JPS6057688B2 - Pancake wrapped superconducting coil - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pancake-wound superconducting coil, and particularly relates to a coil bobbin, a unit coil wound in a pancake shape around the coil bobbin and provided in multiple stages, and a superconducting coil formed between the unit coils. The present invention relates to an improvement in a pancake-wound superconducting coil configured to include a cooling channel.

Conventionally, a pancake-wound superconducting coil as shown in FIG. 1 has been known.

This pancake-wound superconducting coil, as shown in the figure,
A coil bobbin 4 having a coil shaft 2 and a coil bobbin 4
The coil winding portion 8 is wound around the coil with a cylindrical insulating plate 6 interposed therebetween. As shown in FIG. 2, the coil winding section 8 winds a superconducting wire 14 with a rectangular cross section and an insulator 12 on one side from its midpoint to the side surface of the coil bobbin 4, with one layer winding to the right (left) and the other winding to the right (left). It is constructed by providing a plurality of stages of unit coils, that is, pancake-shaped unit coils 10, which are made up of two layers in which one layer is wound in a left-handed (right-handed) manner. Therefore, this unit coil 10 has a flat plate shape, and each bottom surface is perpendicular to the coil axis 2. In the gaps between the layers of the unit coils 10 and between the unit coils 10,
A cooling channel 16 extending radially from the side surface of the coil bobbin 4 is formed by inserting an insulating spacer (not shown) extending radially from the side surface of the coil bobbin 4 .
So, unit coil 1? A flange 18 is attached to both bottom surfaces of the coil winding section 8, which is configured by providing multiple stages of the coil winding section 8, with a donut-shaped insulating plate 7 interposed therebetween. A pancake-wound superconducting coil is created by compressing with bolts 22 and finishing the coil winding portion 8 to predetermined dimensions.

However, such pancake-wound superconducting coils generally have the problem that the unit coils cannot be tightly wound, and the windings move due to the electromagnetic force generated when the coil is excited, making the superconducting state unstable. .

Therefore, there is a problem that the number of repeated excitations is increased until the critical current of the superconducting coil is achieved. In addition, when such a superconducting coil is used with the coil axis vertical and immersed in a coolant such as liquid helium, the bottom surface of each unit coil becomes horizontal, which reduces the excitation loss that occurs when the coil is excited, and the superconductor. Refrigerant bubbles 21 vaporized by heat generated in the coil due to instability such as Joule heat
remains in the cooling channels and significantly impedes cooling of the coil. For this reason, there is a problem in that superconductor breakdown often occurs during the process without achieving the intended purpose. The present invention has been made to solve the above problems, and an object of the present invention is to provide a pancake-wound superconducting coil in which the superconducting state is stable.

The present invention provides a pancake-wound superconducting coil configured to include a coil bobbin, unit coils wound in a pancake shape around the coil bobbin and provided in multiple stages, and cooling channels formed between the unit coils. The above object is achieved by slanting each bottom surface of the unit coil along the side surface of the truncated cone.

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 3 shows a first embodiment of the present invention. The figure shows a partially enlarged view of the coil winding part, and parts corresponding to those in FIG. 2 are denoted by the same reference numerals, and their explanations are omitted. As shown in the figure,
The bottom surface of each layer of the unit coil 10 of this embodiment is formed along the side surface of a truncated cone. Therefore, the cooling channels 16 formed between each layer of the unit coils 10 and between the unit coils 10 are similarly formed along the side surface of the truncated cone. That is, the cooling channel is formed on a curved surface that is inclined at a constant angle with respect to a plane perpendicular to the coil axis. In this way, in order to form each bottom surface of the unit coil 10 along the side surface of the truncated cone, the coil winding part 8 (the first
between one bottom surface of the flange 18 and the middle. A truncated conical insulating plate having a through hole in the center into which the coil bobbin is inserted is sandwiched, and the bottom surface has a through hole in the center into which the coil bobbin is inserted between the other bottom surface of the coil winding part and the flange. An insulating plate having a truncated conical concave portion may be held in between and tightened with a tightening bolt, a tightening nut, or the like.

By doing so, each layer of each unit coil constituting the coil winding portion is shifted, and each bottom surface of each unit coil is formed along the side surface of the truncated cone. According to this embodiment,
By tightening the unit coils wound in a flat plate shape, each bottom surface was formed to follow the side surface of the truncated cone, giving elongation to the wound wire itself and increasing the winding tension to form the unit coils. This allows for dense winding.

Therefore, instability caused by movement of the winding can be suppressed. In addition, when using this embodiment with the coil axis vertical, the cooling channel will be inclined upward with respect to the horizontal plane, and even if the refrigerant evaporates and bubbles are generated, the bubbles will be The refrigerant moves in the direction of the arrow shown in FIG. 3, and as it moves, the refrigerant also begins to undergo natural convection. Therefore, air bubbles do not remain in the coil winding portion, and the cooling effect is significantly improved. In this case, if the air bubbles flowing out from the coil winding portion are concentrated on the coil bobbin side, it is necessary to provide an air bubble outlet in the coil bobbin and the insulating plate around the coil bobbin. Next, a conventional superconducting coil with a flat unit coil and the superconducting coil of the first embodiment having the same superconducting wire, coil dimensions, and number of turns as this superconducting coil are fabricated, and the critical current of these superconducting coils is determined. The excitation was repeated until it was achieved.

The results are shown in Figure 4. In the figure, the number of excitations is taken on the horizontal axis, and the value obtained by dividing the current flowing when superconducting breakdown occurs at each excitation by the critical current of the superconducting coil is taken on the vertical axis. B shows the results for a conventional superconducting coil. As can be understood from the figure, the superconducting coil of this example shows a high value from the first time, and reaches the critical current value even if the number of excitations is small. FIG. 5 shows a second embodiment of the present invention.

In FIG. 5, parts corresponding to those in FIG. 1 are designated by the same reference numerals, and their explanations are omitted. In this embodiment, a first unit coil group 24 composed of multiple stages of unit coils inclined along the side surface of a truncated cone is symmetrical to the first unit coil group 24 with respect to a plane perpendicular to the coil axis 2. The coil winding portion is divided into a second unit coil group 26 which is inclined so that The first unit coil group 24 and the second unit coil group 24
Between the unit coil group 26 and the unit coil group 26, there is a so-called abacus-shaped insulating plate 28 which joins the bottom surfaces of two truncated cones and has a through hole penetrating from one top bottom surface to the other top bottom surface. is being held. The coil bobbin 4 is inserted into the through hole of the insulating plate 28. Furthermore, between the first unit coil group 24 and the flange 18 and between the second unit coil group 26 and the flange 18, there is an insulating plate 30 in the shape of a cylindrical column with a truncated conical cutout on one bottom surface. being held in place. By tightening the coil windings and insulating plates arranged as described above with tightening bolts, tightening nuts, etc., a group of unit coils is formed that is symmetrically inclined with respect to a plane perpendicular to the coil axis. A superconducting coil is created.

By the way, when a superconducting coil is excited, the electromagnetic force that acts on the coil winding part consists of a component directed from the coil axis toward the outer circumference of the coil winding part, and a component directed in a direction compressing the coil winding part in the coil axis direction. Become.

When these components are combined, it becomes a force in the direction of arrow F in FIG. Further, this force takes a maximum value on the side closest to the coil bobbin on a plane perpendicular to the coil axis and dividing the coil winding portion into two equal parts. However, the unit coils of this embodiment are all inclined in the direction in which the electromagnetic force acts,
An insulating plate 28 is provided at a portion where the maximum electromagnetic force acts. That is, the unit coils are deformed in advance to a state where they are deformed by electromagnetic force, and no unit coils are present in the portion where the maximum electromagnetic force is applied. As described above, the present embodiment is densely wound like the unit coil of the first embodiment, knitted to be deformed in advance, and there is no unit coil in the part where the maximum electromagnetic force is applied. Therefore, movement of the wire due to electromagnetic force is suppressed, and a stable superconducting state can be obtained.

Furthermore, since the cooling channel is inclined, an excellent cooling effect can be obtained even when the coil axis is used vertically. As explained above, according to the present invention, the superconducting state is stabilized and an excellent cooling effect can be obtained.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing the left half of a conventional pancake-wound superconducting coil, Fig. 2 is a partially enlarged view showing the coil winding portion of a conventional pancake-wound superconducting coil, and Fig. 3 is an explanatory diagram showing the left half of a conventional pancake-wound superconducting coil. FIG. 4 is a diagram showing the relationship between the ratio of the superconducting breakdown current to the superconducting critical current and the number of excitations, and FIG. 5 is a partial enlarged view showing the coil winding part of the first embodiment of the present invention. It is an explanatory view showing the left half of an example. 4... Coil bobbin, 8... Coil winding section, 10... Unit coil, 16...
Cooling channel, 24...first unit coil group, 26...second unit coil group.

Claims (1)

[Claims] 1. A pancake that includes a coil bobbin, unit coils wound around the coil bobbin in a pancake shape and provided in multiple stages, and cooling channels formed between the unit coils. A pancake-wound superconducting coil characterized in that the bottom surface of each of the unit coils is inclined along a side surface of a truncated cone. 2. The unit coil is divided into two into a first unit coil group and a second unit coil group on a plane perpendicular to the axis of the coil bobbin, and the bottom surface of each unit coil constituting the first unit coil group and the The pancake-wound superconducting coil according to claim 1, wherein the bottom surfaces of the unit coils constituting the second unit coil group are inclined symmetrically with respect to a plane perpendicular to the axis of the coil bobbin.