JP2006117184A - Ground coil device for magnetic levitating type railway - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance propulsion efficiency by reducing eddy current loss of a propulsion coil and to reduce power consumption. <P>SOLUTION: The ground coil device is installed on a track for a magnetic levitating type railway and is constituted by winding a cable. In the used cable 31, a twisted wire conductor 33 is constituted by twisting a plurality of element wires 32 in which an insulation material 32b is covered on a naked element wire 32a. An inner semiconductive layer 34, an insulation layer 35 and an outer semiconductive layer 36 are formed on a periphery of the twisted wire conductor 33 in the order from the inner side. A sheath buried with a wire shield 37 is further formed on the periphery. The eddy current is induced on the twisted wire conductor 33 by variation magnetic field by an ultra-conductive magnet at a vehicle side, however, since the element wire 32 of the twisted wire conductor 33 is the insulation element wire, the eddy current induced on the twisted wire conductor 33 is suppressed and the eddy current loss is reduced. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a ground coil device installed on a magnetically levitated railway track.

  As a magnetic levitation railway, a method of moving the vehicle at high speed without contact with the track by applying a levitating force and propulsive force to the vehicle by electromagnetic interaction between the superconducting magnet and the coil laid on the ground side. A superconducting magnetic levitation railway is being put into practical use. FIG. 4 shows an arrangement of a propulsion coil 1 that gives propulsive force to a vehicle, that is, a linear motor coil, among the coils on the ground side in this type of magnetic levitation railway track (guideway). As shown in the figure, propulsion coils 1 of U, V, and W phases of three-phase alternating current are sequentially arranged along the longitudinal direction of the track. The propulsion coil 1 of each phase in the illustrated example is connected to the three phases of the power source by sequentially connecting with the lead cable 3 via the connection portion 2 for each phase.

  When the above-described propulsion coil 1 is configured, as shown in FIG. 5, a plurality of propulsion coils 6 wound by a necessary number of turns and lead wire portions 7 between the respective propulsion coils 6 are connected to one cable 8. It has been proposed to use it (see Fig. 1 in Japanese Patent Application No. 1-261680). Each propulsion coil 6 is bound by a bind 9 at a plurality of locations. The propulsion coil 6 shown in FIG. 5 is a one-phase propulsion coil of three-phase alternating currents U, V, and W, and is arranged so that the propulsion coils of each phase of U, V, and W are arranged in order. The

As a cable used for this type of cable-type propulsion coil 6 formed by coiling the cable 8 as described above, a general cross-linked polyethylene power cable, that is, a bare wire as shown in FIG. An inner semiconductive layer 12, an insulator layer 13 made of dry-crosslinked polyethylene, and an outer semiconductive layer 14 are formed around the stranded wire conductor 11 in which 11a is twisted, and a metal shielding layer 15 is formed on the outer periphery thereof. There has been proposed a power cable in which a sheath 17 is formed on the outer periphery of the outer periphery which is disposed and pressed by a pressing tape 16 (Japanese Patent Application No. 8-5976).
Japanese Patent Application No. 1-261680 Japanese Patent Application No. 8-5976

When the general cross-linked polyethylene cable 10 is used as the propulsion coil as described above, the propulsion coil installed on the magnetic levitation railway track is applied with the strong magnetic field of the superconducting magnet mounted on the vehicle. Eddy currents are induced in the stranded wire conductor 11 and the shielding metal layer 15, and the loss due to the eddy current, particularly the eddy current loss in the stranded wire conductor 11 made of the bare wire 11a, reduces the propulsion efficiency and reduces the power consumption of the linear motor. There was a problem of increasing.
In addition, since the cross-linked polyethylene cable has a low allowable flexibility and a large allowable bending radius, the window area of the coil cannot be increased. Therefore, there is a problem that the thrust characteristic of the coil is low and the propulsion efficiency is low.

  The present invention has been made to eliminate the above-mentioned conventional drawbacks, and it is intended to obtain a magnetic levitation railway ground coil device capable of reducing eddy current loss, improving propulsion efficiency, and reducing power consumption. Main purpose. Furthermore, it is possible to reduce the allowable bending radius of the cable and reduce the size of the propulsion coil.

  Invention of Claim 1 which solves the above-mentioned subject is a ground coil device for a magnetic levitation type railway, around a stranded wire conductor formed by twisting a plurality of strands covered with an insulating material on a bare strand, An internal semiconductive layer, an insulating layer, and an external semiconductive layer are formed in order from the inside, and a cable in which a metal shielding layer and a sheath are formed around the inner semiconductive layer is used.

The invention of claim 2 is a magnetic levitation railway ground coil device, in which a plurality of strands in which a bare strand is coated with a semiconductive material having a resistivity of 10 ⁻¹ to 10 ⁶ Ω · cm are twisted together. A cable in which an inner semiconductive layer, an insulating layer, and an outer semiconductive layer are formed in this order from the inside around a stranded wire conductor formed thereon, and a metal shielding layer and a sheath are formed around the inner semiconductive layer.

According to a third aspect of the present invention, in the magnetic levitation railway ground coil device according to the first or second aspect, the insulating material or semiconductive material of the wire is a low melting point resin.
A fourth aspect is characterized in that the low melting point resin in the third aspect is a urethane resin.

  According to a fifth aspect of the present invention, in the magnetic levitation railway ground coil device according to the first to fourth aspects, at least a part of the strands of the outermost layer in the stranded conductor is replaced with an uncovered bare strand. .

  According to a sixth aspect of the present invention, in the magnetic levitation railway ground coil device according to the first to fifth aspects, the insulating layer is an insulating layer made of a rubber-based insulating material.

The magnetic levitation type railway ground coil device according to any one of claims 1 to 6, wherein the metal shielding layer is arranged in parallel and spirally with a plurality of metal wires on the outer periphery of the outer semiconductive layer at intervals. It is characterized by being a wire shield.
An eighth aspect of the present invention is the magnetic levitation railway ground coil device according to the seventh aspect, wherein the wire shield is embedded in a sheath made of resin.

  The levitation current is induced in the cable conductor of the propulsion coil because the strong fluctuating magnetic field of the superconducting magnet on the vehicle side is applied to the propulsion coil of the magnetic levitation railway track. According to the upper coil device, the strands constituting the stranded conductor of the cable to be used are not mere bare strands, but are insulated strands in which an insulation material is coated on the bare strands. The current is suppressed. In other words, in the case of a stranded conductor made by simply twisting bare strands, a large eddy current is generated by an eddy current that is induced by the fluctuating magnetic field generated by the superconducting magnet on the vehicle side. Although the loss increases, in the case of a stranded wire conductor in which insulating strands are twisted, an eddy current is induced in each insulating strand, so that a large eddy current does not occur and the eddy current loss does not increase. Therefore, the reduction in propulsion efficiency is reduced, and the power consumption of the linear motor can be reduced.

Even if a bare wire that has a resistivity of 10 ⁻¹ to 10 ⁶ Ω · cm semiconductive material is used as a strand constituting the stranded wire conductor, it is induced in the stranded wire conductor. The effect of suppressing generated eddy currents can be effectively achieved.

When the propulsion coil is installed on the side wall of the guideway, the propulsion coils need to be connected to each other. However, when the strand of the stranded conductor is an insulating strand, it is necessary to remove the insulating coating.
When using polyester, ester imide, formal, etc., which are generally used as insulation materials for winding conductors used in motors and transformers, as the insulation coating for strands, these materials are often excellent in heat resistance, Since it cannot be easily removed unless chemicals are used and further heated, the connection work is very laborious and unrealistic.
However, if a low melting point resin is used as the insulation material of the wire as in claim 3, the insulation coating can be easily removed by dipping into a solder bath or the like, and the workability of connecting the propulsion coils is improved. Remarkably improved.
Among low-melting-point resins, urethane resin is particularly suitable as an insulating material for strands because it is easily peeled off by dipping into a solder bath as compared with polyester, ester imide, formal and the like.
The same applies to the case where a semiconductive material is coated instead of an insulating material, and a low melting point resin, particularly a urethane resin, is suitable as the semiconductive material.

Further, as in claim 5, by making at least a part of the outermost strand in the stranded conductor into an uncovered bare strand, the stranded conductor can have the same potential as the inner semiconductive layer. Thus, the action of the internal semiconductive layer that equalizes the electric field is effectively achieved.
Eddy currents are also induced in the metal shielding layer by the fluctuating magnetic field generated by the superconducting magnet on the vehicle side. As in claim 7, a plurality of shield strands are arranged in parallel at intervals on the outer periphery of the outer semiconductive layer. If the metal shielding layer is configured by the wire shield arranged in a spiral shape, eddy current can be suppressed and the eddy current loss is less than that of the metal shielding layer having a braided structure. In other words, a large eddy current is easily induced in a braided structure in which a conductive path in the cable circumferential direction is formed, which increases eddy current loss. However, a large eddy current is induced in a wire shield in which each metal wire is wound in a separated state. The eddy current loss is small.

  Since the bending radius of the cable of the propulsion coil is extremely small, sufficient flexibility is required for the cable to be used, but the allowable bending radius of the single-core cable whose insulation is cross-linked polyethylene is at least about 8 times the outer diameter. And is not necessarily flexible enough for the cable of the propulsion coil. However, as described in claim 6, by using a rubber-based insulating material for the insulator, the allowable bending radius can be reduced to about four times the outer diameter. Therefore, the window area of the coil can be increased and the thrust generated with the same propulsion current can be increased, so that the propulsion efficiency can be improved.

Since the bending radius of the cable of the propulsion coil is extremely small as described above, when the wire shield as in claim 7 is formed as the metal shielding layer, the metal wire moves in the circumferential direction and is biased toward the distribution of the metal wire (circular There is a risk that the shielding performance will be reduced, and that eddy currents may increase due to contact with each other. In addition, a biased metal wire sandwiches the outer semiconductive layer. There is a possibility that the effect of making the electric field uniform by the deformation is lowered. As described above, since the electrical characteristics of the cable may be impaired, the bending radius of the cable of the propulsion coil cannot be sufficiently reduced.
However, when the wire shield is embedded in the sheath resin as in claim 8, even when the cable is bent with an extremely small bending radius, the movement of the metal wire in the circumferential direction does not occur, and the interval between the metal wires is reduced. Kept constant. Therefore, there is no risk of uneven distribution (circumferential density) in the metal wires, contact with each other, or deformation of the outer semiconductive layer, and there may be a decrease in shielding performance, an increase in eddy currents, or an electric field. There is no problem of damaging the electrical characteristics, such as a reduction in the action of equalizing, and the bending radius of the cable of the propulsion coil can be made sufficiently small.
In addition, when winding a metal wire directly on the outer peripheral surface of the outer semiconductive layer, a press-wound tape is required and its winding is complicated, but when a metal wire is embedded in a sheath resin, a press-wound tape is not required, The manufacturing process is simplified.
If the metal shielding layer is made of a metal tape, the rigidity is increased and the flexibility of the cable is lowered. However, according to the wire shield wound with the metal wire, the flexibility is lowered as compared with the case of the metal tape. Can be avoided.
In addition, when the metal shielding layer is composed of a braid, a large eddy current is likely to be induced in the braid structure in which a conductive path in the cable circumferential direction is formed, which increases eddy current loss, but each metal wire is wound in a separated state. In the wire shield, a large eddy current is not induced and eddy current loss is small.

  Hereinafter, a magnetic levitation railway ground coil device embodying the present invention will be described with reference to the drawings.

  The magnetic levitation railway to which the magnetic levitation railway ground coil device of the present invention is applied has a levitation force and a propulsion force on the vehicle by electromagnetic interaction between a superconducting magnet on the vehicle and a coil laid on the ground side. This is a method of moving the vehicle at high speed without contact with the track. FIG. 3 schematically shows a track (guideway) of this magnetically levitated railway, and a propulsion coil 23 that gives propulsive force to the vehicle is attached to a concrete side wall 22 constituting the guideway 21. Although not described in detail above, a levitation / guide coil 24 for levitation / guidance of the vehicle is attached. Reference numeral 25 denotes a vehicle body, and 26 denotes a superconducting magnet provided on the vehicle body 25 side.

FIG. 2 schematically shows the arrangement of the propulsion coil 23 according to the embodiment. As shown in the figure, the propulsion coils 23 are arranged along the longitudinal direction of the orbit in order, such as three-phase alternating current U, V, and W propulsion coils 23. Each of the propulsion coils 23 in the illustrated example is a coil unit in which the connection cable portions 23a are continuously provided. The connection cable portions 23a of the respective coil units are connected to each other by the connection portion 28, and each propulsion coil 23 is Each phase is connected in sequence and connected to the three phases of the power supply. The voltage applied to the propulsion coil 23 is, for example, 10 to 35 kV.
In FIG. 2, the number of turns of the propulsion coil 23 is shown in a simplified manner, but a coil having a number of turns as necessary, such as several turns, is formed. Each propulsion coil 23 is sandwiched and fixed to the concrete side wall 22 by, for example, a mounting bracket 29 or a floating guide coil.
The propulsion coil 23 of the embodiment is a coil by lap winding as shown in FIG. Since the number of windings corresponding to one turn can be set to a plurality of times by overlapping winding, a high induced voltage can be obtained and the efficiency of the linear motor (linear synchronous motor) can be improved. When one phase is wave-wound with one cable, the equivalent number of turns is 1 turn. To increase the number of turns (number of conductors), the number of connections must be increased. In this case, since a single cable can form a plurality of turns, the efficiency of the linear motor can be improved without being complicated.

FIG. 1 (a) shows a cross-sectional view of a cable 31 constituting a ground coil device according to an embodiment of the present invention. As shown in FIG. 1 (b), the cable 31 constituting the ground coil device is formed by twisting a plurality of strands 32 in which an insulating material 32b is covered with a bare strand (wire consisting only of an electrical conductor) 32a. An inner semiconductive layer 34, an insulating layer 35 made of a rubber-based insulating material, and an outer semiconductive layer 36 are formed around the stranded conductor 33 in order from the inside, and a sheath 38 in which a metal shielding layer 37 is embedded around the inner semiconductive layer 34. It is a formed structure. The bare wire 32a is a copper wire or an aluminum wire. The strand diameter is 0.45 to 3.2 mmφ or the like, and the coating thickness of the insulating material 32b covering the bare strand is 0.001 to 0.1 mm or the like. The outer diameter of the cable 31 constituting the ground coil device is, for example, 20 mm to 50 mmφ.
Thus, since the strand 32 of the stranded conductor 33 is an insulated strand, the eddy current induced in the stranded conductor 33 by the fluctuating magnetic field by the superconducting magnet on the vehicle side is small, and therefore the eddy current loss does not increase. . Thereby, the fall of propulsion efficiency is reduced and the power consumption of a linear motor can be reduced.

  Of the strands 32 constituting the stranded conductor 33, some of the outermost layers, for example, several, are preferably bare strands. Thereby, the stranded wire conductor 33 can be set to the same potential as that of the internal semiconductive layer 34, and the action of the internal semiconductive layer 34 that equalizes the electric field is effectively achieved.

A low melting point resin may be used as the insulating material 32b of the strand 32, but a urethane resin is particularly preferable. That is, when the propulsion coil 23 is attached to the side wall of the guideway, connection between the propulsion coils 23 is necessary. In the illustrated case, the connecting cable portions 23a of the propulsion coil 23 are connected to each other. Since the strand 32 of the stranded conductor 33 in the cable 31 constituting the ground coil device has the insulation coating 32b, it is necessary to remove the insulation coating 32b of the strand 33 at the time of connection. When using polyester, ester imide, formal, etc., which are generally used as insulation materials for winding conductors used in motors and transformers, as the insulation coating for strands, these materials are often excellent in heat resistance, Since it cannot be easily removed unless chemicals are used and further heated, the connection work is very laborious and unrealistic.
However, when a low melting point resin, particularly urethane resin, is used as the insulation material of the wire, the insulation coating can be easily removed by dipping into the solder bath, and the workability of connecting the propulsion coils is significantly improved. A urethane resin is suitable as an insulating material for a wire because it is easily peeled off by dipping into a solder bath as compared with polyester, ester imide, formal and the like.

As the rubber-based insulating material constituting the insulating layer 35, for example, EP rubber (ethylene propylene rubber), Si rubber (silicon rubber) and the like are suitable.
The propulsion coil is required to have sufficient flexibility for the cable to be used because the bending radius of the cable is extremely small. However, the allowable bending radius of a single-core cable whose cross-linked polyethylene is an insulator is at least 8 times the outer diameter. This is not necessarily flexible enough as a cable for the propulsion coil. However, the allowable bending radius can be reduced to about four times the outer diameter by using, for example, EP rubber as the insulator. Therefore, the window area of the coil can be increased and the thrust generated with the same propulsion current can be increased, so that the propulsion efficiency can be improved.

The metal shielding layer 37 is a wire shield in which a plurality of metal wires 37a are arranged in parallel and spirally on the outer periphery of the external semiconductive layer 36, and the wire shield 37 is as described above. , Embedded in a sheath 38 made of resin.
Since the bend radius of the cable is extremely small as described above, the propulsion coil is a wire shield in which a metal wire is simply arranged in parallel and spirally at an outer periphery of the outer semiconductive layer 36 as a metal shield layer of the cable. If the metal wire is provided, the metal wire may move and the distribution of the metal wire may be biased (circumferential density), and in this case, the shielding performance may be deteriorated. Further, the metal wires may come into contact with each other. In this case, the eddy current is slightly increased as compared with the case where the metal wires are separated from each other. Further, there is a risk that a biased metal wire sandwiches the outer semiconductive layer and deforms it, and in this case, the deformation of the outer semiconductive layer may reduce the action of equalizing the electric field. As described above, since the electrical characteristics of the cable may be impaired, the bending radius of the cable of the propulsion coil cannot be sufficiently reduced.
However, when the wire shield 37 is embedded in the sheath resin 38 as in the embodiment, even when the cable is bent with a very small bending radius, the movement of the metal wire 37a does not occur, and the interval between the metal wires 37a is constant. Kept. Therefore, there is no risk of uneven distribution (circumferential density) of the metal wires 37a, contact with each other, or deformation of the outer semiconductive layer 36, and a decrease in shielding performance or an increase in eddy current. There is no problem of damaging the electrical characteristics, such as lowering the action of equalizing the electric field, and the bending radius of the cable of the propulsion coil can be made sufficiently small.
Further, when the metal wire is directly wound around the outer peripheral surface of the outer semiconductive layer 36, the press-winding tape 16 is required as shown in FIG. 6 of the conventional example, and the winding is complicated, but the metal wire 37a is attached to the sheath resin 38. In the case of embedding in, the press-wound tape becomes unnecessary and the manufacturing process is simplified.
When the metal shielding layer is made of a metal tape, the rigidity is increased and the flexibility of the cable is lowered. However, according to the wire shield around which the metal wire is wound, the flexibility can be avoided.
In addition, when the metal shielding layer is composed of a braid, a large eddy current is likely to be induced in the braid structure in which a conductive path in the cable circumferential direction is formed, which increases eddy current loss, but each metal wire is wound in a separated state. In the wire shield, a large eddy current is not induced and eddy current loss is small.

As the strand 32 constituting the above-described stranded conductor 33, as shown in FIG. 1 (c), the bare strand 32a is coated with a semiconductive material 32′b having a resistivity of 10 ⁻¹ to 10 ⁶ Ω · cm. Can also be applied. The semiconductive material is generally obtained by combining a polymer and conductive fine particles such as carbon black, silver, and copper, but a semiconductive material based on a low melting point resin, particularly a urethane resin, may be used.
In addition, as a definition of semiconductivity, the range of resistivity 10 ⁶ to 10 ⁹ Ω · cm may be called semiconductivity, but the range of resistivity 10 ⁻² to 10 ¹⁰ Ω · cm is semiconductivity. In this case, the resistivity range of 10 ⁻¹ to 10 ⁶ Ω · cm is also included in the semiconductive category. Even if the bare wire coating is not an insulating material, a semiconductive material having a resistivity in the range of 10 ⁻¹ to 10 ⁶ Ω · cm is effective for obtaining the effect of suppressing the eddy current as described above. This will be described below.
The resistance value of the semiconductive coating layer is not less than the resistance value that sufficiently prevents eddy currents between the strands, and does not cause a potential difference that causes a discharge between the stranded conductor and the internal semiconductive layer. Must be:
Here, a resistance value necessary for preventing an eddy current across the wires will be described.
Under the varying magnetic field conditions that the cable type propulsion coil receives, the eddy current loss of the conductor is proportional to the square of the magnetic flux multiplied by the frequency linked to the eddy current circuit and inversely proportional to the total resistance of the eddy current circuit. When the resistance value between two adjacent conductor wires is 0, it is synonymous with doubling the flux linkage, so the eddy current loss is 4 times the eddy current loss generated in one strand. Become. On the other hand, if a semiconductive layer is provided between two adjacent conductor wires and the total resistance of the eddy current circuit is quadrupled, the eddy current loss is reduced to ¼ and the eddy current loss generated in one strand. Can be equivalent. From the above, it is possible to simply obtain the resistance value necessary for preventing eddy currents across the strands by the following calculation.
R _a = ρ ₁ · L ₁ / S ₁ (1)
R _b = ρ ₁ · L ₁ / S ₁ + ρ ₂ · 2d / S ₂ (2)
R _a : Total resistance of eddy current circuit generated between two adjacent conductor wires (when there is no semiconductive layer)
R _b : Total resistance of eddy current circuit generated between two adjacent conductor wires (when there is a semiconductive layer)
ρ ₁ : resistivity of the strand conductor ρ ₂ : resistivity of the semiconductive layer L ₁ : length of the strand conductor portion of the eddy current circuit d: thickness of the strand covering semiconductive layer S ₁ : breakage of the strand conductor Area S ₂ : contact area of two adjacent conductor wires ÷ 2
From equation (1) and equation (2), ρ _{2 where} R _b = 4R _a is
ρ ₂ = 3ρ ₁ · L ₁ / S ₁ · S ₂ / 2d (3)
From the equation (3), when the resistivity of the semiconductive layer necessary to prevent eddy currents across the wires in the cable size shown in the embodiment is calculated, it is approximately 10 ⁻¹ Ω · cm.
On the other hand, the upper limit of the resistivity is preferably set to be equal to or lower than the resistivity of the internal semiconductive layer so as not to cause a potential difference that causes discharge between the stranded conductor and the internal semiconductive layer. It has been reported that the resistivity of the inner semiconductive layer is preferably 10 ⁶ Ω · cm or less so as not to cause corona discharge at the contact portion with the conductor. (GSEager, G. Barder and DASilver, “Corona detection experience in
commercial production of power cables with extruded insulation, “IEEE trans. Power
Apparatus and Systems, vol.PAS-88, pp.342-364, April 1969)

  In the ground coil device of the present invention, as shown in FIG. 2, it is preferable that the propulsion coil 23 is formed continuously with the connection cable portion 23a in terms of reducing the number of cable connection points, but independent propulsion as shown in FIG. The coils 1 may be connected by independent connection cables 3. Further, as shown in FIG. 5, a plurality of propulsion coils 6 may be formed continuously with one cable 8.

(A) is a cross-sectional view of a cable constituting the ground coil device of one embodiment of the present invention, (b) is an enlarged cross-sectional view of one strand constituting the stranded wire conductor in (a), and (c) is It is sectional drawing which shows the other Example (element wire which coat | covered the semiconductive material) of the strand. It is a schematic diagram explaining the arrangement | sequence of the propulsion coil by the ground coil apparatus of this invention. 1 is a schematic cross-sectional view of a magnetically levitated railway track to which the present invention is applied. It is a schematic diagram which shows the general arrangement | sequence of the propulsion coil in the magnetic levitation type railway track. It is a figure explaining the example which forms a propulsion coil with a cable. It is sectional drawing of the cable which comprises the conventional ground coil apparatus.

Explanation of symbols

21 Magnetically levitated railway track (guideway)
22 Guide Way Side Wall 23 Propulsion Coil 23a Connection Cable Portion 24 Guide / Left Coil 25 Car Body 26 Superconducting Coil 28 Connection Portion 29 Mounting Bracket 31 Cable 32 Constructing Ground Coil Device (Stranded Conductor) Wire 32a Bare Wire 32b Insulating material coating 32'b Semiconductive material coating 33 Wire 34 Internal semiconductive layer 35 Insulator 36 External semiconductive layer 37 Wire shield (metal shielding layer)
37a metal wire 38 sheath

Claims (8)

  A ground coil device installed on a magnetically levitated railway track, in which an inner semiconductive layer is formed in order from the inside around a stranded conductor formed by twisting a plurality of strands of a bare strand coated with an insulating material. A magnetic levitation railway ground coil device using a cable in which an insulating layer and an external semiconductive layer are formed, and a metal shielding layer and a sheath are formed around the insulating layer and the outer semiconductive layer. A ground coil device installed on a magnetic levitation railway track, which is formed by twisting together a plurality of strands of a bare strand covered with a semiconductive material having a resistivity of 10 ⁻¹ to 10 ⁶ Ω · cm. A magnetic levitation railway comprising a cable in which an inner semiconductive layer, an insulating layer, and an outer semiconductive layer are formed in order from the inside around a stranded wire conductor, and a metal shielding layer and a sheath are formed around the inner semiconductive layer. Ground coil device for use.   3. The magnetic levitation railway ground coil device according to claim 1, wherein the insulating material or semiconductive material of the element wire is a low melting point resin.   4. The magnetically levitated railway ground coil device according to claim 3, wherein the low melting point resin is a urethane resin.   5. The magnetically levitated railway ground coil device according to claim 1, wherein at least a part of the outermost strand in the stranded conductor is replaced with an uncovered bare strand.   6. The magnetic levitation railway ground coil device according to claim 1, wherein the insulating layer is an insulating layer made of a rubber-based insulating material.   7. The magnetic levitation system according to claim 1, wherein the metal shielding layer is a wire shield in which a plurality of metal wires are arranged in parallel and spirally on the outer periphery of the outer semiconductive layer at intervals. Railway ground coil equipment. 8. The magnetically levitated railway ground coil device according to claim 7, wherein the wire shield is embedded in a sheath made of resin.

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