CN110111969A - A kind of insulation reinforcement means of superconducting coil - Google Patents

Abstract

The invention discloses an insulation reinforcement method for a superconducting coil, in particular to a reinforcement and insulation method for a superconducting coil with high mechanical properties, high thermal stability, high electrical insulation performance and no critical current attenuation. During the water cooling process, the water around the coil gradually solidifies into ice, completing the insulation and reinforcement of the superconducting coil. Compared with the existing insulation strengthening method, the invention uses a simple and economical method to make the superconducting coil have better mechanical properties, thermal stability and electrical insulation performance, and at the same time, it will not cause the attenuation of the critical current of the superconducting wire. The method has the advantages of simple manufacturing process, low cost and no pollution to the environment; the superconducting wire in the ice-reinforced magnet can be reused; when the insulation is damaged, the reinforced structure of the coil can be repaired again. The method is simple to operate, and is a very effective and excellent method for strengthening the insulation of a superconducting coil.

Description

A method for strengthening the insulation of a superconducting coil

technical field

The invention relates to the field of magnet design and processing, and more specifically, to an insulation strengthening method for a superconducting coil.

Background technique

Superconductors have extremely low resistivity at low temperatures, and there is almost no power loss. With the development of superconducting tape manufacturing technology, magnets wound with superconducting tapes have been widely used in nuclear magnetic resonance, accelerators and other fields. In high-field superconducting magnets, the ribbon will be subjected to huge Lorentz force, so reinforcement is very important for high-field superconducting magnets, and suitable reinforcement materials should be able to maintain the mechanical structure of superconducting magnets under high fields stability, but also should have good thermal conductivity and electrical insulation. In order to facilitate large-scale application, reinforcement materials should also have the advantages of simple processing technology, low cost, and no environmental hazards.

The traditional superconducting magnet reinforcement method mostly adopts the reinforcement method of epoxy resin impregnation, but there are some problems in this reinforcement method:

(1) The shrinkage rate of the commonly used epoxy resin at low temperature is 4 to 5 times higher than that of most metal materials. During the cooling process of the magnet, due to the large difference in shrinkage rate, the epoxy resin will have a greater impact on the surface of the strip. transverse tensile stress. This phenomenon is more destructive to the second-generation high-temperature superconducting tape with a multilayer structure. When the tensile stress exceeds the stress limit that the tape can withstand, the tape will produce delamination, which will eventually lead to the critical current of the magnet. attenuation;

(2) The thermal conductivity of epoxy resin at low temperature is low. When local overheating occurs in the magnet, the heat cannot be transferred out in time, causing local heat accumulation, and may burn the magnet in severe cases;

(3) The process of reinforcing the magnet with epoxy resin is complex and costly, and the strips in the magnet reinforced with epoxy resin cannot be reused, which has certain limitations in application;

(4) Epoxy resin is difficult to degrade in the natural state, which will cause pollution to the environment.

At present, other commonly used reinforcement methods for superconducting magnets also have their own limitations. For example, the mechanical strength of the paraffin reinforcement method is low, and the stability of the mechanical properties of the magnet cannot be maintained under high field; the production process of the heat shrinkable tube reinforcement method is complicated. for large-scale applications. The above are the outstanding problems in the insulation and reinforcement of superconducting coils at present, which seriously affect the application of superconducting coils under high field.

Contents of the invention

Aiming at the defects of the prior art, the purpose of the present invention is to solve the problem that the method of using epoxy resin to insulate and reinforce the superconducting coil in the prior art will lead to attenuation of the critical current of the magnet, local heat accumulation, complicated process and pollution to the environment, and Other reinforcement methods also have limitations and other technical problems.

In order to achieve the above object, the present invention provides a method for strengthening the insulation of a superconducting coil, comprising the following steps:

Pour water into the container where the superconducting coil is located until the superconducting coil is completely submerged in water;

The water is cooled until the water is completely condensed into ice, and the ice is used to reinforce the superconducting coil, and the stress generated by ice shrinkage on the superconducting strip during the cooling process does not exceed the stress that the superconducting strip can withstand limit, so that ice does not cause the critical current decay of the superconducting coil, the superconducting tape is used to wind the superconducting coil, and the superconducting coil works under low temperature conditions.

Optionally, the cooling rate needs to be lower than a preset threshold, so as to avoid cracks generated during cooling and icing, which will affect the mechanical properties of the ice.

Optionally, the water is deaerated water.

Optionally, the method also includes the steps of:

Before cooling the water, let the water fully soak the superconducting coils, and let the water fill the gaps between the superconducting strips.

Optionally, air bubbles are avoided during the cooling and freezing process of the water.

Optionally, the method also includes the steps of:

If the water produces bubbles or cracks in the ice during cooling, return the ice-reinforced superconducting coil to normal temperature;

Expelling the gas in the water, or pouring out the water in the container where the superconducting coil was originally located, and re-adding degassed water into the container until the superconducting coil is completely submerged in water;

The water is cooled to freeze until the water is completely condensed into ice.

Generally speaking, compared with the prior art, the above technical solution conceived by the present invention has the following beneficial effects:

The method for strengthening the insulation of superconducting coils provided by the present invention uses ice to reinforce the superconducting coils. The shrinkage rate of ice at low temperatures is close to that of superconducting strips, and the tensile stress on the strips caused by ice shrinkage during cooling is very small. There is no critical current decay phenomenon of superconducting coils after multiple thermal cycles; the thermal conductivity and specific heat capacity of ice are higher than those of epoxy, and when local overheating occurs inside the magnet, ice can absorb it without causing a large temperature rise heat, and conduct the heat out in time to avoid heat accumulation and prevent permanent damage to the magnet; the conductivity of ice is very low, and the superconducting ice coil has good electrical insulation properties; the mechanical strength of ice is high, and it can be used under high field It has a good reinforcement effect on the magnet.

In the insulation strengthening method of the superconducting coil provided by the present invention, if the ice used for strengthening the magnet is damaged by cracks or the like, the magnet can be returned to room temperature first, and then cooled to freeze, and the reinforcement of the coil can be completed again; the manufacturing process of ice reinforcement is simple and low cost. Low cost, greater practicability; ice-reinforced superconducting wires can be recycled, saving costs; ice has no pollution, and is an environmentally friendly reinforcement material.

The present invention proposes a way of using ice as a reinforcing material for a superconducting magnet. The water filled around the magnet condenses into ice during the simultaneous cooling process with the magnet, thereby reinforcing and insulating the magnet. This reinforcement method can effectively solve the problems existing in the traditional magnet reinforcement method.

Description of drawings

Fig. 1 is the flow chart of the insulation strengthening method of the superconducting coil provided by the present invention;

Fig. 2 is the structural diagram of the ice-reinforced superconducting coil provided by the present invention;

In all the drawings, the same reference numerals are used to denote the same elements or structures, wherein 1 is ice for reinforcement, 2 is a coil bobbin, 3 is a superconducting coil, and 4 is a container.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not constitute a conflict with each other.

Fig. 1 is the flow chart of the insulation strengthening method of the superconducting coil provided by the present invention, as shown in Fig. 1, comprising the following steps:

S101, injecting water into the container where the superconducting coil is located until the superconducting coil is completely submerged in water;

S102, cooling the water to freeze until the water is completely condensed into ice, the ice is used to reinforce the superconducting coil, and the stress generated by ice shrinkage on the superconducting strip during the cooling process does not exceed the superconducting coil. The limit of the stress that the strip can withstand is such that ice does not cause the critical current of the superconducting coil to decay. The superconducting strip is used to wind the superconducting coil, and the superconducting coil works under low temperature conditions.

Specifically, in view of the problems existing in the reinforcement of the above-mentioned superconducting magnets, the present invention proposes a method for reinforcing superconducting magnets with ice, which includes the following steps:

1) placing the superconducting magnet to be reinforced in the containing device;

2) Inject water into the holding device until the magnet is completely submerged;

3) Leave the entire holding device still until the water completely impregnates the entire magnet;

4) Gradually lower the temperature of the entire device until the water is completely solidified into ice, and the reinforcement of the magnet is completed

Specifically, the strengthening process of the magnet is carried out step by step as the temperature of the magnet decreases.

As a preference: the water is preferably degassed water, and at the same time avoid generating air bubbles as much as possible during the cooling and freezing process of the water.

As a preference: the cooling and freezing rate should be slow enough to avoid cracks during the cooling and freezing process, which will affect the mechanical properties of the ice.

As a preference: let the water fully impregnate the magnet before cooling down, and let the water fill the gaps between the strips.

As a preference: the thickness of the ice for reinforcement is moderate, which can not only play the role of insulation reinforcement, but also not affect the thermal stability.

As a preference: the reinforcement method of ice is suitable for the reinforcement of low-temperature superconducting magnets such as NbTi and NbSn3 and high-temperature superconducting magnets such as YBCO and iron-based superconductors.

It should be noted that the high temperature superconducting magnet works at a temperature of about 77K, compared with the low temperature superconducting magnet working at a temperature of 4K, it still needs to work at a low temperature.

As a preference: glass fiber, cotton, hemp, chloroform, antifreeze and other substances can be added to the water to increase the mechanical strength and insulating properties of the ice.

As a preference: the ice reinforcement method is suitable for the reinforcement of superconducting magnets in open containers or closed containers. For the reinforcement of magnets in closed containers full of water, ice will generate a greater prestress.

Fig. 2 is a structural diagram of the ice-reinforced superconducting coil provided by the present invention. As shown in Fig. 2, 1 is the ice for reinforcement, 2 is the coil frame, 3 is the superconducting coil, and 4 is the container. The coil reinforcement method in the present embodiment comprises the following steps:

1) Place the wound superconducting coil 3 in the container 4 .

2) Fill the container 4 with water until the coil 3 is completely submerged.

3) Let the whole device stand still to allow water to fully fill the space inside the coil 3 and impregnate the entire coil 3 .

4) Gradually lower the temperature of the entire device until the water is completely condensed into ice 1 to realize the reinforcement and insulation of the coil 3 .

If bubbles and cracks are generated during the cooling process or during the experiment, the method for repairing insulation fatigue in this embodiment includes the following steps:

1) Return the ice-strengthened superconducting coil to normal temperature.

2) After repeating the cycle from step 2) to step 4) of the above reinforcement process, the superconducting coil 3 completes the reinforcement of the mechanical structure again.

It should be understood that the present invention proposes a new superconducting coil strengthening method, and the disclosed embodiment is only an example of the present invention. Using ice to reinforce the superconducting coil by adopting the thought disclosed in the present invention should belong to the protection scope of the present invention.

It is easy for those skilled in the art to understand that the above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention, All should be included within the protection scope of the present invention.

Claims (6)

1. A method for strengthening insulation of a superconducting coil, comprising the following steps: Pour water into the container where the superconducting coil is located until the superconducting coil is completely submerged in water; The water is cooled until the water is completely condensed into ice, and the ice is used to reinforce the superconducting coil, and the stress generated by ice shrinkage on the superconducting strip during the cooling process does not exceed the stress limit that the superconducting strip can bear , so that the ice does not cause the critical current decay of the superconducting coil, the superconducting tape is used to wind the superconducting coil, and the superconducting coil works under low temperature conditions. 2. The insulation strengthening method according to claim 1, characterized in that the cooling rate must be lower than a preset threshold to avoid cracks during cooling and icing, which will affect the mechanical properties of the ice. 3. The method for strengthening insulation according to claim 1 or 2, characterized in that the water is deaerated water. 4. The insulation strengthening method according to claim 1 or 2, characterized in that the method further comprises the steps of: Before cooling the water, let the water fully soak the superconducting coils, and let the water fill the gaps between the superconducting strips. 5. The method for strengthening insulation according to claim 1 or 2, characterized in that air bubbles are avoided during the cooling and freezing process of water. 6. The insulation strengthening method according to claim 5, characterized in that the method further comprises the steps of: If the water produces bubbles or cracks in the ice during cooling, return the ice-reinforced superconducting coil to normal temperature; Expelling the gas in the water, or pouring out the water in the container where the superconducting coil was originally located, and re-adding degassed water into the container until the superconducting coil is completely submerged in water; The water is again cooled to freeze until the water is completely condensed into ice.