array coated with a thin 15-18 μm electrically insulating layer of aluminum oxide is used as heat-conducting disks and rings.

The proposed device under conditions of cryogenic temperatures has high electrical stability and mechanical strength, after repeated thermocyclic tests under operating pressure, simulated in the conditions of operation of a balet solenoid.

The biscuit disk 1 (carrying out heat transfer) is the main element of indirect cooling of the superconducting winding 3 (when working in vacuum when using a cryorefrigerator to cool the solenoid). It has a maximum thermal conductivity in the temperature range of 40-70 K, and allows you to create a non-conductive anodized coating 4, which protects the layers of neighboring biscuits from electrical short circuit. The thermal conductivity of the anodized coating is 25-30 W / m * K, which is ten times higher than the thermal conductivity of other electrical insulating materials. With repeated thermal cycling of biscuits, the properties of the electrical insulating coating do not change.

When anodizing the surface of the aluminum disk 1 and ring 2, sulfuric acid H ₂ SO ₄ 200 g / l, current density 2.5 A / dm ² , the process time is 37 minutes, the electrolyte temperature was T = 14-16 ° C is used as the electrolyte The electric mode is anode.

During operation of the inventive device, heat is removed from the superconducting coil 3 through an insulating layer of Al ₂ O ₃ 4 to disk 1 and then to a copper cold pipe to the cryorefrigerator (not shown in Fig. 1-2). Layer 4 provides electrical insulation while maintaining high thermal conductivity between the side surface of the winding 3 and the disk 1.

Claims (1)

The device for cooling a biscuit solenoid winding, consisting of a disk and a biscuit solenoid ring, a high-temperature superconducting coil with a copper coating and a fixing layer “Apezon N” applied to its side surface, characterized in that an uninsulated tape superconducting wire is used as a winding material, and as heat-conducting discs and rings uses a hybrid material in the form of an array of aluminum coated with an insulating layer of aluminum oxide.

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