JP2012059511A - Single core superconducting wire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly efficient single core superconducting wire of low loss based on self-magnetic field.SOLUTION: A stabilization layer 2 consisting of a low resistance material is arranged on the inside of a single core superconducting wire 1 having a circular cross-section, and a superconducting layer 3 consisting of a superconductor is arranged on the outside of the stabilization layer 2. The superconductor is formed continuously in the circumferential direction in the cross-section of the superconducting layer 3 perpendicular to the longitudinal direction. When the low resistance material is copper (Cu) and the superconductor is magnesium diboride (MgB), a barrier layer 4 is provided between the stabilization layer 2 and the superconducting layer 3. A high resistance sheath layer 5 consisting of a high resistance material is arranged on the outside of the superconducting layer 3.

Description

  The present invention relates to a single-core superconducting wire used for a coil of a superconducting motor.

  The possibility of using hydrogen is being studied as a technology for correcting energy and environmental problems. In order to oxidize hydrogen and continue to generate energy in a fuel cell or the like, it is necessary to construct a system that safely, stably manufactures, transports, stores, and transfers hydrogen. At that time, it is indispensable to use hydrogen not only as a compressed gas but also as a liquefied gas. This is because the volume density of liquid hydrogen or slush hydrogen is much larger than that of compressed gas, and the storage efficiency is excellent (see Non-Patent Document 1).

  Therefore, a superconducting motor has been proposed as a means for circulating or transferring liquid hydrogen or slush hydrogen (see Non-Patent Document 2). In this motor, the liquid hydrogen itself to be transferred functions as a refrigerant, so there is no need to consider the cooling penalty, and it is expected to drive the liquid hydrogen pump with much lower power consumption than the normal motor. . In other words, when superconducting wire is applied to the rotor winding of a squirrel-cage induction motor, as already demonstrated in Non-Patent Document 3-8, loss in a cryogenic environment can be significantly suppressed by synchronous rotation of the motor. In addition, torque and output can be greatly improved compared to conventional machines. In addition, if the stator winding through which three-phase AC flows is also composed of superconducting wires, the loss generated in the primary winding is greatly reduced compared to the case where the copper winding of the conventional machine is cooled to the liquid hydrogen temperature. It is expected.

Further, as a technique using a superconductor, for example, in Patent Document 1, a plurality of superconductors (tape-shaped superconductors) are arranged around a plurality of filaments made of a copper alloy and magnetically separated from the outside. A superconducting cable having a structure in which the body is arranged in a spiral shape, in Patent Document 2, a single-wire material formed of an Nb-Al composite in the Nb ₃ Al compound-based superconducting wire, with a stabilizing material disposed therein A structure in which a plurality of components are arranged is disclosed.

R.D.McCarty: "Hydrogen technology survey-Thermophysical properties," NASA Special Publication (1975) SP-3089. K. Kajikawa and T. Nakamura: "Proposal of a fully superconducting motor for liquid hydrogen pump with MgB2 wire," IEEE Trans. Appl.Supercond., Vol.19, No.3 (2009) pp.1669-1673. J. Sim, M. Park, H. Lim, G. Cha, J. Ji and J. Lee: "Test of an induction motor with HTS wire at end ring and bars," IEEE Trans. Appl. Supercond., Vol. 13, No.2 (2003) pp.2231-2234. J. Sim, K. Lee, G. Cha and J.-K. Lee: "Development of a HTS squirrel cage induction motor with HTS rotor bars," IEEE Trans. Appl. Supercond., Vol. 14, No. 2 ( 2004) pp.916-919. T. Nakamura, H. Miyake, Y. Ogama, G. Morita, I. Muta and T. Hoshino: "Fabrication and characteristics of HTS induction motor by the use of Bi-2223 / Ag squirrel-cage rotor," IEEE Trans. Appl.Supercond., Vol.16, No.2 (2006) pp.1469-1472. G. Morita, T. Nakamura and I. Muta: "Theoretical analysis of a YBCO squirrel-cage type induction motor based on an equivalent circuit," Supercond. Sci. Technol., Vol. 19, No. 6 (2006) pp. 473-478. T. Nakamura, Y, Ogama, H. Miyake, K. Nagao and T. Nishimura: "Novel rotating characteristics of a squirrel-cage-type HTS induction / synchronous motor," Supercond. Sci. Technol., Vol. 20, No .10 (2007) pp.911-918. T.Nakamura, K.Nagao, T.Nishimura, Y.Ogama, M.Kawamoto, T.Okazaki, N.Ayai and H.Oyama: "The direct relationship between output power and current carrying capability of rotor bars in HTS induction / synchronous motor with the use of DI-BSCCO tapes, "Supercond. Sci. Techno1., Vol.21, No.8 (2008) 085006.

Special table 2007-536700 gazette JP 2001-52547 A

  However, if a three-phase AC current is applied to the stator windings that constitute the motor described in Non-Patent Document 2-8, a large Joule loss or eddy current loss occurs when a copper wire similar to the conventional machine is applied. In addition, when superconducting wire is used, AC loss such as electromagnetic loss (historical loss) associated with the pinning mechanism of superconductors and eddy current loss generated in normal metal parts occurs. Cannot be realized.

  Further, as is clear from the techniques described in Patent Documents 1 and 2 that the superconductor has a multi-core structure, in order to pass a current by twisting the superconductor spirally, A self-magnetic field in the longitudinal direction of the conductor (a magnetic field generated by the current flowing through itself) is also generated on the inner side, and an AC loss such as eddy current is generated in the normal metal part (copper alloy, etc.) inside, resulting in efficient current flow. Can not be energized.

  Therefore, the present invention provides a low-loss and high-efficiency single-core superconducting wire mainly composed of a self-magnetic field, unlike the above-described superconducting cables and multi-core superconducting wires mainly composed of an external magnetic field. To do.

  In the single-core superconducting wire disclosed in the present application, a stabilizing layer made of a low resistance material is disposed inside a superconducting wire having a circular cross section, and a superconducting layer made of a superconductor is disposed outside the stabilizing layer. The superconducting layer is formed by continuously forming the superconductor in the circumferential direction in a cross section perpendicular to the longitudinal direction.

  As described above, in the single-core superconducting wire disclosed in the present application, the low-resistance material stabilizing layer is disposed on the inner side, and the superconducting layer made of a superconductor is disposed on the outer side. Induction of eddy currents in the low-resistance material due to the current flowing through the layers can be eliminated, and the AC loss can be reduced. Also, since the superconducting layer is a single core that continuously forms the superconductor in the circumferential direction in a cross section perpendicular to the longitudinal direction, it can be formed inside by spiraling like a multicore structure. There is no self-magnetic field, and there is an effect that AC loss can be reduced by eliminating induction of eddy currents in the low-resistance material.

Further, by providing the stabilization layer of the low resistance material on the inner side, the outer diameter of the superconducting layer becomes relatively large, and it is possible to reduce the history loss. That is, assuming that the inner diameter of the superconducting layer is R ₀ and the outer diameter is R ₁ , the hysteresis loss Q per unit length based on the Bean model is expressed by the following equation.

Here, i _m is the energizing current amplitude normalized by the critical current I _c, which is ^{_{Q 0 = μ 0 I c 2}} / π, c = 1-R 0 2 / R 1 2. Since the hysteresis loss of the superconducting layer is proportional to c from the formula (1), the superconducting layer is cylindrical (the inside is hollow and a low resistance material is disposed in the hollow region). It can be seen that the hysteresis loss can be reduced because the outer diameter R ₁ is relatively increased and c is decreased.

In the single-core superconducting wire disclosed in the present application, the low-resistance material is copper (Cu), the superconductor is magnesium diboride (MgB ₂ ), and between the stabilization layer and the superconducting layer. And a barrier layer for preventing the reaction between the copper and magnesium diboride.

As described above, the single-core superconducting wire disclosed in the present application has a barrier layer between the low-resistance material Cu and the superconductor MgB ₂ , thereby reliably preventing the reaction between Cu and MgB _2. Thus, there is an effect that a high-performance single-core superconducting wire can be formed.

The single-core superconducting wire disclosed in the present application is characterized in that the low-resistance material is pure iron.
Thus, in the single-core superconducting wire disclosed in the present application, the low-resistance material is pure iron, so that it has a function as a stabilizing layer and prevents a binding reaction between the stabilizing layer and the superconducting layer. It has a function as a barrier layer, and has the effect of simplifying the manufacturing process and increasing work efficiency.

In the single-core superconducting wire disclosed in the present application, a high-resistance sheath is disposed outside the superconducting layer.
As described above, in the single-core superconducting wire disclosed in the present application, since the high-resistance sheath is disposed outside the superconducting layer, the superconducting layer is reliably protected, and a large current flowing through the superconducting layer is used. An eddy current induced in the sheath is unlikely to occur, and an AC loss can be reduced.

The single-core superconducting wire disclosed in the present application is a coil in which the single-core superconducting wire is housed and wound in a recess in the iron core of a stator of a superconducting rotating machine.
As described above, in the single-core superconducting wire disclosed in the present application, the single-core superconducting wire is a coil that is housed and wound in the recess in the iron core of the stator of the superconducting rotating machine. There is an effect that it is possible to realize a highly efficient superconducting rotating machine with reduced AC loss in the main electromagnetic environment. Further, since the AC loss can be reduced, the coil can be thinned, and the superconducting rotating machine can be miniaturized. Further, by thinning the coil, it is possible to ensure a large distance between the recesses in the iron core of the stator, and it is possible to realize a high-performance rotating machine by increasing the gap magnetic field.

It is a figure which shows the characteristic of the superconducting wire as a sample for measuring an alternating current loss. It is a figure which shows the energization loss per unit length and 1 period of a sample wire. It is a figure which shows the result of having measured the alternating current loss in the range of frequency 10-100Hz with a constant load factor. It is a figure which shows the current amplitude dependence of the superconducting part at the time of alternating current supply, the Nb layer of a sheath material, Cu layer, and the whole loss. It is a figure which shows the numerical calculation result of the current distribution in a sample wire. It is a figure which shows magnetic field distribution in a wire when an alternating current is passed through a MgB ₂ sample wire. It is a figure which shows the cross section of the single core superconducting wire which concerns on 1st Embodiment. It compares the AC loss calculation result of the whole wire per unit length about the single core superconducting wire which concerns on 1st Embodiment. It is a schematic diagram of the stator of the superconducting motor using the single core superconducting wire which concerns on 1st Embodiment.

  Embodiments of the present invention will be described below. The present invention can be implemented in many different forms. Also, the same reference numerals are given to the same elements throughout the present embodiment.

(First embodiment of the present invention)
A single-core superconducting wire according to this embodiment will be described with reference to FIGS. FIG. 1 is a diagram showing characteristics of a superconducting wire as a sample for measuring AC loss, FIG. 2 is a diagram showing a unit length of a sample wire, and a conduction loss per cycle, and FIG. 3 is a load factor. The figure which shows the result of having measured the alternating current loss in the range of frequency 10-100Hz with constant, FIG. 4 shows the current amplitude dependence of the superconducting part at the time of alternating current supply, the Nb layer of a sheath material, Cu layer, and the whole loss. FIG. 5 is a diagram showing a numerical calculation result of current distribution in the sample wire, FIG. 6 is a diagram showing a magnetic field distribution in the wire when an alternating current is passed through the MgB ₂ sample wire, and FIG. FIG. 8 is a diagram showing a cross section of a single-core superconducting wire according to the embodiment, FIG. 8 is a comparison of AC loss calculation results of the entire wire per unit length for the single-core superconducting wire according to the present embodiment, FIG. It is a schematic diagram of a stator of a superconducting motor using a single core superconducting wire according to the present embodiment. .

In the present embodiment, a single-core superconducting wire using magnesium diboride (MgB ₂ ) as a superconductor will be described. MgB ₂ is a new metallic superconductor discovered at the beginning of the 21st century. It has a superconducting transition temperature (critical temperature) of about 39K and is electrically charged in liquid hydrogen having a boiling point of about 20K under atmospheric pressure. Superconducting state without resistance can be maintained. However, since the critical current density of the current MgB ₂ wire is drastically reduced when an external magnetic field of several Tesla is applied at 20K, it includes the case where the main magnetic field (the magnetic field generated by the current flowing through itself) is the main component. Low magnetic field applications are considered appropriate.

First, the AC loss characteristic of the MgB ₂ single core wire, which has been found by the inventors of the present application as a result of diligent efforts, will be described.
(1) Measurement of current loss Table 1 below shows the specifications of the sample wire. The sample wire is a single core structure wire using Cu and niobium (Nb) as a sheath material, the wire diameter 2R ₃ is 0.8 mm, the outer diameter 2R _{2 of} Nb is 0.685 mm, and the outer diameter 2R ₁ of the superconducting filament is 0.555 mm.

Moreover, sectional drawing of a sample wire and the temperature characteristic of a resistivity are shown to Fig.1 (a), (b). A 1 A direct current is passed through the wire, and the resistivity is determined by measuring the voltage generated between the voltage taps provided on the wire. From FIG. 1B, the critical temperature T _c of the MgB ₂ sample wire is 36K. Assuming that the resistivity of MgB ₂ is very large and that of the metal sheath part, the resistance value is constant at 20K or less (26.4K and 30.30). 3K) extrapolate the resistivity of the metal sheath. The resistivity of Cu is obtained from the resistivity of the metal sheath portion and the resistivity of Nb at the test temperature.

  The current loss is measured by a so-called four-terminal method in a self-magnetic field. Temperature control is conduction cooling by helium gas flow and is adjusted by the heater and gas flow rate. The sample holder is composed of a copper block, and an aluminum nitride substrate having a good thermal conductivity is disposed between the sample and the sample holder with an electrical insulating material. The sample temperature is measured by a temperature sensor installed near the sample on this substrate. The measurement temperature is 26.4K and 30.3K, and the temperature stability during measurement is in the range of ± 0.1K. The voltage between taps of the sample wire is measured by a lock-in amplifier using the oscillator signal as a reference signal. The distance between taps is 10 mm. In addition, the phase shift generated in the measurement system is corrected using the signal of the induction coil under liquid nitrogen temperature installed in the circuit.

The unit length of the sample wire and the energization loss per cycle are shown in FIG. The frequencies are 50 Hz and 100 Hz. Load factor i _m = I _m / I _c on the horizontal axis, is obtained by normalizing the current amplitude I _m in the critical current I _c. Moreover, the curve is the unit length of the round line when assuming a Bean model with a constant critical current density, the conduction loss per cycle,

Here, Q ₀ = μ ₀ I _c ² / π. From this figure, it can be seen that the energization loss decreases as the temperature increases. This is because the critical current decreases when the temperature is high due to the temperature dependence of the critical current. Next, FIG. 3 shows the result of measurement in a frequency range of 10 to 100 Hz with a constant load factor. From this figure, it can be seen that the loss increases somewhat at higher frequencies. This is presumably because an eddy current loss depending on the frequency of the energized current occurred in the metal sheath portion.

Here numerical analysis of (2) current loss, superconducting filament diameter 2R _l, respectively the outer diameter of the Nb and Cu sheath portion considered infinite length superconducting round wire model 2R _2, 2R _3, the superconducting wire Numerical analysis of AC loss was performed. When the central axis in the longitudinal direction is the z axis and an alternating current I is applied in the z direction, the electromagnetic field in the superconducting round wire is a one-dimensional Maxwell equation.

  Satisfied. Here, B is the local magnetic flux density in the θ direction, and E and J are the local electric field and current density in the z direction, respectively. However, in the equation (4), the term of displacement current is ignored. The EJ characteristics of the sample wire are obtained by applying an n-value model to the superconductor part and Ohm's law to the metal sheath part.

It becomes. Here, J _c is the critical current density, E _c is the electric field reference, and ρ _m is the resistivity of the metal sheath part. The boundary condition is given by the following equation.

Here, I _m is the current amplitude, and ω is the angular frequency. Numerical analysis of temporal changes in electromagnetic field distribution in a round wire is performed by a one-dimensional difference method in which equations (3) and (4) are discretized at equal intervals in the radial direction (for example, Yuichi Terasawa, “Oxide Superconducting Wires”). Proposal of a simple method for evaluating current loss ”, see Kyushu University Graduate School of Systems and Information Sciences, Department of Electrical and Electronic Systems Engineering, 2002, p.10). From the obtained electromagnetic field distribution, the unit length of each part and the AC loss Q per cycle are:

Given in. Here, r is a radial region of each part.

  FIG. 4 (a) shows the current amplitude dependence of the superconducting portion, the Nb layer of the sheath material, the Cu layer, and the overall loss during 50 Hz alternating current energization at 26.4K. In addition, the experimental results of current loss are also displayed. From this figure, it can be seen that the numerical calculation results of the total AC loss agree well with the experimental results. In addition, the numerical calculation result of the loss of the superconducting part agrees well with the theoretical value by the Bean model. Furthermore, although the loss of the Nb sheath portion is very small and can be ignored, the loss of the Cu sheath portion cannot be ignored and it can be seen that the loss is the same as the loss of the superconducting portion. From the above, since the loss of the Cu sheath portion is relatively large, it can be said that the experimental result is larger than the theoretical value based on the Bean model.

  The result at the time of 100 Hz alternating current energization in 26.4K of Drawing 4 (b), the result at the time of 50 Hz alternating current energization in 30.3K of Drawing 4 (c), and the result at the time of 100 Hz alternating current energization in 30.3K of Drawing 4 (d) Is similar to the above result. However, in the result at 30.3 K, when the current amplitude is large, the experimental result is somewhat larger than the numerical calculation result, but it is considered that the temperature of the sample wire is rising due to heat generation due to AC loss. The results indicated by the triangle (▲) and rhombus (♦) symbols in FIGS. 4A to 4D will be described later.

  Next, the numerical calculation result of the current distribution in the sample wire is shown in FIG. The load factor is taken on the horizontal axis, and the ratio of the current flowing through each part is shown with the total current being 1. From this result, it can be seen that the current flowing through the metal sheath portion is negligibly small and almost flows through the superconducting portion. However, the current flowing through the superconducting portion is somewhat reduced near the critical current value.

(3) Theoretical expression of eddy current loss From FIG. 5, it is assumed that most current flows only in the superconducting part because most of the current flows in the superconducting part when the MgB ₂ sample wire is energized. The theoretical expression of the eddy current loss generated in the metal sheath part is derived. First, FIG. 6 shows the magnetic field distribution in the wire when an alternating current is passed through the MgB ₂ sample wire. The magnetic field B _i (t) and the maximum magnetic field B _{im on the} surface of the superconductor are obtained by using a conduction current I (t) (= I _m cosωt).

It is expressed. The magnetic flux front position r ₁ at the AC peak is given by the following equation.

Where B _p is the center reaching magnetic field,

It is expressed as Further, the bending position r ₂ of the magnetic flux in the demagnetization process is given by the following equation.

Therefore, if the interlinkage magnetic flux inside the superconductor is Φ, the electric field E (R ₁ ) on the superconductor surface is

It can be expressed as Further, when the pointing vector on the surface of the superconducting filament is integrated over one period using the equation (13), the same result as the equation (2) is obtained. Next, the induced electric field outside the superconducting filament is

It becomes. Therefore, the loss Q _e in the metal sheath portion is

It is expressed as Here, f is the _{frequency, S m, ρ m, r} m cross-sectional area of each of the metal sheath, the resistivity, the average radius. From this theory table type, an eddy current loss is proportional to the reciprocal of the frequency f resistivity [rho _m.

Here, the current amplitude dependence of AC loss will be described. The triangular symbols (▲) and rhombus symbols (♦) in FIGS. 4A to 4D indicate the eddy current loss per unit length and one unit length in the Cu sheath portion and Nb sheath portion obtained from the theoretical expression. The current amplitude dependency is shown. From these figures, it can be said that the calculated theoretical expression of the eddy current loss reproduces the numerical analysis result very well. The eddy current loss is proportional to the square when the amplitude is small and proportional to the cube when it is large. Further, the current amplitude I _m from Fig approaches the critical current I _c, since all of the current diverted some of the current to the Cu sheath can not hold the assumption that flows through the superconducting part, theoretical values numerical results It turns out that it becomes larger. From the above, it can be said that the loss observed in the metal sheath portion of the MgB ₂ sample wire is an eddy current loss, and the obtained theoretical expression well explains it.

As described above, the conduction loss of the wire having the structure as shown in FIG. 1A is given by the sum of the hysteresis loss of the MgB ₂ filament portion based on the Bean model and the eddy current loss of the Cu sheath portion. In other words, the loss of the Nb sheath portion having a relatively large resistivity is very small and can be ignored, but an eddy current is induced in the Cu sheath portion having a relatively small resistivity by the most energized current flowing in the MgB ₂ filament portion. Thus, an AC loss larger than the theoretical expression based on the Bean model is generated.

Therefore, the structure of the superconducting wire is a single-core superconducting wire as shown in FIG. FIG. 7A shows a single-core superconducting wire 1 having a structure in which a barrier layer 4 is disposed between a stabilization layer 2 made of a low resistance material and a superconducting layer 3 made of a superconductor. (B) is a single-core superconducting wire 1 having a structure in which the barrier layer 4 is not disposed between the stabilization layer 2 and the superconducting layer 3, and FIG. This is a magnetic field distribution in the wire when a current flows only in the superconducting layer 3 of the core superconducting wire. When the superconductor is MgB ₂ and the low resistance material is Cu, MgB ₂ and Cu react in the manufacturing process of the single-core superconducting wire 1, so that the barrier layer 4 is necessary. On the other hand, when the superconductor is MgB ₂ and the low-resistance material is pure iron, pure iron can also serve as the barrier layer 4 in the manufacturing process of the single-core superconducting wire 1. There is no need to form layer 4. Therefore, depending on the material, it is determined whether the structure shown in FIG. 7A or the structure shown in FIG.

Further, assuming that the inner radius of the superconducting layer 3 is R ₀ and the outer radius is R ₁ , the hysteresis loss Q per unit length based on the Bean model is expressed by equation (1), and is proportional to the geometric coefficient c. 7A and 7B having the stabilization layer 2 inside the superconducting layer 3, the superconducting layer 3 becomes cylindrical and the outer radius R ₁ is relatively It becomes larger and c becomes smaller, and history loss becomes smaller. Further, a high resistance sheath layer 5 made of a high resistance material is disposed outside the superconductive layer 3. The high resistance sheath layer 5 reliably protects the superconducting layer 4 and the high resistance sheath layer 5 has a high resistance, so that eddy currents induced by most of the current flowing through the superconducting layer 4 are unlikely to occur. Thus, AC loss can be reduced.

  When the current flows only in the superconducting layer 3, the magnetic field has a distribution as shown in FIG. 7C. As is clear from this figure, the stabilizing layer 2 inside the superconducting layer 3 has a zero magnetic field. It can be seen that it is. That is, the eddy current in the stabilization layer as shown in FIG. 6 is eliminated, and the AC loss can be reduced.

  In order to confirm the loss reduction effect in the structure of FIG. 7A, the result of comparison with the structure of FIG. 1A will be described. First, an n-value model is assumed as the EJ characteristic of the superconducting portion, and the cross-sectional area of each layer of the single-core superconducting wire 1 is designed under the same conditions as in FIG. It is assumed that the n value is the same as that in FIG. In the numerical analysis, the time change of the electromagnetic field distribution is obtained by using a one-dimensional difference method in which the radial direction of the cylindrical coordinate system is discretized at equal intervals. From the electromagnetic field distribution obtained by the difference method, the AC loss is obtained by spatially integrating the product of the local electric field and the current density in the radial direction and integrating over time over one period.

FIG. 8 shows a comparison of AC loss calculation results of the entire wire per unit length at 26.4K and 100 Hz as an analysis result. At this time, the wire diameter is 0.8 mm, the critical current I _c is 192 A, and the n value is 116. From FIG. 8, it is clear that in the wire in the case of FIG. 7 (a), the overall energization loss is reduced to about one third of that in FIG. 1 (a), and it is a low loss wire.

In the structure of the single-core superconducting wire 1, for example, copper, aluminum, silver or the like can be used as the low resistance material, and pure iron or the like can be used as the material of the barrier layer and the low resistance material. For example, Nb, stainless steel, CuNi, Ta or the like can be used as a barrier layer or a high resistance sheath, and MgB ₂ , Bi-based oxide, Y-based oxide, rare earth-based oxide, or the like can be used as a superconductor. Can be used. The single-core superconducting wire 1 can be applied to a coil wound around a stator of a superconducting rotating machine such as a superconducting motor or a superconducting generator, a superconducting current lead, or the like.

  The case where the single core superconducting wire 1 is applied to a superconducting rotating machine will be described below.

  The single-core superconducting wire 1 can be used as a coil that is housed and wound in a recess in the iron core of a stator of a superconducting rotating machine. FIG. 9 is a schematic diagram when the single-core superconducting wire 1 is used as a stator coil of a superconducting motor. FIG. 9A is a schematic diagram of the entire stator, and FIG. 9B is a partially enlarged view of the stator.

  Although a superconducting motor will be described here, it can also be used for a superconducting generator with the same configuration.

In the figure, a, b, and c indicate the a-phase, b-phase, and c-phase, respectively, and the sign indicates the direction of current. Each core slot contains two coils with different phases (the number of turns of each coil is arbitrary, for example, three coils are wound in one slot), and the sum of their currents The net current applied is equal to the current of the remaining phase in the opposite direction, since i _a + i _b + i _c = 0 (i _a , i _b , i _c are three-phase alternating currents that are offset by 120 degrees). That is, i _a + i _b = −i _c .

Winding of the coil, for example, as shown in FIG. _{9 (b), + a 11} 1 pieces of single core superconducting wire 1 housed through is accommodated through -a _12, it fixed number of When wound with the number of turns (for example, the number of turns designed in advance among 1 to 10 turns), the single-core superconducting wire 1 accommodated through + a ₂₁ is accommodated through -a _22. If it is wound with a fixed number of turns, then the single core superconducting wire 1 stored through + a ₃₁ is stored through -a ₃₂ , which is the fixed number of turns. It is wound with. The single-core superconducting wire 1 is wound as described above in the other slots of ± a, ± b, and ± c to form a stator of the superconducting motor. The rotor may have a generally known configuration capable of obtaining torque with respect to the stator, and detailed description thereof is omitted here. The rotor does not necessarily need to use a superconductor, and may be a copper wire, aluminum, a permanent magnet, or the like.

  In general, the stator winding of an all superconducting motor uses a magnetic field generated above the saturation magnetic field of the iron core (up to about 2T), so it is not housed in the recess in the iron core and is mainly composed of an external magnetic field. However, in the case of this embodiment, an iron core is used, a coil is formed with the single-core superconducting wire 1, and it accommodates in the recessed part in an iron core. That is, the external magnetic field generated by the stator coil passes through the iron core having a high magnetic permeability, so that the rotor can be rotated mainly by the self magnetic field. Therefore, it is very effective to use, as a coil, a superconducting wire that can reduce AC loss mainly using a self-magnetic field such as the single-core superconducting wire 1 according to this embodiment.

Thus, by using the single-core superconducting wire 1 as a coil that is housed and wound in the recess in the iron core of the stator of the superconducting rotating machine, a highly efficient superconducting rotating machine with reduced AC loss is obtained. Can be realized. Further, since the AC loss can be reduced, the coil can be made thin, and the superconducting rotating machine can be miniaturized. Further, by thinning the coil, it is possible to ensure a large distance d ₂ between the recesses in the iron core of the stator (by reducing d ₁ in FIG. 9B, d ₁ and d ₂ The ratio can be increased), and a high-performance rotating machine can be realized by increasing the gap magnetic field. Furthermore, if the target to be transferred is liquid hydrogen, the liquid hydrogen to be transferred itself acts as a refrigerant, so there is no need to consider the cooling penalty, and it is much lower power consumption than existing normal motors. The pump can be driven.

  Although the present invention has been described with the above embodiment, the technical scope of the present invention is not limited to the scope described in the embodiment, and various modifications or improvements can be added to this embodiment.

1 Single-core superconducting wire 2 Stabilization layer 3 Superconducting layer 4 Barrier layer 5 High resistance sheath layer

Claims (5)

  A stabilizing layer made of a low resistance material is arranged inside the superconducting wire having a circular cross section, and a superconducting layer made of a superconductor is arranged outside the stabilizing layer. A single-core superconducting wire, wherein the superconductor is continuously formed in a circumferential direction in a cross section perpendicular to the direction. In the single-core superconducting wire according to claim 1,
The low resistance material is copper (Cu), the superconductor is magnesium diboride (MgB ₂ ),
A single-core superconducting wire comprising a barrier layer for preventing a reaction between the copper and magnesium diboride between the stabilizing layer and the superconducting layer. In the single-core superconducting wire according to claim 1,
A single-core superconducting wire, wherein the low-resistance material is pure iron. In the single-core superconducting wire according to any one of claims 1 to 3,
A single-core superconducting wire, wherein a high-resistance sheath is disposed outside the superconducting layer.   The single-core superconducting wire according to any one of claims 1 to 4, wherein the single-core superconducting wire is a coil that is housed and wound in a recess in an iron core of a stator of a superconducting rotating machine. .