Rotor of superconducting rotating electrical machine

Abstract

To provide a rotor of a superconducting rotating electric machine capable of shortening the shaft length with a simple configuration.SOLUTION: In a rotor of a superconducting rotating electrical machine according to an embodiment that uses a superconducting wire as a field winding, a rotor of a superconducting rotating electric machine having a plurality of current leads that are electrically connected to the field windings and spirally wound around the center of rotation.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] Embodiments of the present invention relate to a rotor of a superconducting rotating electrical machine.

Background Art

[0002] In recent years, so-called superconducting rotating electrical machines using superconducting conductors as field windings have been developed. In order to maintain superconductivity, the rotor of a superconducting rotating electrical machine using a superconducting wire such as a high-temperature superconducting wire (HTS) must be cooled below the critical temperature, and it is necessary to minimize the heat intrusion into the superconducting wire to maintain a low-temperature state during operation.

[0003] The heat intrusion is classified into radiative heat transfer, heat transfer by rarefied gas, conductive heat transfer, etc. Conventionally, in order to suppress these, the periphery of the cryogenic rotor is made into a vacuum layer with a low vacuum pressure, and members (such as torque tubes and current leads) that mechanically connect the low-temperature part and the normal-temperature part are cooled by the gas refrigerant vaporized in the cryogenic rotor. That is, the refrigerant vaporized in the cryogenic rotor is not simply discharged and recovered, but is effectively used as a medium for cooling these members in order to suppress the heat intrusion into the cryogenic rotor due to heat conduction of torque tubes, current leads, etc., and is recovered.

[0004] In the prior art, for example, a cryogenic refrigerant flows through a cooling path inside a current lead to cool the current lead. In order to suppress the heat intrusion into the low-temperature part through the current lead, it is common to consider the configuration of the cooling path, improve the heat exchange performance, increase the cooling length, and reduce the cross-sectional area of the current lead.

[0005] In recent years, superconducting rotating electrical machines using HTS that can obtain superconducting characteristics at about 30K have been developed, and refrigerants can be used not only liquid helium but also helium gas, liquid hydrogen, hydrogen gas, etc.

[0006] In addition, since a superconducting rotating electrical machine can generate a high magnetic field with a small coil, it can achieve a high output density and is expected to be utilized in various fields (such as ships, aircraft, trains, power generation fields, industrial fields, etc.).

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0008] In a superconducting rotating electrical machine using a superconducting wire as a field winding, a high output density is required. For example, in a type of current lead (direct cooling type) that directly flows a refrigerant inside the current lead for cooling, due to the requirements for refrigerant sealing performance, thermal insulation performance, low intrusion heat, and high heat exchange performance, the connection part requires a complex structure and it is necessary to use a thin and long conductive pipe, which becomes a factor in increasing the axial length of the rotor. Furthermore, when using a thin and long copper strip inside the rotating body, since the rigidity against the centrifugal force caused by rotation is low, a support structure is also required. In addition, a structure (such as a bellows, etc.) having a function to relieve the thermal stress generated by thermal contraction due to low temperature is required. Thus, when using a direct cooling type current lead, it leads to the complication of the structure and the enlargement of the size of the superconducting rotating electrical machine.

[0009] The problem to be solved by the present invention is to provide a rotor of a superconducting rotating electrical machine that can shorten the axial length with a simple configuration.

Means for Solving the Problems

[0010] According to an embodiment, in a rotor of a superconducting rotating electrical machine using a superconducting wire as a field winding, a plurality of current leads that are electrically connected to the field winding and wound in a helical shape around the rotation center Comprising , each of the plurality of current leads has one end Predeterminedelectrically connected to the field winding through a member and within the rotor Below the critical temperature is thermally conductively connected to a low-temperature part, and an insulating member having a thermal conductivity of a certain level or more is provided so as to be interposed between the Predetermined member and the low-temperature part. A rotor of a superconducting rotating electrical machine is provided.

Advantages of the Invention

[0011] According to the present invention, it is possible to provide a rotor of a superconducting rotating electrical machine that enables the axial length to be shortened with a simple configuration.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3A

Figure 3B

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0013] Hereinafter, embodiments will be described with reference to the drawings.

[0014] FIG. 1 is a configuration diagram showing an example of the configuration of a rotor of a superconducting rotating electrical machine according to an embodiment. FIG. 2 is a perspective view showing a part of the structure of the periphery of a helical current lead mounted on the rotor of the superconducting rotating electrical machine shown in FIG. 1.

[0015] What is shown in FIG. 1 is a rotor of a superconducting rotating electrical machine that uses a superconducting wire such as a high-temperature superconducting wire (HTS) as a field winding, and constitutes a superconducting rotating electrical machine together with a stator (not shown) arranged around it. In order to maintain superconductivity, the rotor of this superconducting rotating electrical machine includes a low-temperature part that is cooled below the critical temperature, and in order to maintain the low-temperature state during operation, it is configured so that the heat intrusion into the superconducting wire is minimized.

[0016] Specifically, as shown in FIG. 1, the rotor of the superconducting rotating electrical machine includes current leads 1, a low-temperature rotor 3, collectors 4A and 4B, field windings (superconducting wires) 5A and 5B, a torque tube 6, a normal-temperature damper 13, a vacuum insulation space 15, connection copper strips 16A and 16B, a refrigerant supply pipe 21, a refrigerant recovery pipe 22, a current lead support member 26, an indirect cooling helical groove 27, a low-temperature flange 28, flat cooling copper plates 29A and 29B, outlet copper strips 30A and 30B, center hole copper strips 31A and 31B, an insulating member 34, a low-temperature ring 38, current lead insertion members 41A and 41B, 42A and 42B, etc. Here, elements corresponding to the positive side of the direct current are assigned symbols with A appended, and elements corresponding to the negative side of the direct current are assigned symbols with B appended.

[0017] Between the low-temperature part and the normal-temperature part of this rotor, current leads 1 and a torque tube 6 that connect both in the vacuum insulation space 15 are provided. In particular, the current lead 1 of the present embodiment is composed of a plurality of current leads wound in a helical shape around the rotation center, and by forming a helical structure, it is possible to shorten the axial length of the rotor. Here, the case where there are two current leads 1 is illustrated, but it is not limited to this example, and a larger number than this example may be used.

[0018] The current lead 1 includes one current lead corresponding to the positive side of the direct current and one current lead corresponding to the negative side, and both are arranged to be separated from each other with a 180° shift in the circumferential direction of the rotor. By arranging them in such a 180°-shifted form, the imbalance of weight when the rotor rotates can be reduced as much as possible.

[0019] The current lead support member 26 is a cylindrical insulating member that supports each current lead so as to cover it from the surroundings, and prevents the current lead from being deformed or vibrating due to the centrifugal force when the rotor rotates. However, the current lead support member 26 is not necessarily required. Each current lead may be supported by other members.

[0020] One end of each of the plurality of current leads 1 is inserted into the conductive current lead insertion member 41A or 41B, and the other end is inserted into the conductive current lead insertion member 42A or 42B. The current lead insertion member 41A is attached to the flat cooling copper plate 29A or formed as a part of the flat cooling copper plate 29A, and the current lead insertion member 41B is attached to the flat cooling copper plate 29B or formed as a part of the flat cooling copper plate 29B.

[0021] The current lead 1 corresponding to the positive side of the direct current is electrically connected to the field winding 5A through the current lead insertion member 41A, the flat cooling copper plate 29A, and the outlet copper strip 30A at one end, and is thermally connected to the low-temperature part including the low-temperature flange 28 and the low-temperature ring 38 through the current lead insertion member 41A, the flat cooling copper plate 29A, and the insulating member 34. An insulating member 34 (for example, aluminum nitride having a high thermal conductivity) having a thermal conductivity of a certain level or more is provided between the flat cooling copper plate 29A and the low-temperature flange 28 so that the low-temperature flange 28 can cool the flat cooling copper plate 29A while maintaining the insulation between them. Further, at the other end of the current lead 1 corresponding to the positive side of the direct current, it is electrically connected to the collecting 4A through the current lead insertion member 42A, the center hole copper strip 31A, and the connection copper strip 16A. The field current is supplied to this collecting 4A through a brush.

[0022] Similarly, the current lead 1 corresponding to the negative side of the direct current is electrically connected to the field winding 5B through the current lead insertion member 41B, the flat cooling copper plate 29B, and the outlet copper strip 30B at one end, and is thermally connected to the low-temperature part including the low-temperature flange 28 and the low-temperature ring 38 through the current lead insertion member 41B, the flat cooling copper plate 29B, and the insulating member 34. An insulating member 34 (for example, aluminum nitride having a high thermal conductivity) having a thermal conductivity of a certain level or more is provided between the flat cooling copper plate 29B and the low-temperature flange 28 so that the low-temperature flange 28 can cool the flat cooling copper plate 29A while maintaining the insulation between them. Further, at the other end of the current lead 1 corresponding to the negative side of the direct current, it is electrically connected to the collecting 4B through the current lead insertion member 42B, the center hole copper strip 31B, and the connection copper strip 16B. The field current is supplied to this collecting 4B through a brush.

[0023] In the example of FIG. 1, in order to form the individual current leads 1 into a spiral structure, an example is shown in which the individual current leads 1 are wound two turns from the current lead insertion members 41A and 41B to the current lead insertion members 42A and 42B. However, the present invention is not limited to this example. The number of turns may be three or more. In addition, the number of turns may be 2.5 turns, 3.5 turns, or the like. In that case, for example, on the normal temperature section side, the arrangement positions of the members corresponding to the plus side of the direct current (current lead insertion members 42A, central hole copper strip 31A, connection copper strip 16A, collecting 4A) and the members corresponding to the minus side (current lead insertion members 42B, central hole copper strip 31B, connection copper strip 16B, collecting 4B) may be configured to be mutually interchanged.

[0024] The field winding 5A and 5B, which are superconducting wires, are incorporated in the low-temperature rotor 3. The low-temperature ring 38 is configured to indirectly cool the low-temperature rotor 3. For example, the low-temperature ring 38 has a flow path for flowing a refrigerant inside, and includes a spiral indirect cooling spiral groove 27 as a part of the flow path. The refrigerant is supplied into the low-temperature ring 38 through the refrigerant supply pipe 21 as shown by the arrow in FIG. 1. The refrigerant supplied into the low-temperature ring 38 is sent to the outer diameter side of the low-temperature ring 38, flows along the indirect cooling spiral groove 27 from the end of the low-temperature ring 38, indirectly cools the low-temperature rotor 3, and then heads toward the cooling copper plate 29 side. After further cooling the cooling copper plate 29, it is recovered through the refrigerant recovery pipe 22.

[0025] The current lead 1 having a spiral structure is made of, for example, a copper strip. From the following formula (1), based on the field current, the temperature on the normal temperature section side (high temperature end temperature), and the temperature on the low temperature section side (low temperature end temperature), the copper strip cross-sectional area and the copper strip length can be determined so that the amount of heat intrusion is minimized.

[0026] L / A=(λ / I√L o )cos -1 (T L / T H ) ···(1) Here, L: Copper strip length A: Copper strip cross-sectional area λ: Thermal conductivity I: Critical magnetic current L o : Lorentz number T L : Low - temperature end temperature T H : High - temperature end temperature Also, by adjusting the helical pitch, the axial length of the current lead 1 itself can be freely adjusted. Furthermore, since the thermal stress relaxation of the current lead 1 due to thermal contraction at low temperature can be obtained by the spring effect of the helical structure, the spring force can be adjusted by adjusting the cross - sectional area and the helical length.

[0027] Also, since the current lead 1 has a helical structure made of a copper strip, the hoop rigidity due to the annular structure is increased, making it more resistant to centrifugal force, and the rigidity can be adjusted by adjusting the cross - sectional area and the helical length.

[0028] As the material of the current lead 1, using phosphor - deoxidized copper with a low thermal conductivity among copper strips makes it easier to suppress the intrusion heat.

[0029] The end on the low - temperature part side of the current lead 1 is connected to flat - plate cooling copper plates 29A and 29B having a large area through current - lead insertion members 41A and 41B. Moreover, the flat - plate cooling copper plates 29A and 29B are attached to the low - temperature flange 28, for example, by bolt fastening through an insulating member 34 such as aluminum nitride with good thermal conductivity. Therefore, the cooling of the flat - plate cooling copper plates 29A and 29B by the low - temperature flange 28 cooled at the low - temperature part can be performed more efficiently, and the effect of suppressing the intrusion heat from the current lead 1 to the low - temperature rotor 3 can be enhanced.

[0030] Also, since the indirect - cooling helical groove 27 that forms the flow path of the refrigerant flowing inside the low - temperature ring 38 has a helical shape, the heat - transfer area is large, and the low - temperature rotor 3, the low - temperature flange 28, and thus the flat - plate cooling copper plates 29A and 29B can be cooled more efficiently.

[0031] For the electrical connection between the current lead 1 and the flat cooling copper plates 29A and 29B by the current lead insertion members 41A and 41B, for example, bolt fastening or EBW (Electron Beam Welding) may be applied. Thereby, the members are surely connected to each other. Further, in order to make the electrical connection more reliable, in each of the current lead insertion members 41A and 41B, a hole for casting solder is provided at the portion where one end of the current lead 1 is inserted, and a structure may be adopted in which the solder is cast from the hole to fix it. An example of the structure in that case is shown in FIGS. 3A and 3B.

[0032] FIG. 3A is a perspective view showing an example of a structure in which bolts are attached to the current lead insertion members 41A and 41B and holes 32 for casting solder are provided. FIG. 3B is a cross-sectional view showing an example of the cross-sectional shape of the current lead insertion member 41A shown in FIG. 3A taken along the arrow A-A.

[0033] As shown in FIG. 3A, bolts are attached to the current lead insertion members 41A and 41B, and holes 32 for casting solder are provided.

[0034] Further, as shown in FIG. 3B, the current lead insertion member 41A is provided with a stepped portion inside that meshes with the end of the current lead 1 to be inserted, and a bolt hole for passing the bolt 33 is provided. On the other hand, a thread for receiving the insertion of the bolt 33 is cut inside the current lead 1.

[0035] The bolt 33 is threaded through the bolt hole of the current lead insertion member 41A and into the inside of the current lead 1. When the bolt 33 is turned, the current lead 1 is pulled toward the stepped portion side of the current lead insertion member 41A and tightened. After performing bolt fastening in this way, solder is cast from the hole 32 for casting solder, and the solder is spread over the gap. When the solder solidifies, the electrical connection between the current lead 1, the current lead insertion member 41A, and the flat cooling copper plate 29A becomes reliable.

[0036] Depending on the spiral pitch and the number of spiral turns, the current lead 1 may have a large vibration because the rigidity in the direction perpendicular to the axis, which is characteristic of the coil spring, is low. To prevent this, it is desirable to support the current lead 1 using a support member having the same shape as the current lead support member 26 described above or other tape materials.

[0037] Figure 4 is a perspective view showing an example of a structure for supporting the current lead 1.

[0038] The current lead support members 35A and 35B shown in Figure 4 are two insulating members that form a cylindrical shape together and support the current lead 1 so as to cover it from the surroundings. For example, the current lead support member 35A is fixed to the flat plate-shaped cooling copper plate 29A side, and the current lead support member 35B is fixed to the flat plate-shaped cooling copper plate 29B side. The cylindrical current lead support members 35A and 35B have a plurality of concave depressions (for example, at the end and the center on the cooling copper plate side) for winding the tape material. By winding and tightening the insulating tape material 36 in the depressions, the current lead 1 is firmly supported by the cylindrical current lead support members 35A and 35B. By configuring in this way, the rigidity of the spiral current lead 1 can be increased, and the vibration suppression effect can be enhanced.

[0039] Instead of using the cylindrical current lead support members 35A and 35B and the tape material 36 as shown in Figure 4, the current lead 1 may be supported using the block-shaped current lead support member 37 and the tape material 36 as shown in Figure 5. In this case, the block-shaped current lead support member 37 is attached so as to be sandwiched between the current lead 1 corresponding to the plus of the direct current and the current lead 1 corresponding to the minus. By winding and tightening the insulating tape material 36 around the block-shaped current lead support member 37 and the current leads 1 on both sides, the current lead 1 is firmly supported. By configuring in this way as well, the rigidity of the spiral current lead 1 can be increased, and the vibration suppression effect can be enhanced.

[0040] In the above description, an example was given where there is only one pair of one current lead 1 corresponding to the positive side of the direct current and one current lead 1 corresponding to the negative side. However, it may be configured such that a plurality of pairs of one current lead 1 corresponding to the positive side of the direct current and one current lead 1 corresponding to the negative side are provided. That is, a plurality of current leads 1 corresponding to the positive side may be used to form a parallel circuit, and a plurality of current leads 1 corresponding to the negative side may also be used to form a parallel circuit. In that case, the individual current leads 1 are arranged in a helical shape while maintaining equal intervals in the circumferential direction of the rotor. When the number of parallel circuits is N, the pitch between adjacent current leads is 360 / N / 2 (degrees). By arranging in this way, it is possible to balance both the positive and negative sides with respect to rotation.

[0041] For example, when there are three pairs of one current lead 1 corresponding to the positive side and one current lead 1 corresponding to the negative side (when the number of parallel circuits is 3), as shown in FIG. 6, in addition to the current lead insertion members 41A and 41B described above, current lead insertion members 41C and 41D, and current lead insertion members 41E and 41F are arranged on the flat cooling copper plates 29A and 29B, and the current leads 1 extend from each of them in a helical shape while maintaining equal intervals in the circumferential direction of the rotor. In this case, the pitch between adjacent current leads is 60 degrees. The current leads 1 extending from each of the current lead insertion members 41A, 41C, and 41E on the flat cooling copper plate 29A side form a parallel circuit on the positive side, and the current leads 1 extending from each of the current lead insertion members 41B, 41D, and 41F on the flat cooling copper plate 29B side form a parallel circuit on the negative side.

[0042] By configuring in this way, it is possible to reduce the heat generation amount per current lead and disperse the heat, so that the effect of suppressing the heat intrusion into the cryogenic rotor 3 can be enhanced.

[0043] As described in detail above, according to the embodiment, it is possible to provide a rotor of a superconducting rotating electrical machine that enables shortening of the axial length with a simple configuration.

[0044] Although some embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention and are included in the invention described in the claims and its equivalent scope.

Explanation of Reference Numerals

[0045] 1... Current lead, 3... Low-temperature rotor, 4A, 4B... Collecting, 5A, 5B... Field winding (superconducting wire), 6... Torque tube, 13... Room-temperature damper, 15... Vacuum insulation space, 16A, 16B... Connecting copper strip, 21... Refrigerant supply pipe, 22... Refrigerant recovery pipe, 26... Current lead support member, 27... Indirect cooling spiral groove, 28... Low-temperature flange, 29A, 29B... Flat cooling copper plate, 30A, 30B... Outlet copper strip, 31A, 31B... Central hole copper strip, 32... Hole for casting solder, 33... Bolt, 34... Insulating member, 38... Low-temperature ring, 41A, 41B, 41C, 41D, 41E, 41F, 42A, 42B... Current lead insertion member.

Claims

1. In a rotor of a superconducting rotating electrical machine using a superconducting wire as a field winding, a plurality of current leads are provided which are electrically connected to the field winding and wound in a helical shape around the center of rotation, each of the plurality of current leads is electrically connected to the field winding through a predetermined member at one end and thermally conductively connected to a low-temperature part below the critical temperature in the rotor, an insulating member having a thermal conductivity of a certain level or more is provided so as to be interposed between the predetermined member and the low-temperature part, a rotor of a superconducting rotating electrical machine.

2. The predetermined member is a flat member. The rotor of the superconducting rotating electrical machine according to Claim 1.

3. The plurality of current leads include one current lead corresponding to the positive side of a direct current and one current lead corresponding to the negative side, and both are arranged in a shape shifted by 180° in the circumferential direction of the rotor. The rotor of the superconducting rotating electrical machine according to Claim 1.

4. A plurality of pairs of one current lead corresponding to the positive side and one current lead corresponding to the negative side are provided. The rotor of the superconducting rotating electrical machine according to Claim 3.

5. Individual current leads are arranged in a helical shape while maintaining equal intervals in the circumferential direction of the rotor. The rotor of the superconducting rotating electrical machine according to Claim 4.

6. In a rotor of a superconducting rotating electrical machine using a superconducting wire as a field winding, a plurality of current leads which are electrically connected to the field winding and wound in a helical shape around the center of rotation, and a cylindrical part composed of an insulating member for supporting so as to cover each current lead from the surroundings are provided. A rotor of a superconducting rotating electrical machine.

7. One current lead corresponding to the positive side, one current lead corresponding to the negative side, and a block-shaped current lead support member provided between these current leads are wound with an insulating tape. The rotor of the superconducting rotating electrical machine according to any one of Claims 3 to 5.

8. The flat member is further provided with a plurality of current lead insertion members to which one end of each of the plurality of current leads is inserted, each current lead insertion member is provided with a hole for casting solder at a portion where one end of the corresponding current lead is inserted. The rotor of the superconducting rotating electrical machine according to Claim 2.

9. Bolt fastening or EBW (Electron Beam Welding) is applied to the electrical connection between the individual current leads by the plurality of current lead insertion members and the flat member. The rotor of the superconducting rotating electric machine according to claim 8.

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