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ABSTRACT: We designed and fabricated a 7.5 kW-360 rpm synchronous motor with a superconducting rotor. The rotor was 6-pole type and has no iron core. The armature winding was wound with copper wires. 6 pieces of racetrack-shaped field coils were wound with 5 mm wide RE<sub>1</sub>Ba<sub>2</sub>Cu<sub>3</sub>O<sub>7-delta</sub> (REBCO, RE:Rare Earth) superconducting tapes produced by an ion beam assisted deposition method and a pulsed laser deposition method. The total length of REBCO tape was 400 m per a field coil. We confirmed the good transport properties of the respective field coils up to 80 A at 40 to 50 K before and also after the assembly to a motor. The maximum magnetic field in the field coils was 0.67 T. The superconducting rotor was cooled down to around 40 K by forced-flowed helium gas and the completed motor was tested in a similar way to conventional motors. As a result of a load test, the designed operation of 7.5 kW at 360 rpm was verified for the rated field current of 60 A. Even when the field current was increased up to 70 A at 40 K, the temperature at each part of the superconducting rotor was held constant and the quite stable operation up to 11 kW at 360 rpm was also achieved.
IEEE Transactions on Appiled Superconductivity 07/2009; · 1.04 Impact Factor
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ABSTRACT: We are developing a 7.5 kW-360 rpm synchronous motor with a superconducting rotor. The rotor is 6-pole type and has no iron core. The armature winding is wound with copper. The designed operating temperature is 40 K. It will be cooled by forced-flowed helium gas. We have finished the winding of the first superconducting field coil with YBCO superconducting tapes fabricated by IBAD-PLD method. It is a 62-layer solenoidal coil. The total length of YBCO tape is 400 m. The magnetic field in the field winding is about 0.4 T at maximum and that in the gap is 0.2 T. We cooled it down to 20 K by G-M type cryocooler and investigate the transport properties in advance of the winding of the other field coils. We verified the stable operation up to 100 A at 40 K against the rated current of 50 A. In addition we prepared the cryogenic rotor system and installed 6 pieces of dummy copper coils instead of superconducting coils. We cooled it down to 30 K by forced-flowing helium gas and tested it by rotating up to 360 rpm. We verified the satisfactory good mechanical and thermal operation.
IEEE Transactions on Appiled Superconductivity 07/2008; · 1.04 Impact Factor
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ABSTRACT: We developed a 15 kW synchronous motor with a fixed superconducting field winding. It was 8-pole type. Each field coil was a racetrack-shaped single pancake wound with a YBCO superconducting tape. It was fabricated by IBAD-PLD method and 10 mm in width. The rotating armature was composed of a copper winding and an iron core. The field coils were conduction-cooled down to 20 to 30 K through a copper pipe attached to the copper coil flange, in which helium gas was forced-flowed. The completed motor was first tested in the Suzuka factory of Japan motor and Generator Co. Ltd. before shipping as usual. Then it was moved to the test site of the Nagasaki shipyard of Mitsubishi Heavy Industry Ltd. and installed into a ship propulsion test system, which had a propeller with a diameter of 0.5 m. We verified the quite stable underwater operation and the output power of 15 kW-360 rpm as designed.
IEEE Transactions on Appiled Superconductivity 07/2007; · 1.04 Impact Factor
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H. Kamijo,
H. Hata,
H. Fujimoto,
A. Inoue,
K. Nagashima,
K. Ikeda,
M. Iwakuma,
K. Funaki,
Y. Sanuki, A. Tomioka,
H. Yamada,
K. Uwamori,
S. Yoshida
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ABSTRACT: We have been developing a lightweight and high-efficiency superconducting traction transformer for railway rolling stock. We designed and fabricated a prototype superconducting traction transformer of a floor-mount type for Shinkansen rolling stock. In this study, we present test results such as type test, system test and vibration test. We performed the type test in accordance with JIS, E5007. In this test, we measured the basic electrical characteristics. In the system test, we tested the transformer with a dynamic simulator for rolling stock, as a converter connected at secondary winding, and verified the operating characteristics. We performed vibration tests in accordance with JIS, E4031, vibrating the transformer on a shaking table with three-dimensional movement. As a result, we could verify that the transformer satisfied the requirement almost exactly as initially planned.
IEEE Transactions on Appiled Superconductivity 07/2007; · 1.04 Impact Factor
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H Kamijo,
H Hata,
H Fujimoto,
A Inoue,
K Nagashima,
K Ikeda,
H Yamada,
Y Sanuki, A Tomioka,
K Uwamori,
S Yoshida,
M Iwakuma,
K Funaki
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ABSTRACT: We designed a floor type single-phase 4 MVA superconducting traction transformer for Shinkansen rolling stock. In this study, we fabricated a prototype superconducting traction transformer based on this design. This transformer of the core-type design has a primary winding, four secondary windings and a tertiary winding. The windings are wound by Bi2223 superconducting tapes and cooled by subcooled liquid nitrogen. The core is kept at room temperature. The cryostat is made of GFRP with two holes to pass core legs through. The outer dimensions are about 1.2m × 0.7m × 1.9m excluding the compressor. Its weight is 1.71t excluding that of refrigerator and compressor. The transformer was tested according to Japanese Industrial Standards (JIS)-E5007. We confirmed that the performance of transformer has been achieved almost exactly as planned. The rated capacity is equivalent to 3.5MVA in the superconducting state.
Journal of Physics Conference Series 07/2006; 43(1):841.
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ABSTRACT: We fabricated a cryocooler-cooled Bi2223 superconducting pulsed coil and experimentally studied the thermal runaway in dc or ac operation. We carried out numerical simulation of thermal properties of the coil in order to explain the thermal runaway of the coil. Firstly, we analyzed the total heat generation of flux-flow losses and ac losses inside the winding from the experimental results of the external field losses and the E-J characteristics for the Bi2223 strands. Secondly, we numerically simulated the thermal properties by using a 2-dimensional heat conduction equation with axial symmetry. The numerical simulation shows the relation between the initiation of thermal runaway and the temperature distribution with highly concentrated heat source in the winding. We have a semi-quantitative agreement between the numerical results and the experimental ones for the condition of the thermal runaway
IEEE Transactions on Appiled Superconductivity 07/2006; · 1.04 Impact Factor
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ABSTRACT: We studied the thermal and electromagnetic behavior of a conduction-cooled superconducting pulse coil. It was wound with a 4-strand parallel conductor composed of silver sheathed Bi2223 multifilamentary tapes and impregnated with an epoxy resin. We first investigated the temperature dependence of the thermal runaway current in dc operation. It was higher than the critical current by several tens amps at any temperature from 40 to 90 K. In order to study the mechanism of the thermal runaway, we carried out the numerical simulation of the coil behavior. We found out that the thermal runaway was caused when the heat generation at the winding end close to the cryocooler head where the flux-flow loss is the largest due to perpendicular magnetic field exceeded the cooling through thermal diffusion though the thermal runaway of the coil started at the other end of the winding. If the transport current is smaller than the thermal runaway current at the coil temperature just after applying current, the temperature distribution in the longitudinal direction of the coil varied into a monotonous gradient and the steady thermal flow was established. After that the coil temperature decreased to the balanced one
IEEE Transactions on Appiled Superconductivity 07/2006; · 1.04 Impact Factor
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ABSTRACT: We designed and fabricated a 1 T cryocooler-cooled oxide superconducting pulsed coil with Bi2223 multifilamentary flat wires. Previously we studied temperature dependence of the thermal runaway current of the pulsed coil in dc operation. The thermal runaway current was higher than the critical current that was defined as the current where the electric field 10<sup>-4</sup> V/m was generated on average over the whole length of the conductor. In this paper, we studied the coil temperature and the ac loss dependence of the thermal runaway current in ac operation. We operated the coil at 0.5 to 5 Hz with a sinusoidal-waveform transport current. The initial coil temperature was set between 30 and 100 K. The thermal runaway current decreased monotonically with increasing temperature in a similar way to dc operation. However, in a low temperature region, the thermal runaway current was restricted to a lower level than that in dc operation due to the ac loss. We discuss the frequency dependence of thermal runaway current in ac operation.
IEEE Transactions on Appiled Superconductivity 07/2005; · 1.04 Impact Factor
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ABSTRACT: We fabricated a 1 T cryocooler-cooled oxide superconducting pulsed coil. It is a 16-layer solenoidal coil wound with an interlayer-transposed 4-strand parallel conductor composed of Bi-2223 multifilamentary flat wires. The insulated strands were transposed only between layers to make all strands inductively equivalent. To suppress the temperature rise due to the AC loss, the aluminum nitride (AlN) plates were arranged between layers as heat drains. The pulsed coil was cooled down to 30 K by a single stage cryocooler. It can be operated continuously at 40 K in the 1 T triangular wave operation at 1 Hz. First we studied the temperature dependence of thermal runaway current of the coil under the application of direct transport current. The runaway current was higher than the critical current, which was defined as the current where the electric field of 10<sup>minus;4</sup> V/m was generated on average over the whole length of the conductor. Next we studied the temperature variation of the coil in a sinusoidal operation of 1 Hz. The temperature increment was much more gradual than that in the DC operation. In this paper, we discuss the thermal properties of the cryocooler-cooled oxide superconducting pulsed coil, taking into account the heat generation of AC loss and flux-flow loss and the cooling capacity of a cryocooler.
IEEE Transactions on Appiled Superconductivity 07/2004; · 1.04 Impact Factor
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H. Hayashi,
H. Kimura,
Y. Hatabe,
K. Tsutsumi, A. Tomioka,
T. Bohno,
S. Nose,
Y. Yagi,
T. Ishii,
M. Iwakuma,
K. Funaki
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ABSTRACT: We designed and fabricated a 4 kJ conduction-cooled high-Tc superconducting (HTS) pulse coil. The coil is wound with an interlayer-transposed 6-strand parallel conductor which is composed of Bi-2223 silver alloy-sheathed multi-filamentary wires. We had developed a complete 3.6 MJ/1 MW low-Tc superconducting (LTS) SMES system for testing on a power line at Imajuku substation. Aiming at the feasible operation of SMES applying a HTS coil, we made a SMES system set-up in which HTS coils were serially connected to 3 LTS coils of the SMES. The SMES including the HTS coil was connected to Imajuku substation's power system, to made operational tests of compensation for load fluctuation at the 6 kV power line. The test results lead to the feasibility of the HTS SMES for practical use in future power systems.
IEEE Transactions on Appiled Superconductivity 07/2003; · 1.04 Impact Factor
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M. Iwakuma,
H. Miyazaki,
Y. Fukuda,
K. Kajikawa,
K. Funaki,
K. Tsutsumi,
H. Hayashi,
H. Kimura, A. Tomioka,
T. Bohno,
Y. Yagi
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ABSTRACT: We designed and fabricated a 4 kJ conduction-cooled superconducting pulse coil with a 6-strand interlayer-transposed parallel conductor composed of Bi2223 multifilamentary tapes. We adopted the helium gas forced-flow cooling system where the helium gas flowed inside a copper pipe soldered with the flanges of brass. We succeeded in the continuous pulse operation with an amplitude of 500 A-1.6 T at a sweep rate of 140 A/s at 30 K as designed. Even in the ac operation with an ac loss of 120 W, the difference in temperature inside the winding was only 5 K and it was possible to hold the coil temperature around 30 K. In this paper, we report the design and the test results of the coil system from the aspect of ac loss and thermal properties.
IEEE Transactions on Appiled Superconductivity 07/2003; · 1.04 Impact Factor
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M. Iwakuma,
K. Funaki,
K. Kajikawa,
H. Tanaka,
T. Bohno, A. Tomioka,
H. Yamada,
S. Nose,
M. Konno,
Y. Yagi,
H. Maruyama,
T. Ogata,
S. Yoshida,
K. Ohashi,
K. Tsutsumi,
K. Honda
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ABSTRACT: We designed and built a single-phase 1 MVA-22/6.9 kV HTS
transformer with the multi-layered cylindrical windings composed of
Bi2223 parallel conductors. In advance of the design, the AC loss
induced in the windings was estimated on the basis of the observed
results in a strand. A subcooled liquid nitrogen cryogenic system with
the corresponding cooling capacity was developed and attached to the
transformer. The actual AC loss was measured by an electrical method. It
was a great part of the total heat load and dominated the temperature
rise of subcooled liquid nitrogen. We discussed the validity of the
present estimation procedure of the AC loss in the windings as compared
with the observed results
IEEE Transactions on Appiled Superconductivity 04/2001; · 1.04 Impact Factor
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ABSTRACT: A 60 kA HTS current lead has been designed for large fusion
magnets such as the ITER magnet. The actual refrigeration input power
required to cool the current lead is specified to be reduced to one
third that of the conventional copper lead. The HTS part of the 60 kA
lead consists of 48 units installed with cylindrical array into the
outer surface of a stainless steel tube with a diameter of 146 mm. Each
unit is composed of six Bi2223/Ag-10at%Au tapes, and its cross-sectional
dimension is 6.5 mm×2.7 mm. The HTS part is cooled by conduction,
and the warm and cold end temperature conditions of the HTS part are 50
K and 4.5 K, respectively. The copper part is cooled by helium gas, a
flow rate of 3.9 g/s and the inlet temperature of 35 K. The 60-kA lead
has been designed in consideration of safety under the long discharge
time condition of ITER-TF coil with a detection time of 2 sec, and a
discharge time constant of 15 sec. For the purpose of verifying the
reliability of the design for the long discharge time, one unit sample
has been fabricated and tested. The result indicates that the maximum
temperature rise of the HTS part is less than 150 K for the ITER
like-discharge from 1.25 kA corresponding to 60 kA of the full lead with
48 units
IEEE Transactions on Appiled Superconductivity 04/2001; · 1.04 Impact Factor
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ABSTRACT: We made a preliminary investigation of the applicability of high-T
<sub>c</sub> superconducting parallel conductors to pancake coils. For
the sake of a uniform current distribution and low AC loss, the
constituent strands need to be transposed so as to be inductively
equivalent with each other. We adopted an interdisk transposition where
the strands are not transposed inside a single-pancake coil but only at
the joint between the pancake coils. The fabrication process is simple.
We have only to fabricate the same double-pancake coils and connect the
strands individually with transposition outside the winding. We searched
theoretically for the optimum transposition in the case of 3-strand and
verified the theoretical result by using small test coils wound with
NbTi 3-strand parallel conductors for convenience
IEEE Transactions on Appiled Superconductivity 04/2000; · 1.04 Impact Factor
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ABSTRACT: The authors designed and fabricated a 1 T cryocooler-cooled pulse
coil operating at 40 K. A 4-strand interlayer-transposed parallel
conductor composed of Bi-2223 rectangular cross-sectional
multifilamentary wires was adopted to realize a uniform current
distribution and to reduce the AC loss density down to the level of that
of a single strand. The pulse coil is a 16-layer solenoidal one with an
inner diameter of 52 mm, an outer diameter of 111 mm and a height of 120
mm. The heat drains of AlN plates, which are insulators, are arranged
between layers for the cooling of the heat due to the AC loss by heat
conduction. They could continuously operate the coil in a triangular
waveform mode with an amplitude of 1 T and a frequency of 1 Hz. The AC
loss was 10.6 W and the other thermal load was 13 W
IEEE Transactions on Appiled Superconductivity 07/1999; · 1.04 Impact Factor
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ABSTRACT: The authors have been developing high-Tc superconducting coils for
SMES applications. Their primary goal is to make a HTS coil which is
cooled to 40 K by a single-stage cryocooler and continuously operated at
1 Hz with a field amplitude of 1 T. The coil has heat drains of AlN
plates to remove heat because of AC losses. They made a cooling model
coil system to study the effective arrangement of the heat drains. The
system consisted of a model coil using Cu conductors, current leads and
a cryocooled system. The test coil was divided into three sections in
different arrangement of heat drains. The model coil was daubed with a
high thermal conductivity epoxy resin to improve thermal contact
resistance between the conductors and AlN plates. They tested the coil
by Joule heating which was equal to AC losses. They measured the
temperature distribution in the coil and the temperature difference
between Cu conductors and AlN plates. The temperature difference was
measured between 0.2 K and 0.7 K. The results will be applied to the 1 T
HTS coil design
IEEE Transactions on Appiled Superconductivity 07/1999; · 1.04 Impact Factor
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ABSTRACT: High temperature superconductor (HTS) current leads have been
developed for the International Thermonuclear Experimental Reactor
(ITER) magnet system, which are required not only to reduce the lead
heat leak but also to maintain safety in a fault condition. A pair of
10-kA class HTS current leads was fabricated and tested. The lead
consists of a copper part and an HTS part. The HTS part is composed of
192 Bi-2223 silver-alloy sheathed tapes in a cylindrical array on a
stainless steel tube. Thermal performance and stability were tested. The
current leads could carry up to 14.5 kA by placing magnetic materials
between the HTS elements, which were installed to reduce the
perpendicular magnetic field in the HTS elements
IEEE Transactions on Appiled Superconductivity 07/1999; · 1.04 Impact Factor
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ABSTRACT: We have been developing high-temperature superconducting (HTS)
current leads for a 1 kWh/1 MW module-type SMEs. Each module of a
module-type SMES requires a pair of current leads. Therefore, we
employed bulk HTS in order to reduce the heat load of the current leads.
It is important that HTS current leads for SMES be reliable. The HTS
current leads described in this paper have been designed to minimize the
heat load and to maintain a high level of reliability. The HTS current
leads are designed to hold the heat load at the cold-end terminal to
less than 0.1 W. They are also designed with safety leads to bypass
current in the event the HTS is quenched and with metal superconductors
to assure the continuation of SMES operation even if the HTS should fail
or deteriorate in performance. This paper describes an optimal design
and the results of a heat load evaluation of HTS current leads for SMES
IEEE Transactions on Appiled Superconductivity 07/1997; · 1.04 Impact Factor
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ABSTRACT: For pt.I see ibid., vol.7, no.2, p.684-7 (1997). We have been
developing HTS current leads for a 1 kWh/1 MW module type SMES system
(which we call “ESK” for Experimental SMES of Kyushu
Electric Power Co., Inc.). Each module of a module type SMES system has
a pair of current leads. For the purpose of reducing the heat load from
the current leads, we have employed a bulk HTS. As a step in the
preparation of HTS current leads for ESK, we trial produced HTS current
leads and tested them to evaluate their characteristics. Our test
results indicated that the heat load in a steady state at a rated
current of 1 kA and with a rated flow rate of 0.05 g/s was 0.035 W, well
below the specified value of 0.1 W. Also, our results indicated that the
HTS current leads can be satisfactorily energized for pulsing operation
at a rated current for ESK of 500 A-1 kA. The heat load under such
conditions was 0.025 W, approximately 80% of that under normal 1 kA
operating conditions. It was also verified that operation could be
continued for 15 minutes even when the coolant flow was stopped
IEEE Transactions on Appiled Superconductivity 07/1997; · 1.04 Impact Factor
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A. Tomioka,
T. Otonari,
T. Ogata,
M. Iwakuma,
H. Okamoto,
H. Hayashi,
Y. Iijima,
T. Saito,
Y. Gosho,
K. Tanabe,
T. Izumi,
Y. Shiohara
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ABSTRACT: We are developing an elemental technology for 66 kV/6.9 kV 20 MVA-class power transformer with YBCO conductors. The protection of short-circuit technology is one of the elemental technologies for HTS transformer. Since short-circuit current is much higher than critical current of YBCO tape, there is a possibility that superconducting characteristics may be damaged during short-circuit period. We made a conductor to compose the YBCO tape with copper tape. We manufactured 6.9 kV/2.3 kV 400 kVA-class YBCO model transformer using this conductor and performed short-circuit current test. The short-circuit current of primary winding was 346 A which was about six times larger than the rated current. The I–V characteristics of the winding did not change before and after the test. We may consider this conductor withstands short-circuit current.Highlights► The 6.9 kV/2.3 kV 400 kVA-class single-phase YBCO model transformer with the YBCO tape with copper tape was manufactured for short-circuit current test. ► Short-circuit test was performed and the short-circuit current of primary winding was 346 A which was about six times larger than the rated current. ► The I–V characteristics of the winding did not change before and after the test. ► The transformer withstood short-circuit current. ► We are planning to turn the result into a consideration of a 66 kV/6.9 kV-20 MVA-class three-phase superconducting transformer.
Physica C Superconductivity 471:1374-1378. · 1.01 Impact Factor
