Kitano Seiki Co.

Tokyo, Japan

Kitano Seiki Co.

Tokyo, Japan
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Miki M.,Tokyo University of Marine Science and Technology | Miki M.,Kitano Seiki Co. | Felder B.,Tokyo University of Marine Science and Technology | Tsuzuki K.,Tokyo University of Marine Science and Technology | And 6 more authors.
Superconductor Science and Technology | Year: 2010

We report a refrigeration system for rotating machines associated with the enhancement of the trapped magnetic flux of bulk high-temperature superconductor (HTS) field poles. A novel cryogenic system was designed and fabricated. It is composed of a low-loss rotary joint connecting the rotor and a closed-cycle thermosiphon under a GM cryocooler using a refrigerant. Condensed neon gas was adopted as a suitable cryogen for the operation of HTS rotating machines with field poles composed of RE-Ba-Cu-O family materials, where RE is a rare-earth metal. Regarding the materials processing of the bulks HTS, thanks to the addition of magnetic particles to GdBa2Cu3O7-d (Gd123) bulk superconductors an increase of more than 20% in the trapped magnetic flux density was achieved at liquid nitrogen temperature. Field-pole Gd123 bulks up to 46 mm in diameter were synthesized with the addition of Fe-B alloy magnetic particles and assembled into the synchronous machine rotor to be tested. Successful cooling of the magnetized rotor field poles down to 35 K and low-output-power rotating operation was achieved up to 720 rpm in the test machine with eight field-pole bulks. The present results show a substantial basis for making a prototype system of rotating machinery of applied HTS bulks. © 2010 IOP Publishing Ltd.


Zhou D.,Tokyo University of Marine Science and Technology | Izumi M.,Tokyo University of Marine Science and Technology | Miki M.,Tokyo University of Marine Science and Technology | Felder B.,Tokyo University of Marine Science and Technology | And 2 more authors.
Superconductor Science and Technology | Year: 2012

The paper contains a review of recent advancements in rotating machines with bulk high-temperature superconductors (HTS). The high critical current density of bulk HTS enables us to design rotating machines with a compact configuration in a practical scheme. The development of an axial-gap-type trapped flux synchronous rotating machine together with the systematic research works at the Tokyo University of Marine Science and Technology since 2001 are briefly introduced. Developments in bulk HTS rotating machines in other research groups are also summarized. The key issues of bulk HTS machines, including material progress of bulk HTS, insitu magnetization, and cooling together with AC loss at low-temperature operation are discussed. © 2012 IOP Publishing Ltd.


Miki M.,Tokyo University of Marine Science and Technology | Felder B.,Tokyo University of Marine Science and Technology | Tsuzuki K.,Tokyo University of Marine Science and Technology | Deng Z.,Tokyo University of Marine Science and Technology | And 4 more authors.
IEEE Transactions on Applied Superconductivity | Year: 2011

A synchronous rotation study with eight field rotor pole of Gd123 bulks was performed with the axial-type motor. The field pole of Gd123 packs with and without doped amorphous magnetic particles Fe-B-Si-Nb-Cr-Cu (MP) were employed. Before and after the synchronous operation, the change of the trapped magnetic flux on the bulk was investigated at the operating temperature of 40 K. The observed decay of the trapped integrated flux on the surface of Gd123 packs after 5 hours synchronous rotation were 7.2% for the Gd123 pack without MP doping and 4.1% for the Gd123 bulk doped with MP. The present result indicates that the lowering operation temperature may be beneficial to avoid the AC loss. This also leads to another complementally conclusion that the employment of the condensed neon gas cooling system is a suitable choice from the viewpoint of practical applications of the HTS bulks in contrast to liquid nitrogen cooling. In addition, the Gd123 doped with MP alloy particles provide a practical magnetic flux trapping function at 40 K. © 2010 IEEE.


Felder B.,Tokyo University of Marine Science and Technology | Miki M.,Tokyo University of Marine Science and Technology | Deng Z.,Tokyo University of Marine Science and Technology | Tsuzuki K.,Tokyo University of Marine Science and Technology | And 3 more authors.
IEEE Transactions on Applied Superconductivity | Year: 2011

Temperature Superconductors (HTS) applied to rotating machines require an efficient cooling system. It is necessary to increase the maximum trapped flux density in the bulk HTS magnets and decrease the overall cooling time. In this paper, we added a gaseous helium phase to a condensed-neon closed-cycle thermosyphon. The latent heat of neon-film cooling is combined with helium's high thermal conductivity. Different mixture proportions were evaluated in terms of resistance to variable heat loads. More helium decreased the temperature variation of the evaporator. The mixture was then used to cool down a 30 kW-grade gadolinium-bulk HTS synchronous motor. The eight bulk HTS conductors of the rotor were cooled to 40 K in less than six hours. The application of this thermosyphon is envisioned for larger rotating machines. © 2011 IEEE.


Felder B.,Tokyo University of Marine Science and Technology | Miki M.,Tokyo University of Marine Science and Technology | Tsuzuki K.,Tokyo University of Marine Science and Technology | Izumi M.,Tokyo University of Marine Science and Technology | Hayakawa H.,Kitano Seiki Co.
Journal of Physics: Conference Series | Year: 2010

The axial-gap synchronous machine developed in our laboratory is based on Gd-bulk HTS field-pole magnets, able to trap a part of the magnetic flux they are submitted to when cooled down below T c. At the liquid nitrogen temperature, by the Pulsed-Field Magnetization (PFM), 1.04 T was trapped in 60 mm-diameter and 20 mm-thickness magnets, leading to an output power of the motor of 10 kW at 720 rpm. To enhance this performance, we have to increase the total amount of trapped flux in the bulk, the shortest way being to decrease the temperature of the bulk HTS. Thus, we focused on the improvement of the condensed-neon cooling system, a closed-cycle thermosyphon, so that it provided enough cooling power to lead the rotor plate enclosing the magnets to a low temperature. The present study implied coming out with a new fin-oriented design of the condensation chamber; hence, the numeric calculations and FEM software (ANSYS) heat transfer simulations were conducted for various shapes and positions of the fins. The trapezoidal design offering the best efficiency was then manufactured for testing in a heat-load test configuration, leading to cooling times divided by three and a maximum heat load endured of 55 W. © 2010 IOP Publishing Ltd.


Miki M.,Tokyo University of Marine Science and Technology | Miki M.,Kitano Seiki Co. | Felder B.,Tokyo University of Marine Science and Technology | Tsuzuki K.,Tokyo University of Marine Science and Technology | And 2 more authors.
Journal of Physics: Conference Series | Year: 2010

We have studied a prototype of an axial-gap type synchronous motor with Gd-bulk HTS field-pole magnets since 2001. At the liquid nitrogen temperature, these bulks have trapped over 1 T inside the motor after being applied the pulsed field magnetization method. Increasing the flux of the field poles is the most straightforward way of improving the output power of the motor. Cooling down the bulk HTS magnets below the liquid nitrogen temperature provides an effective alternative to increase the magnetic flux trapping. In 2007, we exchanged the cryogen from liquid nitrogen to condensed neon. The key technology of this challenge is a rotary joint, introducing a fluid cryogen into the rotating body in the motor from the static reservoir. We have successfully developed a compact rotary joint which is smaller and lighter than the existent one (1/10 volume, 1/3 length and 1/12 weight). The present joint was manufactured and evaluated with liquid nitrogen and condensed neon. We presume a total heat loss of this rotary joint of less than 10 watts. Successful cooling and rotating tests of the bulk-HTS motor with this novel rotary joint are conducted. © 2010 IOP Publishing Ltd.


Sato R.,Tokyo University of Marine Science and Technology | Felder B.,Tokyo University of Marine Science and Technology | Miki M.,Tokyo University of Marine Science and Technology | Miki M.,Kitano Seiki Co. | And 3 more authors.
IEEE Transactions on Applied Superconductivity | Year: 2013

Commercial high-temperature superconducting (HTS) wires restrain us to an operation temperature ranging from 20 to 40 K for field-pole magnets applied to rotating machinery. We have proposed to employ a mixture of helium and neon gas in a closed-cycle thermosyphon based on a GM cryo-refrigerator. In this paper, we discuss the temperature stability of the evaporator created by a helium-neon mixture cooling coupled with a closed-cycle thermosyphon, upon an external heat load on a 100-kW-grade HTS synchronous machine. A home-made cooling system, including the condenser, was designed. The evaporator was assembled within the motor in accordance with thermal and mechanical analysis. The cooling of the evaporator with the 100-kW-grade HTS synchronous motor was applied against a variable heat load equivalent with the actual HTS rotor field poles. We report these results and propose its potential application to a large-scale ship propulsion motor. © 2002-2011 IEEE.


Felder B.,Tokyo University of Marine Science and Technology | Miki M.,Tokyo University of Marine Science and Technology | Tsuzuki K.,Tokyo University of Marine Science and Technology | Shinohara N.,Tokyo University of Marine Science and Technology | And 2 more authors.
AIP Conference Proceedings | Year: 2012

The cooling systems used for rotating High-Temperature Superconducting (HTS) machines need a cooling power high enough to ensure a low temperature during various utilization states. Radiation, torque tube or current leads represent hundreds of watts of invasive heat. The architecture also has to allow the rotation of the refrigerant. In this paper, a free-convection thermosyphon using two Gifford-McMahon (GM) cryocoolers is presented. The cryogen is mainly neon but helium can be added for an increase of the heat transfer coefficient. The design of the heat exchangers was first optimized with FEM thermal analysis. After manufacture, they were assembled for preliminary experiments and the necessity of annealing was studied for the copper parts. A single evaporator was installed to evaluate the thermal properties of such a heat syphon. The maximum bearable static heat load was also investigated, but was not reached even at 150 W of load. Finally, this cooling system was tested in the cooling down of a 100-kW range HTS rotating machine containing 12 Bi-2223 double-pancake coils (DPC). © 2012 American Institute of Physics.


Patent
Tokyo University of Marine Science, Technology and Kitano Seiki Co. | Date: 2012-04-11

Problem to be Solved To provide a small, lightweight, cryo-rotary joint. Solution A joint includes a housing 2, a refrigerant tube 3 connected to a refrigerant source and communicated with a target part in a rotating machine, a rotating member 4 loosely fitted inside with the refrigerant tube and fixed to a rotary part of the rotating machine, and a relatively rotating member 5 having a fixed-side member 5a and rotating-side member 5b, wherein the fixed-side member is connected to the refrigerant tube via a refrigerant tube extension section 3a, the rotating-side member is connected to the rotating member via a rotating member extension section 4a, a refrigerant zone is formed by spaces 7 and 8 defined by the refrigerant tube, rotating member, and refrigerant tube and rotating member extension sections, a sealing member 10 is installed between the fixed-side and rotating-side members, and a vacuum chamber and pressure chamber are defined within the housing.


Patent
Kitano Seiki Co., Tokyo University of Marine Science and Technology | Date: 2010-06-02

Problem to be Solved To provide a small, lightweight, cryo-rotary joint. Solution A joint includes a housing 2, a refrigerant tube 3 connected to a refrigerant source and communicated with a target part in a rotating machine, a rotating member 4 loosely fitted inside with the refrigerant tube and fixed to a rotary part of the rotating machine, and a relatively rotating member 5 having a fixed-side member 5a and rotating-side member 5b, wherein the fixed-side member is connected to the refrigerant tube via a refrigerant tube extension section 3a, the rotating-side member is connected to the rotating member via a rotating member extension section 4a, a refrigerant zone is formed by spaces 7 and 8 defined by the refrigerant tube, rotating member, and refrigerant tube and rotating member extension sections, a sealing member 10 is installed between the fixed-side and rotating-side members, and a vacuum chamber and pressure chamber are defined within the housing.

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