JPS5857884B2 - Manufacturing method of superconducting electromagnet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a superconducting electromagnet, and in particular to a process for tightening electromagnet windings.

As is well known, a superconducting wire transitions from a superconducting state to a normal conducting state when the wire temperature, applied magnetic field, and wire current flow exceed certain values (referred to as critical values).

Therefore, in order to effectively utilize the superconducting wire, it is necessary to be able to conduct current up to a value shown by the magnetic field H-critical current Ic characteristic in a short length of the superconducting wire, the so-called short length H-Ic characteristic.

However, the value decreases due to various causes.

For example, in an electromagnet manufactured by winding a superconducting electromagnet winding 2 under tension around a coil bobbin 1 in which a cylindrical part 1a and a flange part 1b are integrally formed as shown in FIG. It is about 60-70% of the short length characteristic,
It is known that the main cause of this is the movement of the wound superconducting wire during excitation.

That is, when the electromagnet manufactured as described above is excited in refrigerant helium, a strong electromagnetic force as shown by the arrow in Fig. 2 is applied, so that the electromagnet winding 2 is moved in the axial direction as shown by the broken line. is deformed so that it contracts and expands in the radial direction.

Among these forces, the expansion force in the radial direction can be prevented from deformation and movement of the wire by applying tension to the wire and tightening the wire during conduction.

However, in response to compressive force in the axial direction, it is technically difficult to wind the wire in close contact with the winding, so movement tends to occur, and when observed after excitation operation, the coil bobbin 1
A gap may be seen between the flange portion 1b and the flange portion 1b.

In other words, the superconducting wire moves, which leads to deterioration of superconducting properties.

In order to overcome this drawback, in recent years a method has been used in which the winding portion of a superconducting electromagnet is impregnated with epoxy resin or the like to stop the movement of the wire and bring the current value closer to the value of the short length characteristic.

According to this method, it is possible to achieve 85 to 100% of the short length characteristics, but on the other hand, the following problems arise.

(1) Since the entire electromagnet is wrapped in epoxy resin, etc., contact with the refrigerant is cut off and cooling takes time.Also, when heat is generated in the superconducting winding for some reason. The operation of the electromagnet becomes unstable.

(2) If a part of the superconducting wire burns out or breaks due to an accident, or if you want to change the shape of the electromagnet, the epoxy resin impregnated with it cannot be removed, making the superconducting wire expensive. This makes it impossible to reuse the coil bobbin, etc., which is uneconomical.

An object of the present invention is to provide a manufacturing method that eliminates the above-mentioned drawbacks of the prior art and allows a stable and economical superconducting electromagnet to be obtained.

In order to achieve this object, the present invention makes at least one flange of a coil bobbin movable in the axial direction, excites the electromagnet winding in a cryogenic temperature, and uses the electromagnetic force generated at this time to move the electromagnet winding along its axis. The flange is moved to tighten and fix the electromagnet winding.

An embodiment of the present invention will be described below with reference to FIG.

The coil bobbin used in this example consists of a cylindrical part 1a and a flange part 1b fitted to both ends of the cylindrical part 1a so as to be able to move in the axial direction. Tightening is done by a nut 3.

A superconducting electromagnet winding 2 is wound around a coil bobbin having such a structure to create a superconducting electromagnet, and this is immersed in the refrigerant liquid filled in the cryostat 4 into the ram 5. Threaded part (or left-handed threaded part)
6a and the left-hand threaded portion (or right-handed threaded portion) 6b are held by a plate 7 via an adapter 8.

In Figure E, 9 is the flange of the cryostat, 10
The tightening is a fixed loft to prevent rotation of the plate 8.

Next, the electromagnet winding 2 of the superconducting electromagnet held in such a cryogenic temperature is energized to excite it and compressed in the axial direction, and tightening is carried out by rotating the shaft 6 from the outside. Both tightening moves the plates 7 toward each other,
Both flange portions 1b of the coil bobbin are moved, and the electromagnet winding 2 is tightened from both sides in the axial direction by these flange portions 1b.

When the electromagnet winding is tightened in this way, a gap is created between the flange part 1b and the nut 3, so take them out to room temperature and tighten the nut 3 so that the flange part 1b is connected to the electromagnet winding. Make sure that it does not loosen relative to line 2.

In this case, when the refrigerant liquid helium 5 is taken out to room temperature, it is conceivable that the once tightened material may loosen due to the difference in the coefficient of thermal expansion of each component.

To avoid this, tighten the adapter 8 using a material with a coefficient of thermal expansion larger than that of the shaft 6. For example, if the shaft 6 is made of stainless steel, tighten the adapter 8 with a material that has a coefficient of thermal expansion several times that of stainless steel. It is best to make it from a certain kind of epoxy resin material.

In this way, the superconducting electromagnet winding portion can be more strongly tightened when the refrigerant is taken out from the extremely low temperature refrigerant to the room temperature.

The superconducting wire in the superconducting electromagnet manufactured in this manner has a current carrying capacity of 95 to io, which is a short characteristic.

It has been confirmed through experiments that this can be achieved.

Note that it may be more effective to further impregnate the superconducting electromagnet produced as described above with an epoxy resin or the like, depending on the purpose of its use.

Further, in the above-mentioned experimental example, the refrigerant helium immersion method was described, but it goes without saying that it can also be applied to forcibly cooled electrical equipment such as hollow conductors.

Furthermore, it goes without saying that the present invention is widely applicable not only to the solenoid type electromagnet described in the experimental example but also to electromagnets of special shapes.

As explained above, according to the present invention, a superconducting electromagnet with stable superconducting properties without any movement of the superconducting wire can be obtained, and since the superconducting wire, coil bobbin, etc. can be easily disassembled, the design can be changed as many times as necessary. It can be reassembled and repaired in the event of a breakdown, making it extremely economical.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view of a conventional superconducting electromagnet using a coil bobbin with an integral cylindrical part and a flange part, and Fig. 2 is an explanatory diagram showing the direction of electromagnetic force applied to the winding part when the superconducting electromagnet is excited. FIG. 3 is a sectional view of a manufacturing apparatus used to carry out the manufacturing method of the present invention. 1a... Cylindrical part of the coil bobbin, 1b...
... Flange part of coil bobbin, 2 ... Superconducting electromagnet winding, 3 ... Flange tightening with nut, 5
...Liquid helium, 6...Tighten with shaft, 7...Tighten with plate.

Claims (1)

[Claims] 1. A method for manufacturing a superconducting electromagnet in which an electromagnet winding made of superconducting wire is wound around a coil bobbin having flanges at both ends, in which at least one of the flanges is made movable in the axial direction of the coil bobbin, and the electromagnet winding is wound in an extremely low temperature. A method for manufacturing a superconducting electromagnet, characterized in that the electromagnet winding is compressed in its axial direction by the electromagnetic force at this time, and the flange is moved to tighten and fix the electromagnet winding.