Superconducting Rotating Machine

Abstract

This superconducting rotating machine is provided with: a stator that has a cylindrical stator core and a stator winding wound toroidally around the stator core and formed from a superconducting material, the stator generating a rotating magnetic field; an inside rotor rotatably retained along the inner periphery of the stator; and an outside rotor rotatably retained along the outer periphery of the stator. The inside rotor and the outside rotor each have: at least one rotor winding selected from (a) a superconducting squirrel-cage winding having end rings and one or a plurality of rotor bars that are formed from a superconducting material, and (b) a normal-conducting squirrel-cage winding having end rings and one or a plurality of rotor bars that are formed from a normal-conducting material; and a rotor core provided with a plurality of slots for accommodating the rotor bars of the rotor winding(s).

Description

[Technical field]

[0001] The present invention relates to a superconducting rotating machine, and more particularly to a rotating electric machine including a plurality of rotors. [Background technology]

[0002] Rotating machines, which are electrical devices, are classified into DC machines and AC machines. Of these, AC machines generate AC power from mechanical power or generate mechanical power from AC power, and are mainly classified into induction machines and synchronous machines.

[0003] Induction machines, such as induction motors, rotate by generating induced torque in the rotor using a rotating magnetic field generated by applying an AC voltage to the stator winding. Induction motors are widely used because of their simple structure, low maintenance and low cost, but they have problems with efficiency and speed control.

[0004] A synchronous machine, such as a synchronous motor, rotates when a rotor equipped with electromagnets or permanent magnets is attracted to a rotating magnetic field generated by applying an AC voltage to a stator winding. Synchronous motors are efficient, but require additional equipment for starting and synchronous pull-in.

[0005] In recent years, a superconducting rotating machine that is capable of synchronous rotation despite having the configuration of an induction machine has been proposed (see Patent Document 1 below). For example, Patent Document 1 discloses a superconducting rotating machine that is capable of induced rotation and synchronous rotation, has good heat dissipation, and is easy to capture magnetic flux for synchronous rotation. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. WO2009 / 116219 Summary of the Invention [Problem to be solved by the invention]

[0007] As for rotating machines using superconducting materials, in addition to those using superconducting materials in the rotor, those using superconducting materials in the stator are also envisioned. It is expected that a rotating machine using superconducting materials in the stator will further improve the efficiency of energy conversion from electric power to torque.

[0008] Meanwhile, in recent years, the applications of rotating machines have been expanding year by year, and there is a strong demand for the development of rotating machines with high output (torque). For example, in order to produce high torque in a rotating machine using a superconducting material for the stator, one method is to increase the critical current in the stator core (the maximum current value that can formally maintain zero resistance in a superconducting state). In order to increase the critical current in the stator core, for example, a stator with a toroidal structure (hereinafter, a stator with a toroidal structure may be simply referred to as a "toroidal stator"). In this regard, in conventional induction motors using normal conductive materials, the use of a toroidal stator was considered to be disadvantageous in terms of energy conversion efficiency, but in motors using superconductivity for the stator, the effect of improving the critical current in the core often outweighs the disadvantages of energy conversion efficiency.

[0009] However, due to its structure, the toroidal stator has a large leakage flux not only inward in the radial direction but also outward. Since the leakage flux does not contribute to torque, it is known to be a cause of a decrease in the efficiency of energy conversion from power to torque and to affect peripheral equipment. Therefore, in order to prevent the effects on peripheral equipment, it is necessary to install a means for preventing leakage flux, such as a magnetic shield, on the outside of the toroidal stator.

[0010] SUMMARY OF THE PRESENT EMBODIMENT In order to solve the above problems, an object of the present invention is to provide a superconducting rotating machine having excellent energy conversion efficiency. [Means for solving the problem]

[0011] The present invention provides a superconducting rotating machine comprising: a stator having a cylindrical stator core and a stator winding formed of a superconducting material and wound toroidally around the stator core, generating a rotating magnetic field; an inner rotor rotatably held on the inner peripheral side of the stator; and an outer rotor rotatably held on the outer peripheral side of the stator, wherein the inner rotor and the outer rotor each have at least one rotor winding selected from a superconducting squirrel-cage winding (a) having a rotor bar and end rings formed of one or more superconducting material and a normal conducting squirrel-cage winding (b) having a rotor bar and end rings formed of one or more normal conducting material; and a rotor core having a plurality of slots to accommodate each rotor bar of the rotor winding.

[0012] According to the superconducting rotating machine of the present invention, a toroidal stator is used, which is wound in a toroidal shape around a cylindrical stator core and has a superconducting material as a stator winding, and therefore the critical current in the core is high. In addition, since an outer rotor is rotatably held on the outer periphery of the stator, leakage flux to the outside in the radial direction of the stator can be used as the output (torque) of the rotating machine. Therefore, the superconducting rotating machine of the present invention has excellent energy conversion efficiency and can further increase the output (torque).

[0013] Furthermore, according to the superconducting rotating machine of the present invention, the outer rotor serves as a magnetic shield to prevent leakage magnetic flux, so that the influence of leakage magnetic flux on peripheral devices can be suppressed.

[0014] Furthermore, one aspect of the present invention provides a superconducting rotating machine, wherein at least one of the inner rotor and the outer rotor has at least a superconducting squirrel-cage winding (a) as the rotor winding.

[0015] According to this aspect, a superconducting squirrel-cage winding (a) is used in at least one of the inner rotor and the outer rotor, so that the rotor using the superconducting squirrel-cage winding (a) captures magnetic flux in a superconducting state, thereby enabling synchronous rotation.

[0016] Furthermore, as one aspect of the present invention, there is provided a superconducting rotating machine, wherein at least one of the inner rotor and the outer rotor has a superconducting squirrel-cage winding (a) and a normal conducting squirrel-cage winding (b) as the rotor winding.

[0017] According to this aspect, since both the superconducting squirrel-cage winding (a) and the normal conducting squirrel-cage winding (b) are used as the rotor windings in at least one of the inner rotor and the outer rotor, the rotor using the superconducting squirrel-cage winding (a) and the normal conducting squirrel-cage winding (b) can switch between slip rotation and synchronous rotation.

[0018] Furthermore, as one aspect of the present invention, there is provided a superconducting rotating machine, wherein the inner rotor and the outer rotor have at least a superconducting squirrel-cage winding (a) as the rotor winding.

[0019] According to this aspect, since the superconducting squirrel-cage winding (a) is used in both the inner rotor and the outer rotor, synchronous rotation is possible by capturing magnetic flux in a superconducting state of both the inner rotor and the outer rotor.

[0020] Furthermore, as an aspect of the present invention, there is provided a superconducting rotating machine, in which the inner rotor and the outer rotor have at least a superconducting squirrel-cage winding (a) as the rotor windings, and a critical current (A1) for putting the superconducting squirrel-cage winding (a-1) of the inner rotor into a flux flow state is different from a critical current (A2) for putting the superconducting squirrel-cage winding (a-2) of the outer rotor into a flux flow state.

[0021] According to this aspect, the inner rotor and the outer rotor have at least a superconducting squirrel-cage winding (a) as the rotor winding, and the critical current (A1) of the inner rotor and the critical current (A2) of the outer rotor are different, so that the timing at which magnetic flux is captured in the superconducting state can be made different for the inner rotor and the outer rotor.

[0022] Furthermore, as an aspect of the present invention, there is provided a superconducting rotating machine, in which the inner rotor and the outer rotor have at least a superconducting squirrel-cage winding (a) as the rotor winding, and only the superconducting squirrel-cage winding (a) of either the inner rotor or the outer rotor can be switched to a magnetic flux flow state.

[0023] According to this aspect, it is possible to switch between putting only one of the superconducting squirrel-cage windings (a) of the inner rotor or the outer rotor into a flux flow state, or putting both rotors into a flux flow state. Therefore, for example, by configuring it so that only one of the superconducting squirrel-cage windings (a) of the inner rotor or the outer rotor can be in a flux flow state at the time of low load, Joule loss can be reduced even at the time of low load, and the rotors can rotate with high efficiency.

[0024] Furthermore, as an aspect of the present invention, there is provided a superconducting rotating machine in which a critical current (A1) for putting the superconducting squirrel-cage winding (a-1) of the inner rotor into a flux flow state and a critical current (A2) for putting the superconducting squirrel-cage winding (a-2) of the outer rotor into a flux flow state are different, and only one of the superconducting squirrel-cage windings (a) of the inner rotor or the outer rotor can be switched into the flux flow state depending on the difference between the critical current (A1) and the critical current (A2).

[0025] According to this aspect, since there is a difference between the critical current (A1) and the critical current (A2), an induced current that captures magnetic flux can be passed only through the superconducting squirrel-cage winding (a) having a low critical current in a synchronous rotation state during low load (low current). This makes it possible to autonomously switch between a mode in which only the superconducting squirrel-cage winding (a) of either the inner rotor or the outer rotor is allowed to enter a magnetic flux flow state and a mode in which both rotors are allowed to enter a magnetic flux flow state according to the load (rotation speed) without providing a physical switch or the like. Effect of the Invention

[0026] According to the present invention, it is possible to provide a superconducting rotating machine having excellent energy conversion efficiency. [Brief description of the drawings]

[0027] [Figure 1] FIG. 2 is a schematic diagram for explaining the magnetic mirror image effect in a toroidal stator. [Diagram 2] 1 is an explanatory diagram showing an example of an axial cross section and a radial cross section of a superconducting rotating machine; [Diagram 3] FIG. 2 is an explanatory diagram showing an example of the configuration of a toroidal stator. [Figure 4] FIG. 2 is an explanatory diagram illustrating an example of a configuration of a rotor. [Diagram 5] FIG. 1 is a diagram showing magnetic flux lines (FEM analysis results) when current is applied to a superconducting rotating machine. [Figure 6] 1 is a graph showing the relationship between torque and slip during slip rotation in a normal conducting state and during slip or synchronous rotation in a superconducting state. [Figure 7] 1A and 1B are schematic diagrams for explaining a shielded state, a magnetic flux flow state, and a magnetic flux capture state. [Figure 8] 1 is a graph showing the results of output (torque / Nm) versus drive time for a number of superconducting rotating machines. [Figure 9] FIG. 13 is an explanatory diagram showing an axial cross section of another example of a superconducting rotating machine. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] The superconducting rotating machine of the present invention uses a toroidal stator made of superconducting material, and can increase the critical current in the stator core. The reason why the critical current in the stator core is increased by using a toroidal stator will be explained below with reference to Fig. 1. Fig. 1 is a schematic diagram for explaining the magnetic mirror effect in a toroidal stator, where Fig. 1(A) shows a normal winding method and Fig. 1(B) shows a toroidal winding method.

[0029] As shown in Figure 1(A), when a current is passed through a superconducting material 1A (conductor) placed between two magnetic bodies 2 from the front to the back of the page, a magnetic field is generated around the conductor 1A in the direction indicated by the arrow in the figure due to the right-hand screw rule. At this time, a magnetic mirror image 3A indicated by a dashed line is generated within each magnetic body 2. In relation to the magnetic field generated by this magnetic mirror image 3A, the magnetic fields in the space 4 in which the superconducting material 2A exists reinforce each other in the magnetic flux direction parallel to the magnetic bodies 2 (parallel to the direction indicated by the arrow X in Figure 1) and weaken each other in the perpendicular direction (direction indicated by the arrow Y in Figure 1) due to the magnetic mirror effect. Furthermore, when a rectangular superconducting material with a high aspect ratio of the cross-sectional shape is used, the critical current decreases as the component (perpendicular magnetic field) applied perpendicular to the wide cross-sectional surface of the magnetic field vector applied to the superconducting material increases. For this reason, for example, as in the conventional winding method shown in Fig. 1(A), when the long side (wide cross-sectional surface) of the superconducting material 1A is arranged parallel to the depth direction of the magnetic body 2 (parallel to the direction indicated by the arrow Y in Fig. 1), the direction in which the magnetic field strengthens coincides with the direction in which the critical current of the superconducting material weakens, and the magnetic flux component (parallel magnetic flux component) indicated by the thick arrow around the superconducting material 1A significantly reduces the critical current. In this case, the magnetic flux component indicated by the thin arrow in Fig. 1(A) also reduces the critical current, but to a small extent. In other words, when the long side (wide side of the cross section) of the superconducting material 1A is arranged parallel to the depth direction of the magnetic body 2 (parallel to the direction indicated by the arrow Y in FIG. 1) as shown in FIG. 1(A), the parallel magnetic field component strengthened by the magnetic mirror effect coincides with the direction in which the critical current of the superconducting material weakens, resulting in a significant decrease in the critical current.

[0030] In contrast, as shown in FIG. 1(B), when the long side (cross-sectional wide surface side) of the rectangular superconducting material 1B with a high aspect ratio in cross-sectional shape is arranged in a direction perpendicular to the depth direction of the magnetic body 2 (parallel to the direction indicated by the arrow X in FIG. 1), the critical current of the superconducting material 1B is significantly reduced by the perpendicular magnetic field component indicated by the thin arrow in FIG. 1(B), but is not so reduced by the parallel magnetic field component indicated by the thick arrow in FIG. 1(B). In other words, in FIG. 1(B), the perpendicular magnetic field component weakened by the magnetic mirror effect coincides with the direction in which the critical current of the superconducting material weakens (perpendicular to the wide surface), so that the critical current in the magnetic body (iron core) can be improved compared to FIG. 1(A). In this specification, the relationship between "perpendicular" and "parallel" is a concept that includes the relationships of approximately perpendicular and approximately parallel.

[0031] Generally, most superconducting materials are highly brittle and have low flexibility. Furthermore, among superconducting materials, most superconducting wires have a rectangular cross-sectional shape with a high aspect ratio. For this reason, when a stator is manufactured using a superconducting material with a rectangular cross-sectional shape, the superconducting material is often used in a configuration that can be bent in a direction perpendicular to the long side in order to wind it around the stator core. In this way, in order to increase the critical current in the stator core by using a superconducting material with a rectangular cross-sectional shape and utilizing the magnetic mirror effect as described above, it is preferable to install the superconducting material in a slot or groove of the stator core so that the long side (wide side of the cross-section) of the cross-sectional shape (rectangle) is perpendicular to the radial direction (depth direction) of the stator. In this case, the direction in which the superconducting material with a rectangular cross-sectional shape can be wound is the radial direction of the stator (i.e., the direction perpendicular to the long side of the cross-section of the superconducting material). For this reason, when a superconducting material is placed in a slot or groove of a stator core so that the long side (wide side) of the cross-sectional shape (rectangle) is perpendicular to the radial direction (depth direction) of the stator, the material is wound in a toroidal shape in order to wind the material around the stator. Thus, by winding the superconducting material in a toroidal shape around the stator core, the critical current in the stator core can be increased. However, the relationship between the long side (wide side) of the cross-sectional shape (rectangle) of the superconducting material and the radial direction (depth direction) of the stator may be such that the long side of the slot itself is slightly inclined (for example, circumferentially) with respect to the radial direction of the stator, as long as the relative spatial arrangement between the space inside the (vertical) slot and the superconducting material is maintained.

[0032] In the present invention, the superconducting material used in the stator is not limited to a material having a rectangular cross section, and for example, a bulk material having a low aspect ratio of the cross section, i.e., a substantially circular or substantially square, can be used. Even when such a material is used, by aligning the c-axis direction of the crystal structure of the superconducting material with the direction of the magnetic field generated by the right-handed helical rule as shown in Fig. 1(B), it is possible to suppress the decrease in the critical current of the superconducting material due to the magnetic flux component parallel to the radial direction of the stator core (i.e., the above-mentioned vertical magnetic field component), and therefore to increase the critical current in the stator core.

[0033] A preferred embodiment of the present invention will now be described with reference to the drawings. FIG. 2 is an explanatory diagram showing an example of an axial cross section (see FIG. 2(A)) and a radial cross section (see FIG. 2(B)) of superconducting rotating machine 100 of the present embodiment. As shown in FIG. 2, superconducting rotating machine 100 includes a toroidal stator 12 having a stator winding formed of a superconducting wire and wound in a toroidal shape around a cylindrical stator core, which generates a rotating magnetic field, an inner rotor 20 rotatably held on the inner periphery side of toroidal stator 12, and an outer rotor 30 rotatably held on the outer periphery side of toroidal stator 12. Toroidal stator 12, inner rotor 20, and outer rotor 30 are housed in a cylindrical case 50. As described below, in superconducting rotating machine 100 of the present embodiment, inner rotor 20 and outer rotor 30 rotate by passing a three-phase current through toroidal stator 12, and a high torque output can be obtained while having excellent energy conversion efficiency.

[0034] (Toroidal stator) Fig. 3 is an explanatory diagram showing an example of the configuration of the toroidal stator 12. As shown in Fig. 3, the toroidal stator 12 has a cylindrical stator core 14 and a stator winding 16 formed of a superconducting wire and wound in a toroidal shape around the stator core 14. By passing a three-phase current through the stator winding 16, a rotating magnetic field is generated.

[0035] The stator core 14 is a cylindrical member having a radial cross section in the shape of a ring. The stator core 14 may be a member in which electromagnetic steel sheets, such as silicon steel sheets, are stacked in the axial direction. The stator core 14 is provided with slots (not shown), and the stator windings 16 are housed in the slots. As shown in FIG. 2, the stator core 14 is fixed to the inner wall of the case 50 of the superconducting rotating machine 100 via joints 14A. Although a stator having slots is used in this embodiment, the present invention is not limited to this embodiment, and a stator provided with open slots or grooves instead of slots may also be used.

[0036] The stator winding 16 is made by bundling a plurality of superconducting wires (bismuth-based high-temperature superconducting wires in this embodiment), and each wire has a rectangular cross-sectional shape (however, the cross-section is not limited to this). Although not shown, the plurality of superconducting wires stacked in the radial direction of the stator are arranged so that the long side (cross-sectional wide side) of the rectangular cross section of each wire perpendicularly intersects with the radial direction of the stator. The superconducting wire is made by covering a plurality of bismuth-based high-temperature superconducting filaments with a highly conductive metal such as copper, aluminum, silver, or gold. From the viewpoint of ease of starting the superconducting rotating machine 100, it is preferable to use a superconducting wire having a higher critical temperature than at least one of the superconducting wires used in the superconducting squirrel-cage windings 22A and 32A as the superconducting wire used in the stator winding 16 of the toroidal stator 12. The reason for this will be described later.

[0037] As described above, the stator winding 16 is inserted into the slots on the surface of the stator core 14 and wound around the stator core 14 in a toroidal shape to function as a coil. In this embodiment, 24 slots are provided on the inner and outer peripheral surfaces of the stator core 14, respectively, so as to be arranged at equal intervals in the circumferential direction. In addition, each slot is formed so as to be continuous across the inner and outer peripheral surfaces of the stator core. Throughout this specification, the term "outside" of the stator simply refers to the outer peripheral surface side of the stator, and the term "inside" of the stator simply refers to the inner peripheral surface side of the stator. In addition, as shown in FIG. 3, the stator winding 16 is arranged (wound) counterclockwise along the circumferential direction of the stator core 14 so as to generate a rotating magnetic field in the order of the stator windings 16U, 16V, and 16W.

[0038] In this embodiment, the stator windings 16 are three-phase windings that are individually connected. The superconducting rotating machine 100 is a three-phase motor, and each stator winding 16 is assigned to any one of a U-phase coil, a V-phase coil, and a W-phase coil. That is, 24 superconducting coils are arranged on the stator core 14. In other words, eight U-phase superconducting coils (stator windings 16U), eight V-phase superconducting coils (stator windings 16V), and eight W-phase superconducting coils (stator windings 16W) are arranged on the stator core 14. The eight U-phase superconducting coils are electrically connected in series, the eight V-phase superconducting coils are electrically connected in series, and the eight W-phase superconducting coils are electrically connected in series. The stator windings 16 may be connected in series or in parallel.

[0039] The method of connection of each stator winding 16 is not particularly limited, and may be star connection, delta connection, or the like. The stator winding 16 may be wound around the stator core 14 in a concentrated winding or distributed winding manner. In this embodiment, a rotating magnetic field with four poles is formed in the stator core 14 by passing a three-phase current through the stator winding 16. In this embodiment, the number of turns per pole per phase of the stator winding 16 is 12.

[0040] (Rotor) Fig. 4 is an explanatory diagram showing an example of a rotor configuration. Specifically, Fig. 4(A) shows a rotor core, Fig. 4(B) shows a superconducting squirrel-cage winding (a), and Fig. 4(C) shows a normal-conducting squirrel-cage winding (b).

[0041] First, as shown in Fig. 2, superconducting rotating machine 100 of the present embodiment includes inner rotor 20 rotatably held on the inner periphery side of toroidal stator 12, and outer rotor 30 rotatably held on the outer periphery side. As shown in Fig. 2(A), in this embodiment, inner rotor 20 and outer rotor 30 are connected to each other at their rotor cores via connecting part 20A, and inner rotor 20 and outer rotor 30 are configured to rotate as a unit.

[0042] 2(B) and 4, inner rotor 20 includes superconducting squirrel-cage winding 22A and normal conductive squirrel-cage winding 22B, and inner rotor core 24. Similarly, outer rotor 30 includes superconducting squirrel-cage winding 32A and normal conductive squirrel-cage winding 32B, and outer rotor core 34. As described above, inner rotor core 24 and outer rotor core 34 are connected via connecting part 20A and configured as an integral unit.

[0043] -Inner rotor- As shown in FIG. 2, inner rotor 20 is arranged at a predetermined interval on the inner periphery side of toroidal stator 12. Next, as shown in FIG. 4(A), inner rotor core 24 of inner rotor 20 is cylindrical and has a plurality of slots 24S on its outer periphery side for accommodating each rotor bar of the rotor winding. Furthermore, inner rotor 20 has a rotating shaft 40 coaxially attached to inner rotor core 24. Furthermore, inner rotor 20 has superconducting squirrel-cage winding 22A having rotor bar 26A and end ring 28A formed of superconducting wire, and normal conducting squirrel-cage winding 22B having rotor bar 26B and end ring 28B formed of normal conducting wire, as shown in FIGS. 4(B) and (C). Note that in this embodiment, an inner rotor having slots is used, but the present invention is not limited to this aspect, and an inner rotor provided with open slots or grooves instead of slots can also be used.

[0044] Inner rotor core 24 may be formed by stacking electromagnetic steel sheets, such as silicon steel sheets, in the axial direction. As shown in FIG. 4(A), inner rotor core 24 has a central portion formed with rotating shaft receiving hole 28 for receiving rotating shaft 40. As described above, inner rotor core 24 has a plurality of slots 24S formed near its outer periphery, penetrating in the axial direction, at predetermined intervals in the circumferential direction. In this embodiment, slots 24S are formed obliquely with respect to the axial direction of inner rotor core 24, and have an oblique slot (skew) configuration. However, the present invention is not limited to this aspect, and for example, slots 24S may be parallel to the axial direction of inner rotor core 24 (the angle between the axial direction of inner rotor core 24 and slots 24S is 0°).

[0045] 4(B), superconducting squirrel-cage winding 22A is composed of a plurality of rotor bars 26A and a pair of annular end rings 28A that short-circuit both ends of each rotor bar 26A. A plurality of rotor bars 26A are housed in slots 24S of inner rotor core 24.

[0046] Rotor bar 26A is made by bundling a plurality of superconducting wires (bismuth-based high-temperature superconducting wires in this embodiment) and has a rectangular cross section (however, not limited to a rectangular cross section). The superconducting wire can be made, for example, by covering a plurality of bismuth-based high-temperature superconducting filaments with a highly conductive metal such as copper, aluminum, silver, or gold. The number of rotor bars 26A is the same as the number of slots 24S of inner rotor core 24. That is, in this embodiment, the number of rotor bars 26A and the number of slots 24S are each 24.

[0047] Rotor bars 26A are arranged at predetermined intervals in the circumferential direction and obliquely with respect to the axial direction of the cage to form a cylindrical cage with a skewed structure. However, the present invention is not limited to this embodiment, and superconducting cage winding 22A may be configured, for example, such that rotor bars 26A are parallel to the axial direction of inner rotor core 24 (the angle between the axial direction of inner rotor core 24 and rotor bars 26A is 0°). Rotor bar 26A is formed to be longer than the axial length of inner rotor core 24, and is configured to protrude from slot 24S when accommodated in slot 24S. Similarly to rotor bar 26A, end ring 28A is constructed using a superconducting wire such as a bismuth-based high-temperature superconducting wire. Ends of rotor bar 26A protruding from slot 24S are joined to the pair of end rings 28A, respectively.

[0048] 4(C), normal conducting squirrel-cage winding 22B is composed of a plurality of rotor bars 26B and a pair of annular end rings 28B that short-circuit both ends of each rotor bar 26B. Rotor bars 26B are housed in slots 24S of inner rotor core 24.

[0049] Rotor bars 26B are made of a highly conductive material such as copper, aluminum, silver, or gold, and have a rectangular cross section (however, the cross section is not limited to a rectangular cross section). The number of rotor bars 26B is the same as the number of slots 24S of inner rotor core 24. That is, in this embodiment, the number of rotor bars 26B is 24. Rotor bars 26B are arranged at predetermined intervals in the circumferential direction and obliquely with respect to the axial direction of the cage so as to form a cylindrical cage larger than superconducting cage winding 22A and having a skewed structure. However, the present invention is not limited to this embodiment, and for example, superconducting cage winding 22A may be configured so that rotor bars 26B are parallel to the axial direction of inner rotor core 24 (the angle between the axial direction of inner rotor core 24 and rotor bars 26B is 0°).

[0050] Rotor bar 26B is formed to be longer than the axial length of inner rotor core 24 and is configured to protrude from slot 24S when accommodated in slot 24S. Rotor bar 26B is inserted within slot 24S, and outside rotor bar 26A of superconducting squirrel-cage winding 22A. That is, in inner rotor 20, rotor bar 26A made of superconducting wire is arranged on the inside (center side) within slot 24S, and rotor bar 26B made of normal conducting wire is arranged on the outside (outer periphery side).

[0051] Like rotor bar 26B, end ring 28B is made of a highly conductive material such as copper, aluminum, silver, gold, etc. Ends of rotor bar 26B protruding from slot 24S are joined to the pair of end rings 28B, respectively.

[0052] Rotating shaft 40 is inserted into and attached to rotating shaft receiving hole 28 of inner rotor core 24. Rotating shaft 40 is rotatably supported within case 50 via bearings 42, such as bearings.

[0053] -Outer rotor- As shown in Fig. 2, outer rotor 30 is arranged on the outer periphery of toroidal stator 12 with a predetermined interval therebetween. Also, as shown in Fig. 4(A), outer rotor core 34 of outer rotor 30 is cylindrical and has a plurality of slots 34S on its inner periphery for accommodating each rotor bar of the rotor winding. Also, outer rotor 30 has superconducting squirrel-cage winding 32A having rotor bar 36A and end ring 38A formed of superconducting wire, and normal conducting squirrel-cage winding 32B having rotor bar 36B and end ring 38B formed of normal conducting wire, as shown in Figs. 4(B) and (C). Note that superconducting squirrel-cage winding 32A has substantially the same configuration as normal conducting squirrel-cage winding 22B of inner rotor 20, except for the size and material. Similarly, except for the size and material, normal conducting squirrel-cage winding 32B has substantially the same configuration as superconducting squirrel-cage winding 22A of inner rotor 20. For this reason, for superconducting squirrel-cage winding 32A and normal conducting squirrel-cage winding 32B, corresponding reference numbers are given in parentheses in Figures 4(B) and (C).

[0054] Outer rotor core 34 may be formed by laminating electromagnetic steel sheets, such as silicon steel sheets, in the axial direction. As described above, a plurality of slots 34S penetrating in the axial direction are formed at predetermined intervals in the circumferential direction near the inner circumference of outer rotor core 34. Slots 34S are formed obliquely with respect to the axial direction of outer rotor core 34, and have an oblique slot (skew) configuration. As shown in FIG. 2, outer rotor core 34 and inner rotor core 24 are connected at one end via connecting part 20A. However, the present invention is not limited to this aspect, and for example, slots 34S may be parallel to the axial direction of outer rotor core 34 (the angle between the axial direction of outer rotor core 34 and slots 34S is 0°). Although the outer rotor provided with slots is used in this embodiment, the present invention is not limited to this aspect, and an outer rotor provided with open slots or grooves instead of slots may also be used.

[0055] As shown in FIG. 4C, the superconducting cage winding 32A is composed of a plurality of rotor bars 36A and a pair of annular end rings 38A that short-circuit both ends of each rotor bar 36A. The plurality of rotor bars 36A are accommodated in slots 34S of the outer rotor core 34.

[0056] The rotor bar 36A is formed by bundling a plurality of superconducting wires (bismuth-based high-temperature superconducting wires in this embodiment) and has a rectangular cross section (however, the cross section is not limited to a rectangular cross section). The superconducting wire can be formed, for example, by covering a plurality of bismuth-based high-temperature superconducting filaments with a highly conductive metal such as copper, aluminum, silver, or gold. The number of rotor bars 36A is the same as the number of slots 34S of the outer rotor core 34. That is, in this embodiment, the number of rotor bars 36A and the number of slots 34S are each 24.

[0057] Rotor bars 36A are arranged at predetermined intervals in the circumferential direction and obliquely with respect to the axial direction of the cage to form a cylindrical cage with a skewed structure. However, the invention is not limited to this embodiment, and superconducting cage winding 32A may be configured, for example, so that rotor bars 36A are parallel to the axial direction of outer rotor core 34 (the angle between the axial direction of outer rotor core 34 and rotor bars 36A is 0°). Rotor bar 36A is formed to be longer in the axial direction than outer rotor core 34, and is configured to protrude from slot 34S when accommodated in slot 34S. Similarly to rotor bar 36A, end ring 38A is constructed using a superconducting wire such as a bismuth-based high-temperature superconducting wire. Ends of rotor bar 36A protruding from slot 34S are joined to the pair of end rings 38A, respectively.

[0058] 4(B), normal conducting squirrel-cage winding 32B is composed of a plurality of rotor bars 36B and a pair of annular end rings 38B that short-circuit both ends of each rotor bar 36B. Rotor bars 36B are housed in slots 34S of outer rotor core 34.

[0059] Rotor bars 36B are made of a highly conductive material such as copper, aluminum, silver, or gold, and have a rectangular cross section (however, the cross section is not limited to a rectangular cross section). The number of rotor bars 36B is the same as the number of slots 34S of outer rotor core 34. That is, in this embodiment, the number of rotor bars 36B is 24. Rotor bars 36B are arranged at a predetermined interval in the circumferential direction and obliquely with respect to the axial direction of the cage so as to form a cylindrical cage smaller than superconducting cage winding 32A and having a skewed structure. However, the present invention is not limited to this embodiment, and for example, superconducting cage winding 32A may be configured so that rotor bars 36B are parallel to the axial direction of outer rotor core 34 (the angle between the axial direction of outer rotor core 34 and rotor bars 36B is 0°).

[0060] Rotor bar 36B is formed to be longer than the axial length of outer rotor core 34 and is configured to protrude from slot 34S when accommodated in slot 34S. Rotor bar 36B is inserted within slot 34S, and inside rotor bar 36A of superconducting squirrel-cage winding 32A. That is, in outer rotor 30, rotor bar 36B made of normal conducting wire is arranged on the inside (center side) within slot 34S, and rotor bar 36A made of superconducting wire is arranged on the outside (outer periphery) thereof.

[0061] Like the rotor bar 36B, the end ring 38B is made of a highly conductive material such as copper, aluminum, silver, gold, etc. Each end of the rotor bar 36B protruding from the slot 34S is joined to the pair of end rings 38B, respectively.

[0062] According to the superconducting rotating machine 100 configured as described above, when the rotating machine is driven, first, the stator winding 16 of the toroidal stator 12, which is configured using at least superconducting wires, is cooled to put it into a superconducting state. At this time, it is preferable that the superconducting squirrel-cage winding 22A of the inner rotor 20 and the superconducting squirrel-cage winding 32A of the outer rotor 30 are cooled at the same time. Next, when a three-phase AC is applied to the superconducting rotating machine 100, a current flows through the stator winding 16 of the toroidal stator 12, and a rotating magnetic field is generated in the stator core 14. At this time, since the toroidal stator 12 is used in this embodiment, the rotating magnetic field is generated not only on the inner circumference side but also on the outer circumference side of the toroidal stator 12.

[0063] 5 is a diagram showing magnetic flux lines (FEM analysis results) when a current is applied to the superconducting rotating machine. As shown in FIG. 5, when a three-phase AC is applied to the superconducting rotating machine 100 of this embodiment, it can be seen that magnetic flux lines are generated on both the inner and outer circumferential sides of the toroidal stator 12.

[0064] When the superconducting squirrel-cage windings 22A and 32A are in a normal conducting state (non-superconducting state), an induced current flows in the normal conducting squirrel-cage windings 22B and 32B due to the rotating magnetic field generated by the toroidal stator 12, generating an induced (slip) torque. At this time, the superconducting rotating machine 100 rotates primarily due to the induced (slip) torque, and each rotor exhibits a torque characteristic corresponding to "slip rotation (normal conducting state)" shown in Fig. 6. Fig. 6 is a graph showing the relationship between torque and slip during slip rotation in the normal conducting state and during slip or synchronous rotation in the superconducting state.

[0065] When the superconducting rotating machine 100 is in a slip rotation state, a small amount of induced current also flows through the superconducting squirrel-cage windings 22A and 32A. However, since the induced current flowing through the normal conductive squirrel-cage winding 22B is much larger, the induced (slip) torque generated in the normal conductive squirrel-cage windings 22B and 32B becomes dominant over the induced (slip) torque generated in the superconducting squirrel-cage windings 22A and 32A.

[0066] On the other hand, in the superconducting rotating machine 100, when the superconducting squirrel-cage windings 22A and 32A change from a normal conducting state to a superconducting state, the superconducting squirrel-cage windings 22A and 32A capture the magnetic flux of the rotating magnetic field produced by the toroidal stator 12, generating a synchronous torque (see FIG. 7(C)). At this time, the superconducting rotating machine 100 rotates primarily due to the synchronous torque, and each rotor exhibits a torque characteristic corresponding to "synchronous rotation (superconducting state)" shown in FIG. 6. During this synchronous rotation, extremely slight slippage may occur due to the influence of the connection resistance between each rotor bar and the end ring, but in terms of the equipment characteristics, this can be regarded as synchronous rotation.

[0067] Even if an excessive load is applied to the superconducting rotating machine 100 during synchronous rotation, the superconducting squirrel-cage windings 22A and 32A transition to a flux flow state (see FIG. 7(B)), allowing the machine to continue operating primarily due to induced (slip) torque. The induced (slip) torque at this time is provided by both the normal conducting squirrel-cage windings 22B and 32B arranged next to the superconducting squirrel-cage windings 22A and 32A in the flux flow state, and each rotor exhibits torque characteristics corresponding to the "slip rotation (superconducting state)" shown in FIG.

[0068] In other words, the superconducting rotating machine 100 has torque characteristics for each rotor as shown in FIG. 6, and each rotor rotates primarily due to induced (slip) torque in the normal conductive state, and primarily due to synchronous torque under normal load and primarily due to induced (slip) torque under overload in the superconducting state.

[0069] [Method of driving a superconducting rotating machine] The superconducting rotating machine 100 configured as described above can be used in applications where rotating machines are used, such as automobiles (small cars, medium-sized cars, and large cars such as buses and trucks), railways, submarines, aircraft, and ships, and can be used, for example, in the superconducting motor system described in International Publication WO2009 / 116219.

[0070] For example, the superconducting rotating machine 100 can be applied to a system including a driven means such as a wheel, a propeller, a screw, etc. that rotates by being coupled to the rotating machine. The system includes, for example, the superconducting rotating machine 100, a driven means such as a wheel that is coupled to the superconducting rotating machine 100 directly or via another member, a cooling device that can cool the superconducting rotating machine 100 until it reaches a superconducting state, a control device that controls the cooling device in response to a cooling signal and also controls the superconducting rotating machine 100 via an inverter in response to a motor drive signal, and a battery for driving the superconducting rotating machine 100.

[0071] The cooling device is not particularly limited as long as it can cool the toroidal stator 12 and the superconducting squirrel-cage windings 22A and 32A using superconductivity in the superconducting rotating machine 100 until they reach a superconducting state (below the critical temperature). For example, a cooling device using helium gas, liquid nitrogen, or the like as a refrigerant can be used.

[0072] The control device is not particularly limited as long as it is a device that can drive and control the superconducting rotating machine 100 via a power supply device such as an inverter in response to a motor drive signal. For example, the control device controls the amplitude and frequency of an AC voltage applied to the stator winding 16 of the superconducting rotating machine 100 via a power supply device such as an inverter. In this way, the control device can feedback control the rotation speed and torque of the superconducting rotating machine 100. In addition, it is preferable that the control device stores in advance a slip rotation control pattern (first control pattern) used when the superconducting rotating machine 100 rotates mainly by induced (slip) torque, and a synchronous rotation control pattern (second control pattern) used when the superconducting rotating machine 100 rotates mainly by synchronous torque. Here, the slip rotation control pattern can be a known control pattern used for a conventional induction motor. Similarly, the synchronous rotation control pattern can be a known control pattern used for a conventional synchronous motor.

[0073] The control device can be configured to determine whether the superconducting squirrel-cage windings 22A and 32A are in a superconducting state (whether the superconducting rotating machine 100 is rotating mainly driven by synchronous torque) by monitoring a primary current signal, which is a signal of a primary current flowing in the stator winding 16, from the superconducting rotating machine 100. For example, if the rotor is rotating mainly driven by synchronous torque, the control device can be configured to apply a synchronous rotation control pattern to the superconducting rotating machine 100, and if not, the control device can be configured to apply a slip rotation control pattern assuming that the rotor is rotating mainly driven by induced (slip) torque.

[0074] Furthermore, when the superconducting squirrel-cage windings 22A and 32A are in a superconducting state without capturing the magnetic flux of the rotating magnetic field produced by the stator winding 16, the control device can be configured to increase the voltage applied to the stator winding 16 and / or the frequency of the applied voltage so as to bring the superconducting squirrel-cage windings 22A and 32A into a flux flow state. Once in the flux flow state, the superconducting squirrel-cage windings 22A and 32A can capture the interlinkage magnetic flux even in a state below the critical temperature.

[0075] For example, when the superconducting cage windings 22A and 32A have been cooled below the critical temperature by a cooling device before the start of operation, the superconducting cage windings 22A and 32A are in a superconducting state without capturing the magnetic flux from the stator winding 16. When an AC voltage is applied to the stator winding 16 in this state, a shielding current flows through the superconducting cage windings 22A and 32A, and the magnetic flux linking the superconducting cage windings 22A and 32A and the normal conductive cage windings 22B and 32B becomes zero (see FIG. 7(A)). In this case, no synchronous torque is generated, and no induced current flows through the normal conductive cage windings 22B and 32B, so that no induced (slip) torque is generated. Therefore, the superconducting rotating machine 100 cannot operate in this state.

[0076] Therefore, the control device increases the voltage applied to the stator winding 16 and / or the frequency of the applied voltage until the shielding current flowing through the superconducting squirrel-cage windings 22A and 32A exceeds the critical current, thereby putting the superconducting squirrel-cage windings 22A and 32A into a flux flow state. Since a finite resistance occurs in the flux flow state, magnetic flux can link to the superconducting squirrel-cage windings even if the temperature remains below the critical temperature (see FIG. 7(B)).

[0077] Thereafter, inner rotor 20 and outer rotor 30 are accelerated, and accordingly, when the rotating magnetic field and the relative speed between inner rotor 20 and outer rotor 30 become smaller, the current flowing through superconducting squirrel-cage windings 22A and 32A automatically becomes smaller. Finally, when the current flowing through superconducting squirrel-cage windings 22A and 32A falls below the critical current, superconducting squirrel-cage windings 22A and 32A capture the flux linkage (see FIG. 7(C)).

[0078] An example of a method for driving a system using the superconducting rotating machine 100 will be described below. However, the present invention is not limited to this embodiment. In the following, an example will be described in which a superconducting wire having a higher critical temperature than at least one of the superconducting wires used in the superconducting squirrel-cage windings 22A and 32A is used as the superconducting wire used in the stator winding 16 of the toroidal stator 12.

[0079] First, the stator winding 16 is cooled by a cooling device to a temperature lower than the critical temperature of the superconducting wire used in the winding in order to put the toroidal stator 12 into a superconducting state. At this time, the cooling temperature is set to a temperature lower than the critical temperature of the superconducting wire used in the stator winding 16 of the toroidal stator 12 and higher than the critical temperature of at least one of the superconducting wires used in the superconducting squirrel-cage windings 22A and 32A, and the superconducting rotating machine 100 is started in a state in which at least one of the superconducting squirrel-cage windings 22A and 32A is in a normal conducting state.

[0080] After the toroidal stator 12 becomes superconducting, in an initial state where the magnetic flux linking the superconducting squirrel-cage windings 22A and 32A is zero, an AC voltage is applied to the stator winding 16. At this time, if both the superconducting squirrel-cage windings 22A and 32A are cooled below their critical temperatures, i.e., if both the superconducting squirrel-cage windings 22A and 32A are in a superconducting state, and if the shielding currents flowing through the superconducting squirrel-cage windings 22A and 32A are less than their respective critical currents, even if a rotating magnetic field is generated inside and outside the stator winding 16, the magnetic flux linking the superconducting squirrel-cage windings 22A and 32A and the normal conducting squirrel-cage windings 22B and 32B becomes zero, and the superconducting rotating machine 100 does not operate.

[0081] In contrast, when a superconducting wire having a higher critical temperature than at least one of the superconducting wires used in the superconducting squirrel-cage windings 22A and 32A is used as the superconducting wire for the stator winding 16 of the toroidal stator 12, at least one of the superconducting squirrel-cage windings 22A and 32A is in a normal conducting state, so that in the rotor in a normal conducting state, the induced (slip) torque generated in the normal conducting squirrel-cage winding 22B or 32B becomes dominant. In other words, the superconducting rotating machine 100 rotates due to the induced (slip) torque of the rotor that is not in a superconducting state.

[0082] When either or both of the superconducting squirrel-cage windings 22A and 32A are in a normal conducting state, the cooling is continued, and the superconducting rotating machine 100 continues to operate as an induction motor until either one of the superconducting squirrel-cage windings 22A and 32A falls below the critical temperature.

[0083] After a predetermined time has elapsed, when both of the superconducting squirrel-cage windings 22A and 32A become below the critical temperature and transition to a superconducting state, the control device increases the voltage applied to the stator winding 16 and / or the frequency of the applied voltage until the shielding current flowing through the superconducting squirrel-cage windings 22A and 32A exceeds the critical current, thereby putting the superconducting squirrel-cage windings 22A and 32A into a flux flow state. In the flux flow state, as described above, magnetic flux can link to each superconducting squirrel-cage winding even if the temperature remains below the critical temperature.

[0084] Thereafter, inner rotor 20 and outer rotor 30 are accelerated, and as a result, the relative speed between the rotating magnetic field and inner rotor 20 and outer rotor 30 decreases, the current flowing through superconducting squirrel-cage windings 22A and 32A automatically decreases. Finally, when the current flowing through superconducting squirrel-cage windings 22A and 32A falls below the critical current, superconducting squirrel-cage windings 22A and 32A capture the interlinking magnetic flux. Then, superconducting rotating machine 100 rotates mainly by synchronous torque. Then, the control device applies a synchronous rotation control pattern to superconducting rotating machine 100 rotating mainly by synchronous torque, and drives and controls superconducting rotating machine 100. That is, in the superconducting state, superconducting rotating machine 100 exhibits torque characteristics corresponding to "synchronous rotation (superconducting state)" in FIG. 6.

[0085] [effect] According to the superconducting rotating machine 100 configured as above, a toroidal stator using superconducting wire is used as the stator, and therefore the critical current in the stator core is high. This makes it possible to increase the magnetic field strength generated from the stator, thereby improving the output (torque) of the rotating machine. Furthermore, according to the superconducting rotating machine 100, leakage magnetic flux generated on the outside of the toroidal stator can be converted into torque by the outer rotor 30. This makes it possible to increase the output of the rotating machine while achieving excellent energy conversion efficiency.

[0086] For example, under the following conditions, the superconducting rotating machines of the example and the comparative example were compared in terms of output (torque / Nm) versus drive time. In each example, a superconducting rotating machine having a toroidal stator, an inner rotor, and an outer rotor was used. In the comparative example, a superconducting rotating machine having a toroidal stator and an inner rotor was used. The following conditions are common to both the examples and the comparative example (the superconducting rotating machine of the comparative example does not have an outer rotor compared to the superconducting rotating machine of the examples). The results are shown in Figure 8. (conditions) Inner rotor outer diameter: 174.8mm Stator inner diameter: 176.0mm Stator outer diameter: 318.0mm Outer rotor inner diameter: 319.2mm Outer rotor outer diameter: 400.0mm ·Axis length: 102.0mm Number of turns per pole / phase: 12 Number of poles: 4 Gap length: 0.6mm Rotation speed: 1497rpm Slip: 0.00133 Current: 50A (effective value) Voltage: 82V (effective value) Frequency: 50Hz

[0087] In FIG. 8, the results of measuring the torque of both the inner rotor and the outer rotor using the superconducting rotating machine of the embodiment (hereinafter, Example (1)) are shown by a "dash line", the results of measuring only the torque of the inner rotor (hereinafter, Example (2)) are shown by a "bold line", and the results of measuring only the torque of the outer rotor (hereinafter, Example (3)) are shown by a "thin line". Also, the results of measuring the torque of the inner rotor using the superconducting rotating machine of the comparative example are shown by a "dashed line". As shown in FIG. 8, in Example (1) where the torque of both the inner rotor and the outer rotor were measured, the average torque was about 110 Nm from 0 to 0.1 seconds and was maintained at 100 Nm or more. In contrast, the average torque of the superconducting rotating machine of the comparative example (only the inner rotor) was about 60 Nm from 0 to 0.1 seconds. As a result, it was proven that the torque of the superconducting rotating machine of the embodiment was higher than that of the comparative example, and that it was excellent in energy efficiency. The torque of the inner rotor (Example (2)) and the torque of the outer rotor (Example (3)) in the superconducting rotating machine of the example were approximately 50 Nm and approximately 60 Nm, respectively, from 0 to 0.1 seconds.

[0088] Moreover, according to superconducting rotating machine 100, outer rotor 30 plays the role of a magnetic shield that prevents leakage magnetic flux from the radial outside of toroidal stator 12. Therefore, it is possible to suppress the influence of leakage magnetic flux from superconducting rotating machine 100 on peripheral devices without providing a separate magnetic shield.

[0089] Furthermore, superconducting rotating machine 100 is capable of both slip rotation and synchronous rotation because both the superconducting squirrel-cage winding (a) and the normal-conducting squirrel-cage winding (b) are used as rotor windings in inner rotor 20 and outer rotor 30. Therefore, it can operate with high efficiency during synchronous rotation, and can also operate with slip rotation even when out-of-synchronization occurs for some reason or until the superconducting state is reached.

[0090] Furthermore, the superconducting rotating machine 100 can be started by slip rotation by using a superconducting wire having a higher critical temperature than the critical temperature of at least one of the superconducting wires used in the superconducting squirrel-cage windings 22A and 32A as the superconducting wire used in the stator winding 16 of the toroidal stator 12. Therefore, at the time of starting, it is not necessary to put the superconducting squirrel-cage windings 22A and 32A into a flux flow state in order to increase the voltage applied to the stator winding 16 and / or the frequency of the applied voltage until the shielding current flowing through the superconducting squirrel-cage winding 22A or 32A exceeds the critical current, and the superconducting rotating machine 100 can be started smoothly.

[0091] In addition, in the superconducting rotating machine 100, the superconducting squirrel-cage windings 22A and 32A are made of superconducting wires, and therefore, when heat is generated, the heat is better dissipated than when a superconducting bulk material is used. In addition, the superconducting squirrel-cage windings 22A and 32A of the superconducting rotating machine 100 are made of superconducting wires with a small current capacity, and therefore, compared to when a superconducting bulk material with a large current capacity is used, the superconducting rotating machine 100 can easily capture the interlinkage magnetic flux and rotate synchronously by temporarily placing the superconducting squirrel-cage windings 22A and 32A in a flux flow state, even if the superconducting squirrel-cage windings 22A and 32A are in a superconducting state without capturing magnetic flux.

[0092] [Variations] Although the present embodiment has been specifically described above, the present embodiment can be modified as follows.

[0093] (First Modification) For example, in the above example, the embodiment in which both inner rotor 20 and outer rotor 30 have at least a superconducting squirrel-cage winding (a) and a normal conductive squirrel-cage winding (b) as rotor windings has been described, but the present invention is not limited to this embodiment. For example, superconducting rotating machine 100 may have an embodiment in which both inner rotor 20 and outer rotor 30 have only a normal conductive squirrel-cage winding (b). In this case, the superconducting rotating machine functions only as a slip rotating motor.

[0094] (Second Modification) The superconducting rotating machine 100 may be configured such that only one of the inner rotor and the outer rotor has at least a superconducting squirrel-cage winding (a) as a rotor winding. For example, while one of the rotors rotates in slip, the other rotor is controlled to be switched to synchronous rotation, thereby controlling the switching of the output (torque) of the rotating machine.

[0095] (Third Modification) Superconducting rotating machine 100 may be configured, for example, such that both inner rotor 20 and outer rotor 30 have only superconducting squirrel-cage windings (a). In this case, the superconducting rotating machine functions only as a rotary motor driven primarily by synchronous torque.

[0096] (Fourth Modification) In the superconducting rotating machine 100, the stator winding 16 of the toroidal stator 12 uses a superconducting wire having a higher critical temperature than the critical temperature of at least one of the superconducting wires used in the superconducting squirrel-cage windings 22A and 32A, but the present invention is not limited to this embodiment. For example, even if the critical temperature of the superconducting wire used in the stator winding 16 is equal to or lower than the critical temperature of the superconducting wire used in the superconducting squirrel-cage windings 22A and 32A, the superconducting rotating machine 100 can be started.

[0097] For example, when the stator winding 16 of the toroidal stator 12 and the superconducting squirrel-cage windings 22A and 32A are all in a superconducting state, as described above, the magnetic flux linking the superconducting squirrel-cage windings 22A and 32A and the normal-conducting squirrel-cage windings 22B and 32B is zero, and the superconducting rotating machine 100 does not operate. In this case, the control device can put the superconducting squirrel-cage windings 22A and 32A into a flux flow state by increasing the voltage applied to the stator winding 16 and / or the frequency of the applied voltage until the shielding current flowing through the superconducting squirrel-cage windings 22A and 32A exceeds the critical current. In the flux flow state, magnetic flux can link to the superconducting squirrel-cage windings even if the temperature remains below the critical temperature.

[0098] Thereafter, inner rotor 20 and outer rotor 30 are accelerated, and accordingly, when the relative speed between the rotating magnetic field and inner rotor 20 and outer rotor 30 decreases, the current flowing through superconducting squirrel-cage windings 22A and 32A automatically decreases. Finally, when the current flowing through superconducting squirrel-cage windings 22A and 32A falls below the critical current, superconducting squirrel-cage windings 22A and 32A capture the flux linkage. Then, superconducting motor 1 can be rotated mainly by the synchronous torque.

[0099] (Fifth Modification) Although the superconducting rotating machine 100 uses only superconducting wires in the stator winding 16 of the toroidal stator 12, the present invention is not limited to this embodiment. For example, the toroidal stator 12 may have another winding (normal conducting winding) using normal conducting wires in addition to the stator winding 16. In this case, for example, the superconducting rotating machine 100 can be configured so that magnetic poles are formed by normal conducting windings in the toroidal stator 12 and a rotating magnetic field can be generated even in a normal conducting state. With this configuration, for example, the superconducting rotating machine 100 can be started and driven even before the superconducting wires of the stator winding 16 become superconducting.

[0100] (Sixth Modification) In superconducting rotating machine 100, inner rotor 20 and outer rotor 30 have at least a superconducting squirrel-cage winding (a) as a rotor winding, and the critical current (A1) for putting superconducting squirrel-cage winding 22A of inner rotor 20 into a flux flow state and the critical current (A2) for putting superconducting squirrel-cage winding 32A of outer rotor 30 into a flux flow state can be configured to be different. With this configuration, for example, one rotor can be put into a flux flow state at a lower critical current than the other, so that the timing of capturing the interlinkage magnetic flux in the two rotors can be made different. This makes it possible to switch between a plurality of modes, such as both rotors rotating in slip, one rotor rotating in slip and the other rotor rotating synchronously, and both rotors rotating synchronously, according to the surrounding environment, remaining energy, energy efficiency, and other conditions.

[0101] (Seventh Modification) The superconducting rotating machine 100 can be configured such that the inner rotor 20 and the outer rotor 30 have at least a superconducting squirrel-cage winding (a) as a rotor winding, and a switching mechanism is provided that can switch between putting only one of the superconducting squirrel-cage winding 22A of the inner rotor 20 and the superconducting squirrel-cage winding 32A of the outer rotor 30 into a flux flow state, or putting the superconducting squirrel-cage windings of both rotors into a flux flow state. By providing the switching mechanism, it is possible to link the magnetic flux only to the rotor with a low critical current at a light load, while keeping the magnetic flux shielded from the other rotor with a high critical current. In order to suppress Joule loss and drive the superconducting rotating machine 100 with high efficiency, first, at a low load, output (drive) is performed at an appropriate load by only one of the rotors, thereby making it possible to drive the superconducting rotating machine 100 with high efficiency even at a low output. On the other hand, at high loads, highly efficient operation is possible by linking the magnetic flux to both of the two rotors to generate output. That is, by configuring the switching mechanism so that only one rotor can enter a magnetic flux flow state at low loads and both rotors can enter a magnetic flux flow state at high loads, the superconducting rotating machine 100 can be driven with high efficiency at both low and high loads.

[0102] The above-mentioned "switching mechanism" may be switched by a physical switch or a control means, and the means is not limited thereto. For example, by configuring superconducting squirrel-cage winding 22A of inner rotor 20 and superconducting squirrel-cage winding 32A of outer rotor 30 so that the critical currents for putting the two rotors into a flux flow state are different from each other, it is possible to autonomously switch between a mode in which only one of the superconducting squirrel-cage windings (a) of the inner rotor and the outer rotor is capable of being in a flux flow state and a mode in which both rotors are capable of being in a flux flow state according to the load (rotation speed) without providing a physical switch or the like. In other words, the difference in the critical currents for putting the two rotors into a flux flow state is the above-mentioned "switching mechanism." This eliminates the need to worry about the increase in size of the system and the effects of heat generation from the physical switch that accompany the installation of a physical switch, and also reduces the burden on the system due to switching control by a separate control means.

[0103] By setting the critical currents of the superconducting cage winding 22A of the inner rotor 20 and the superconducting cage winding 32A of the outer rotor 30 to be different, the mode in which only one of the superconducting cage windings of the inner rotor 20 and the outer rotor 30 can be in a magnetic flux flow state autonomously according to the load (rotation speed), and the mode in which both rotors can be in a magnetic flux flow state, will be switched. The principle will be explained. For example, let the critical current of the superconducting cage winding 22A of the inner rotor 20 be "Irc1", the critical current of the superconducting cage winding 32A of the outer rotor 30 be "Irc2", and "Irc1 < Irc2". However, the relationship between Irc1 and Irc2 in this embodiment is not limited to this.

[0104] First, when a voltage is applied to the primary stator winding and a primary current Is is made to flow as "Is1", the current Ir1 flowing through the superconducting cage winding 22A of the inner rotor 20 and the current Ir2 flowing through the superconducting cage winding 32A of the outer rotor 30, when each satisfies the conditions of "Ir1 < Irc1" and "Ir2 < Irc2", that is, when each of Ir1 and Ir2 is smaller than the critical currents Irc1 and Irc2, the magnetic flux created by the stator winding is not linked, and the rotor does not start.

[0105] Next, the stator current is increased. When it reaches Is = Is2 (Is2 > Is1), if Ir1 > Irc1 and Ir2 < Irc2 (that is, when Ir1 becomes greater than the critical current Irc1), the magnetic flux created by the stator winding only links with the superconducting cage winding 22A of the inner rotor 20, and the inner rotor 20 starts to rotate. Also, when the inner rotor 20 and the outer rotor are fixed to the same shaft as shown in FIG. 2, the inner rotor 20 and the outer rotor start simultaneously. At this time, if the turn ratio between the stator winding and the superconducting cage winding 22A of the inner rotor 20 is set to n1 (>1), and the turn ratio between the stator winding and the superconducting cage winding 32A of the outer rotor 30 is set to n2 (>1), although not exact values, Is2 can be regarded as approximately the sum of the currents flowing through "Ir1 / n1" and "Ir2 / n2". After starting and reaching the synchronous speed, Ir2 stabilizes at a current value that balances the load. When it stabilizes at the current value that balances the load, if the current value of the superconducting cage winding 22A of the inner rotor 20 is Ir1,st (<Irc1), and the current value of the superconducting cage winding 32A of the outer rotor 30 is Ir2,st (<Irc2), since Irc1 < Irc2, at this time, Is is only Ir1,st / n1, that is, it only flows through the superconducting cage winding 22A of the inner rotor 20, Is is small, and the Joule loss generated in the winding is also small. That is, for example, when the critical currents of the superconducting cage winding 32A of the outer rotor 30 and the superconducting cage winding 22A of the inner rotor 20 are the same (when Irc1 = Irc2), strictly speaking, since the sizes of the windings are different between the inner and outer in the radial direction, although it is assumed that the winding impedances are different even if the critical currents are the same, Is can be roughly regarded as "Ir1,st / n1" + "Ir1,st / n2". In this case, Is becomes large and the Joule loss becomes large. Therefore, at light loads, by allowing the magnetic flux to link with only one rotor (in the above case, the inner rotor 20) (in the above case, by having only the inner rotor 20 bear the output), the Joule loss can be reduced.

[0106] On the other hand, when the load increases, Ir1,st increases, but when Ir1,st>Irc1, the magnetic flux from the rotor interlinks with inner rotor 20 and the rotor transitions to slip rotation. At this time, if Ir2,st>Irc2 is satisfied immediately at the timing when inner rotor 20 transitions to slip rotation, superconducting squirrel-cage winding 32A of outer rotor 30 captures the magnetic flux and the rotor transitions to synchronous rotation. On the other hand, if Ir2,st>Irc2 is not satisfied immediately, the load increases further, Ir2,st>Irc2, the magnetic flux from the stator interlinks with outer rotor 30, and the rotor transitions to slip rotation. At this point, superconducting squirrel-cage winding 32A of outer rotor 30 captures the magnetic flux, the rotor transitions to synchronous rotation, and both outer rotor 30 and inner rotor 20 provide output. As described above, under light loads, magnetic flux is captured and output only by superconducting squirrel-cage winding 22A rotor winding of inner rotor 20, thereby making it possible to reduce loss compared to the case where the magnetic flux is output by linking to both rotor windings.

[0107] (Eighth Modification) Although the superconducting rotating machine 100 has been described as having the inner rotor 20 and the outer rotor 30 fixed coaxially and generating output (torque) from a single rotating shaft, the present invention is not limited to this embodiment. For example, in the superconducting rotating machine 100, the inner rotor 20 and the outer rotor 30 are integrally configured, but the inner rotor and the outer rotor may be configured to rotate independently. Figure 9 is an explanatory diagram showing an axial cross section of another example of a superconducting rotating machine. Note that in Figure 9, the same reference numbers are used for the same members as in Figure 2, and their description will be omitted.

[0108] As shown in Fig. 9, superconducting rotating machine 200 includes toroidal stator 12, inner rotor 60, and outer rotor 70. Rotating shaft 60A is connected to one end of inner rotor 60. Rotating shaft 70A is connected to one end of outer rotor 70, and inner rotor 60 and outer rotor 70 are configured to be rotatable independently.

[0109] This configuration can realize, for example, a configuration in which the rotation speed (RS1) of the inner rotor and the rotation speed (RS2) of the outer rotor are different. Also, this configuration can realize a configuration in which the inner rotor or the outer rotor can rotate while the other rotor is stopped.

[0110] According to these configurations, as in the sixth modified example described above, the rotation speeds of both rotors and switching between rotation and stop can be performed according to the surrounding environment, remaining energy, energy efficiency, and other conditions.

[0111] (Other variations) For example, the above-mentioned superconducting wire is not limited to bismuth-based high-temperature superconducting wire, but may be a metal-based low-temperature superconducting wire represented by NbTi or Nb3Sn, an yttrium-based high-temperature superconducting wire, or a magnesium diboride superconducting wire.

[0112] In the above embodiment, the wire material is used as the superconducting material and the normal conducting material, but the present invention is not limited to this embodiment, and bulk materials may be used as the superconducting material and the normal conducting material. For example, bulk materials can be used as the superconducting material and / or the normal conducting material depending on the application where it is desired to use a material with a large current capacity in the stator or rotor (for example, a large superconducting motor, etc.).

[0113] In the above embodiment, the superconducting squirrel-cage windings 22A and 32A and the normal conductive squirrel-cage windings 22B and 32B are separate bodies, but they may be configured as an integrated body. That is, the highly conductive metal in the superconducting wire of the superconducting squirrel-cage windings 22A and 32A may be made to have a predetermined thickness or more, and the highly conductive metal part may be the normal conductive squirrel-cage windings 22B and 32B.

[0114] In the above embodiment, in inner rotor 20, normal conducting squirrel cage winding 22B is arranged on the outside of inner rotor 20 and superconducting squirrel cage winding 22A is arranged on the inside thereof, but superconducting squirrel cage winding 22A may be arranged on the outside. When normal conducting squirrel cage winding 22B is arranged on the outside, the induced (slip) torque in the normal conducting state and the induced (slip) torque in the superconducting state can be increased, and when superconducting squirrel cage winding 22A is arranged on the outside, the synchronous torque in the superconducting state can be increased. Similarly, the arrangement of superconducting squirrel cage winding 32A and normal conducting squirrel cage winding 32B in outer rotor 30 may be changed.

[0115] Furthermore, in the above embodiment, the superconducting squirrel cage windings 22A and 32A and the normal conductive squirrel cage windings 22B and 32B are accommodated one by one in the slot 34S, but this is not limited to the above. For example, a slot for accommodating the superconducting squirrel cage windings 22A and 32A and a slot for accommodating the normal conductive squirrel cage windings 22B and 32B may be provided separately. In this case, the number of rotor bars 26A of the superconducting squirrel cage windings 22A and 32A and the number of rotor bars 26B of the normal conductive squirrel cage windings 22B and 32B may not be the same. Also, some of the rotor bars 26A, 74a may be accommodated in the same slot, and the remaining may be accommodated in different slots.

[0116] Although various embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments. In addition, the present invention can be modified without departing from the spirit of the present invention.

[0117] The disclosure of Japanese Patent Application No. 2020-056792, filed on March 26, 2020, is incorporated herein by reference in its entirety. In addition, all publications, patent applications, and technical standards mentioned in the specification are herein incorporated by reference to the same extent as if each individual publication, patent application, and technical standard was specifically and individually indicated to be incorporated by reference. [Explanation of symbols]

[0118] 12: toroidal stator, 14: stator core, 16: stator winding, 20, 60: inner rotor, 22A, 32A: superconducting squirrel cage winding, 22B, 32B: normal conducting squirrel cage winding, 24S, 34S: slots, 26A, 26B, 36A, 36B: rotor bars, 28A, 28B, 38A, 38B: end rings, 30, 70: outer rotor, 100, 200: superconducting rotating machine

Claims

1. a stator having a cylindrical stator core and a stator winding wound in a toroidal shape around the stator core and made of a superconducting material, the stator generating a rotating magnetic field on the inner and outer circumferential sides of the stator; an inner rotor rotatably supported on an inner circumferential side of the stator; an outer rotor rotatably supported on an outer periphery of the stator; Equipped with The inner rotor and the outer rotor each have At least one rotor winding selected from a superconducting cage winding (a) having rotor bars and end rings formed of one or more superconducting materials and a normal conductive cage winding (b) having rotor bars and end rings formed of one or more normal conductive materials; a rotor core having a plurality of slots for receiving each rotor bar of the rotor winding; A superconducting rotating machine having the above structure.

2. 2. The superconducting rotating machine according to claim 1, wherein at least one of the inner rotor and the outer rotor has at least a superconducting squirrel-cage winding (a) as the rotor winding.

3. 3. The superconducting rotating machine according to claim 1, wherein at least one of the inner rotor and the outer rotor has a superconducting squirrel-cage winding (a) and a normal conducting squirrel-cage winding (b) as the rotor winding.

4. 4. The superconducting rotating machine according to claim 1, wherein the inner rotor and the outer rotor have at least a superconducting squirrel-cage winding (a) as the rotor winding.

5. 5. The superconducting rotating machine according to claim 3, wherein the inner rotor and the outer rotor have at least a superconducting squirrel-cage winding (a) as the rotor winding, and a critical current (A1) for putting the superconducting squirrel-cage winding (a-1) of the inner rotor into a magnetic flux flow state is different from a critical current (A2) for putting the superconducting squirrel-cage winding (a-2) of the outer rotor into a magnetic flux flow state.

6. 5. The superconducting rotating machine according to claim 1, wherein the inner rotor and the outer rotor have at least a superconducting squirrel-cage winding (a) as the rotor winding, and only one of the superconducting squirrel-cage winding (a) of the inner rotor or the outer rotor can be switched to a magnetic flux flow state.

7. 7. The superconducting rotating machine according to claim 6, wherein a critical current (A1) for putting the superconducting squirrel-cage winding (a-1) of the inner rotor into a flux flow state and a critical current (A2) for putting the superconducting squirrel-cage winding (a-2) of the outer rotor into a flux flow state are different, and only one of the superconducting squirrel-cage windings (a) of the inner rotor and the outer rotor can be switched into the flux flow state depending on the difference between the critical current (A1) and the critical current (A2).

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