JPS62108507A - Superconducting coil - Google Patents

Abstract

PURPOSE:To increase the effective inner diameter of a superconducting coil by winding a superconducting lead by applying a tension which is large at the inside of the coil and small at the outside of the coil to the lead at winding time to reduce the thickness of a coil spool. CONSTITUTION:When a winding tension is varied according to the position of a layer so as to be strong at the inner layer side and weak at the outer layer side, the radial compressing force 2 applied to a winding blank becomes strong at the inner layer side and weak at the outer layer side. Accordingly, when the compressing force of each layer in case of applying an electromagnetic force generated by the energization becomes a predetermined value or higher, the wire blanks 3 or the blank 3 and the spool 1 are fixed with a predetermined value or larger compressing force. Accordingly, the blank does not move radially nor move axially by a stationary frictional force to eliminate a quench due to the movement of the blank. Thus, the compressing force applied to the coil spool 1 is reduced smaller than that of a coil wound in all layers by the tension of the innermost layer to reduce the thickness of the spool, thereby increasing the effective inner diameter.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a superconducting coil formed by winding a superconducting wire around a coil frame.

[Technical background of the invention and its problems]

When winding a superconducting wire around a coil frame, it is usually done while applying a certain tension to the superconducting wire.

One of the reasons for winding with tension in this way is to improve workability during winding, and another reason is to prevent the coil from spreading in the radial direction, which occurs when electricity is applied to the wound coil. This is to give the superconducting wire a force to resist the force in advance. If the tension during winding is too weak, the wire will not be fixed to the winding frame or the outer layer wire to the inner layer wire, and electromagnetic waves will occur in the radial or axial direction when energized. The force makes the conductor easier to move. This movement of the conductor causes the superconducting coil to quench, and the coil often quenches at a current that is considerably lower than the maximum current that can be passed through the superconducting wire. It is also said that the training phenomenon, in which the current quenches and increases each time it is energized, occurs when the wire moves toward a stable position in the superconducting coil.

In order to prevent these phenomena from occurring, it is possible to increase the tension during winding, but in order to increase the winding tension, the thickness of the winding frame must be increased and the material that makes up the winding frame must be increased. must be prevented from surrendering.

Used in the winding frame of superconducting magnets that require a highly uniform magnetic field.
When using materials with low elastic limits such as non-magnetic aluminum alloys and PRP, the wall thickness of the winding frame must be made considerably thicker, which reduces the effective inner diameter of the coil and increases the amount of liquid helium required to cool the coil. This may cause inconveniences such as

[Purpose of the invention]

This invention improves the above-mentioned drawbacks of superconducting coils, and aims to eliminate coil quench caused by conductor movement, and to obtain a superconducting coil with a thin coil winding frame and a large effective inner diameter. .

[Summary of the invention]

The tension applied to the wire when winding the superconducting wire around the coil frame is
By making the coil stronger on the inner diameter side and weaker on the outer diameter side,
Reduce the force applied to the coil winding frame.

〔Effect of the invention〕

By implementing the present invention, it is possible to eliminate quench caused by the movement of the conductor, and it is possible to apply the maximum current that can flow through the wire to the superconducting coil, thereby eliminating the training phenomenon.

Additionally, since the coil winding frame can be made thinner, the amount of liquid helium required for cooling can be reduced, and the effective inner diameter of the coil can be increased using the same amount of wire. .

[Embodiments of the invention]

An embodiment of the invention is shown in FIG. The force that occurs when the solenoid coil is energized and tends to spread in the radial direction is
Larger in the inner layer and smaller in the outer layer.

In an infinite length solenoid coil, the distribution of radial electromagnetic force is linear and zero at the outermost diameter of the coil.

Even with a finite length solenoid coil, the radial electromagnetic force distribution is approximately linear, with the maximum at the innermost layer and the minimum at the outermost layer. The electromagnetic force in the outermost layer is directed inward in the radial direction. Therefore, as shown in Fig. 1, if the winding tension is changed depending on the layer position, and the wire is wound strongly on the inner M side and weakly on the outer layer side, the radial compressive force 2 applied to the wire is also strong on the inner layer side and on the outer layer side. It becomes weaker. Therefore, if the compressive force in each layer is set to exceed a certain value when electromagnetic force generated by energization is applied, the wire 3 or the wire 3 and the winding frame 1 will have a compressive force above a certain value. Since it is fixed, it does not move in the radial direction, and can be prevented from moving in the axial direction with a locking force. Therefore, quenching due to movement of the wire can be eliminated in this way.

Compared to conventional coils in which all layers are wound with the tension of the innermost layer, the compressive force applied to the coil winding frame 1 is smaller, making it possible to reduce the thickness of the winding frame, and
The effective inner diameter can be increased.

The distribution of winding tension may be on a straight line, or the optimum tension may be given by taking into consideration the distribution of electromagnetic force in the axial direction and the magnitude of the stopping force. Furthermore, it is also possible to give the optimum tension by taking into account the difference in thermal contraction between the winding frame and the wire when cooled to liquid helium temperature.

Further, the winding tension may be changed for each layer or for every several layers.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a superconducting coil showing an embodiment of the present invention;
FIG. 2 is a schematic cross-sectional view of a conventional superconducting coil. 1... Superconducting coil winding frame 2... Compressive stress applied to the wire due to winding tension 3...
Superconducting wire agent Patent attorney Nori Chika Yudo Kikuo Takehana

Claims (1)

[Claims] A superconducting coil formed by winding a superconducting wire around a coil winding frame, characterized in that the tension applied to the superconducting wire at the time of winding is large at the inner diameter of the coil and smaller at the outer diameter of the coil. .