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(a) The relationship between the voltage drop for the HTS winding and RTC including copper electrodes under the applied current and magnetic field of 5 T. (b) The temperature variation of the test RTC during the current flow in a 5 T magnetic field.
Source publication
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We report a field-pole high-temperature superconductor (HTS) magnet designed for 1 MW-class motor for propulsion. The field pole is assembled to the rotor of the radial-type motor. Each field pole is composed of HTS-Bi2223 tape wound into coils which have been piled up as a double pancake coils. In the design concept of the motor, we employ field p...
Contexts in source publication
Context 1
... these results, we can see that it is possible and safe to apply a 150 A current to the coil at 30 K, for getting enough power. The same cooling and voltage-characterization study was then conducted on the test RTC under 5 T. The experimental geometry and the positions of the sensors are the same as in the study under 4 T shown in the figure 3. Figure 6 (a) shows the relationship between the voltage of terminals and the applied current under a magnetic field of 5 T. Figure 6 (b) shows the temperature variation during the current flow. ...
Context 2
... these results, we can see that it is possible and safe to apply a 150 A current to the coil at 30 K, for getting enough power. The same cooling and voltage-characterization study was then conducted on the test RTC under 5 T. The experimental geometry and the positions of the sensors are the same as in the study under 4 T shown in the figure 3. Figure 6 (a) shows the relationship between the voltage of terminals and the applied current under a magnetic field of 5 T. Figure 6 (b) shows the temperature variation during the current flow. ...
Citations
... It is known that an applied magnetic field perpendicular to the HTS tape drastically decreases the critical current compared to a parallel field. In our previous study, the field-angle dependence of the critical current density in the Bi2223 HTS tape surface was studied intensively with prototype windings [11]. According to the results, we have calculated the electric power loss of the HTS winding under practical motor operation conditions. ...
Efforts on the generation of intensified magnetic flux have been made for the optimized shape of HTS winding applications. This contributes to the high efficiency of the rotating machines using HTS windings. Heat generation from the HTS windings requires to be suppressed as much as possible, when those coils are under operation with either direct or alternative currents. Presently, the reduction of such thermal loss generated by the applied currents on the HTS coils is reported with a magnetic flux deflection system. The HTS coils are fixed together with flattened magnetic materials to realize a kind of redirection of the flux pathway. Eventually, the magnetic flux density perpendicular to the tape surface (equivalent to the a-b plane) of the HTS tape materials is reduced to the proximity of the HTS coil. To verify the new geometry of the surroundings of the HTS coils with magnetic materials, a comparative study of the DC coil voltage was done for different applied currents in prototype field-pole coils of a ship propulsion motor. (C) 2012 Published by Elsevier B.V. Selection and/or peer-review under responsibility of the Guest Editors.
... From these results, under 2-2.5Tesla of estimated maximum lateral magnetic field subjected to the stack of coils, the critical current for the whole field-pole HTS coils can be expected to be larger than 200A of the design operating current. In this paper, we defined the critical current is the average voltage drop with 1 µV/cm whole HTS winding because the voltage rise around critical current is very large at 30K and HTS wire length is short (32 m) [3]. In near future, we will develop the estimation method of critical current, n-value and heat generation from the stack of coils under the practical multi-directional magnetic fields. ...
To reduce fuel consumption and lead to a major reduction of pollution from NOx, SOx and CO2, the electric ship propulsion system is one of the most prospective substitutes for conventional ship propulsion systems. In order to spread it, innovative technologies for the improvement of the power transmission are required. The high temperature superconducting technology has the possibility for a drastic reduction of power transmission loss. Recently, electric podded propulsions have become popular for large cruise vessels, icebreakers and chemical tankers because of the flexibility of the equipment arrangement and the stern hull design, and better maneuverability in harbour, etc. In this paper, a 1 MW-class High temperature superconducting (HTS) motor with high efficiency, smaller size and simple structure, which is designed and manufactured for podded propulsion, is reported. For the case of a coastal ship driven by the optimized podded propulsion in which the 1MW HTS motor is equipped, the reductions of fluid dynamic resistance and power transmission losses are demonstrated. The present research & development has been supported by the New Energy and Industrial Technology Development Organization (NEDO).
Energy and environment have been extremely highlighted, since we are obliged to challenge to sustain the development of a world community against climate change. Rotating machinery provides motors or generators for use in power bases, various industries, transportation mobility in logistics. The growing population and economy make it necessary to eliminate the dependence on fossil fuels. Our team has engaged in the intensive study of superconducting rotating machinery under industry-academia collaborations. In the course of our works, the team studied the field poles and the ship propulsion motor by using 1G HTS wire. Separately, we have conducted a successive study to prove the viability of a machine with field poles composed of Gd-123 HTS bulks. Both the design and construction were carried out in TUMSAT. The machines have been studied for durability and survivability. We provide a brief review of the publicized studies of us on the HTS rotating machinery and try to concrete a potential application of HTS rotating machinery to ship propulsion and renewable energy such as marine current turbines. The concept may contribute to improving the local power supply sources on the coast and islands by reducing the environmental damage.
Intensified magnetic flux generated by high-temperature superconducting (HTS) windings makes feasible the industrial rotating machines with both high efficiency and high torque density. For those HTS windings, the superconducting characteristics are influenced by the magnetic flux interacting with the HTS tape. Especially, the magnetic flux perpendicular to the a-b plane of the HTS tape decreases the critical current property, according to the anisotropy of 1G/2 G HTS tape conductors. This leads to the drop of the operating current limit as well as a heat loss in the windings. To avoid these losses as much as possible, the magnetic flux deflection (MFD) was studied. In a previous study, the advantage to suppress the heat loss in the wire was verified on Bi2223 prototype windings by adopting MFD composed of flattened magnetic materials. To evaluate the effect of adopting flux deflection to industrial HTS rotating machines such as MW class industrial motors, we conducted the study by using a middle-scale field pole model stacked with HTS windings composed of 4 race-track double-pancake coils. We examined the effect of deflected flux on the winding at 30 K, which was the operating temperature of the field pole magnet. The reduction of the thermal loss was successfully confirmed by using MFD. The present study exhibits the importance of a flux deflection on the field pole magnet in the power applications.
We are currently under development of a 1 MW-class HTS ship propulsion motor, for which rotating HTS coil made of Bi-2223 tape wire has already been successfully cooled down to 30 K and attained the target performance. There, the electric loss estimation in the HTS tape wire is required under practical operation conditions. The magnetic field angle dependency on I<sub>C</sub>-B characteristics of Bi-2223 used for the field winding was measured at 40 K. Furthermore, the interlinkage flux density on HTS coils in the horizontal and vertical directions were calculated using three-dimensional magnetic field simulations. It was found that the estimated electric loss of the entire HTS coil using these measured and simulated results was about 9 W at the operating field current of 200 A, which was considerably small compared with 30 W at 215 A, and that the operating field current of 200 A was appropriate and desirable considering the required refrigerator capacity.
