Concepts for HTS and MgB2 in Transformers

2006 ◽  
Vol 47 ◽  
pp. 195-203 ◽  
Author(s):  
Pascal Tixador
Keyword(s):  
Low Cost ◽  
Point Of View ◽  
Coated Conductors ◽  
Ac Loss ◽  
Mobile Systems ◽  
Ac Losses ◽  
Magnetic Flux Density ◽  
Price Performance ◽  
Substantial Progress ◽  
Lower Temperature

After the emergence of AC NbTi strands, superconducting transformers were successfully built. But the very high cost of 4 K cryogenics made these transformers economically not attractive. The high Tc superconductors (HTS), operating at much higher temperatures, change these conclusions with low cost HTS conductors. The high cost of PIT tapes and the relatively large AC losses remain issues. The second generation HTS wires, the REBCO coated conductors, are under development and achieved substantial progress recently. They operate at higher temperatures and intrinsically show lower AC losses especially for transformers. MgB2 is the third option. The magnetic flux density conditions make possible the operation at 27 K and they show low costs. This paper provides a preliminary design for an on-board 40 MVA transformer using YBCO coated conductors and MgB2 wires. Both superconducting transformers show similar volume and weight. The power density per unit mass and volume is improved by a factor about two, cryogenic included, compared to resistive systems. This makes them very attractive for on-board mobile systems. The economical point of view will be discussed based on some targets price/performance for superconductors and cryocoolers. MgB2 is penalized by its operation at lower temperature (27 K / 77 K), which makes cryogenics very expensive. The advantage of the low cost of MgB2 compared to REBCO may be lost except with very low AC loss MgB2 tapes.

AC Loss Characteristics of Stacks of YBCO Coated Conductors

2006 ◽  
Vol 946 ◽  
Author(s):  
Francesco Grilli ◽  
Stephen P. Ashworth ◽  
Svetlomir Stavrev
Keyword(s):  
Magnetic Field ◽  
Transport Current ◽  
Point Of View ◽  
Coated Conductors ◽  
Ac Loss ◽  
Ac Losses ◽  
Practical Applications ◽  
Superconducting Coils ◽  
Loss Characteristic ◽  
Ybco Coated Conductors

ABSTRACTPractical applications of YBCO coated conductors (CC) involving superconducting coils will utilize tapes packed together in an arrangement resembling a vertical stack. In such configuration there is an important electromagnetic interaction between the tapes, which strongly influences the loss characteristic of the device.In the presence of an external magnetic field, the losses are reduced compared to an isolated tape because of the reduced aspect ratio of the conductor and, at least for low fields, because of an effective screening of the central part of the stack. On the contrary, in the case of AC transport current, the losses tend to increase due to the enhancement of the local field caused by the interaction of the self-field produced by neighboring tapes. In practical situations the conductor is usually subjected to both transport current and magnetic field, so that there is a trade-off between the two effects.In this paper we investigate, both experimentally and by means of finite-element method calculations, the ac loss behavior of a stack composed by a finite number of tapes in different working conditions, and we compare the AC losses to the ones of non-interacting tapes in order to determine if the use of stacked tapes is advantageous from the point of view of power dissipation.

Observations from the Analyses of Magnetic Field and AC Loss Distributions in the NHMFL 32 T All-Superconducting Magnet HTS Insert

2013 ◽  
Vol 23 (3) ◽  
pp. 4300704-4300704 ◽  
Author(s):  
Andrew Gavrilin ◽  
Jun Lu ◽  
Hongyu Bai ◽  
David Hilton ◽  
W Markiewicz ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Superconducting Magnet ◽  
Coated Conductors ◽  
Ac Loss ◽  
Ac Losses ◽  
Magnet System ◽  
Field Gradients ◽  
The Magnetic Field ◽  
Helium Vapor

A 17 T high-temperature superconducting two-coil magnet (insert) to be operated in a 15 T low-temperature superconducting multisection magnet (outsert) is the most demanding part of the National High Magnetic Field Laboratory all-superconducting 32 T magnet system. The HTS coils are of the pancake type and to be wound with REBCO coated conductors/tapes manufactured by SuperPower, Inc. The distribution of AC losses in the HTS windings during the magnet charging/discharging process are computed and analyzed with due regard for the AC loss density dependence on the magnetic field and the field angle. The calculations are based on the measured magnetization of a representative sample against magnetic field and field angle. The results enable determination of heat load on the magnet and its cryogenic system. Since the magnet is of the pool-cooled type, a related helium vapor bubble problem can develop owing to the high field and field gradients, and the diamagnetic susceptibility of helium.

AC Losses of YBCO Coated Conductor with Ferromagnetic Substrate in DC Field

2013 ◽  
Vol 745-746 ◽  
pp. 191-196
Author(s):  
Guo Min Zhang ◽  
Zhen Ling Xu ◽  
Hui Yu ◽  
Jin Cheng Li
Keyword(s):  
Magnetic Fields ◽  
Nickel Alloy ◽  
Loss Factor ◽  
Coated Conductors ◽  
Ac Loss ◽  
Ac Losses ◽  
Coated Conductor ◽  
Background Magnetic Field ◽  
Repressive Effect ◽  
Transport Loss

As YBCO coated conductors are usually prepared on nickel or nickel alloy substrates, additional ferromagnetic losses are generated in the substrates when the conductors are exposed to AC magnetic fields or carrying alternative currents in practical application. In this work, AC transport loss factors of YBCO tapes with Ni-W alloy substrates were studied in DC magnetic fields. The influence of ferromagnetic substrate on AC loss and the repressive effect of DC background magnetic field on ferromagnetic loss in the substrate were presented and analyzed. The results showed that the AC transport loss factor of YBCO tape with Ni-W substrate decreased gradually with the increasing background field, and the minimum value of AC loss factor appeared as the field reach to about 18 mT and 45 mT for parallel and perpendicular applied field respectively. Based on the analysis, the method to reduce AC transport current loss in coated conductor with nickel alloy substrate is proposed.

scholarly journals Effect of Substrate Layer Thickness on the AC Losses in Stacked Superconducting Pancake Coils using Direct H-formulations

2019 ◽  
Vol 9 (1S3) ◽  
pp. 150-154
Keyword(s):  
High Speed ◽  
Volume Fraction ◽  
Substrate Material ◽  
Coated Conductors ◽  
Ac Loss ◽  
Ac Losses ◽  
2Nd Generation ◽  
Electric Aircraft ◽  
Commercial Software Package ◽  
Pancake Coils

Advanced electric aircrafts are in their design phase and superconducting machines are going to be the part of such fascinating technology. In order to diminish the losses involved due to conventional copper conductors, superconductors are proposed for the electric aircraft applications by the American research agencies like NASA and AFRL. Usually, Pancake coils are frequently used in various electric aircraft power applications including high speed motors, generators, transformers and solenoid magnets. Coils are generally bound with high temperature superconducting (HTS) tapes like BSCCO and YBCO. Mostly, 2nd generation coated conductors (YBCO) are employed in power applications due to their merits over BSCCO (1st generation tapes). A superconducting tape manufactured by SuperPower through iBAD manufacturing technique generally consist copper stabilizer, silver over-layer, YBCO layer, buffer layer, substrate material followed by copper stabilizer. The volume fraction of the substrate material and copper stabilizer is more than 90% in the proposed tape. In the present work, the thickness of the substrate material has been varied to evaluate the AC losses involved in the above mentioned applications due to time-varying magnetic fields. A current of 270 A (Ic=330 A) is flowing through a coil of 108 turns. AC loss has been evaluated for various thicknesses 30 µm to 90 µm at a frequency of 50 Hz. The simulations are done using COMSOL MultiPhysics® commercial software package.

scholarly journals Alternating Current Loss of Superconductors Applied to Superconducting Electrical Machines

Energies ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 2234
Author(s):  
Hongye Zhang ◽  
Zezhao Wen ◽  
Francesco Grilli ◽  
Konstantinos Gyftakis ◽  
Markus Mueller
Keyword(s):  
Quantitative Analysis ◽  
Power Density ◽  
High Efficiency ◽  
Alternating Current ◽  
Coated Conductors ◽  
Ac Loss ◽  
Electrical Machines ◽  
Qualitative And Quantitative Analysis ◽  
Qualitative And Quantitative ◽  
Reduction Techniques

Superconductor technology has recently attracted increasing attention in power-generation- and electrical-propulsion-related domains, as it provides a solution to the limited power density seen by the core component, electrical machines. Superconducting machines, characterized by both high power density and high efficiency, can effectively reduce the size and mass compared to conventional machine designs. This opens the way to large-scale purely electrical applications, e.g., all-electrical aircrafts. The alternating current (AC) loss of superconductors caused by time-varying transport currents or magnetic fields (or both) has impaired the efficiency and reliability of superconducting machines, bringing severe challenges to the cryogenic systems, too. Although much research has been conducted in terms of the qualitative and quantitative analysis of AC loss and its reduction methods, AC loss remains a crucial problem for the design of highly efficient superconducting machines, especially for those operating at high speeds for future aviation. Given that a critical review on the research advancement regarding the AC loss of superconductors has not been reported during the last dozen years, especially combined with electrical machines, this paper aims to clarify its research status and provide a useful reference for researchers working on superconducting machines. The adopted superconducting materials, analytical formulae, modelling methods, measurement approaches, as well as reduction techniques for AC loss of low-temperature superconductors (LTSs) and high-temperature superconductors (HTSs) in both low- and high-frequency fields have been systematically analyzed and summarized. Based on the authors’ previous research on the AC loss characteristics of HTS coated conductors (CCs), stacks, and coils at high frequencies, the challenges for the existing AC loss quantification methods have been elucidated, and multiple suggestions with respect to the AC loss reduction in superconducting machines have been put forward. This article systematically reviews the qualitative and quantitative analysis methods of AC loss as well as its reduction techniques in superconductors applied to electrical machines for the first time. It is believed to help deepen the understanding of AC loss and deliver a helpful guideline for the future development of superconducting machines and applied superconductivity.

scholarly journals A Feasibility Study of the Use of Smartwatches in Wearable Fall Detection Systems

Sensors ◽  
2021 ◽  
Vol 21 (6) ◽  
pp. 2254
Author(s):  
Francisco Javier González-Cañete ◽  
Eduardo Casilari
Keyword(s):  
Low Cost ◽  
Fall Detection ◽  
The Elderly ◽  
Point Of View ◽  
False Alarms ◽  
Battery Life ◽  
Area Network ◽  
Battery Lifetime ◽  
Detection Systems ◽  
Operational Aspects

Over the last few years, the use of smartwatches in automatic Fall Detection Systems (FDSs) has aroused great interest in the research of new wearable telemonitoring systems for the elderly. In contrast with other approaches to the problem of fall detection, smartwatch-based FDSs can benefit from the widespread acceptance, ergonomics, low cost, networking interfaces, and sensors that these devices provide. However, the scientific literature has shown that, due to the freedom of movement of the arms, the wrist is usually not the most appropriate position to unambiguously characterize the dynamics of the human body during falls, as many conventional activities of daily living that involve a vigorous motion of the hands may be easily misinterpreted as falls. As also stated by the literature, sensor-fusion and multi-point measurements are required to define a robust and reliable method for a wearable FDS. Thus, to avoid false alarms, it may be necessary to combine the analysis of the signals captured by the smartwatch with those collected by some other low-power sensor placed at a point closer to the body’s center of gravity (e.g., on the waist). Under this architecture of Body Area Network (BAN), these external sensing nodes must be wirelessly connected to the smartwatch to transmit their measurements. Nonetheless, the deployment of this networking solution, in which the smartwatch is in charge of processing the sensed data and generating the alarm in case of detecting a fall, may severely impact on the performance of the wearable. Unlike many other works (which often neglect the operational aspects of real fall detectors), this paper analyzes the actual feasibility of putting into effect a BAN intended for fall detection on present commercial smartwatches. In particular, the study is focused on evaluating the reduction of the battery life may cause in the watch that works as the core of the BAN. To this end, we thoroughly assess the energy drain in a prototype of an FDS consisting of a smartwatch and several external Bluetooth-enabled sensing units. In order to identify those scenarios in which the use of the smartwatch could be viable from a practical point of view, the testbed is studied with diverse commercial devices and under different configurations of those elements that may significantly hamper the battery lifetime.

Natural Locomotion Based on Foot-Mounted Inertial Sensors in a Wireless Virtual Reality System

2015 ◽  
Vol 24 (4) ◽  
pp. 298-321 ◽  
Author(s):  
Ernesto de la Rubia ◽  
Antonio Diaz-Estrella
Keyword(s):  
Virtual Reality ◽  
Gait Cycle ◽  
Inertial Sensors ◽  
Low Cost ◽  
Point Of View ◽  
Handheld Devices ◽  
Preliminary Evaluation ◽  
Virtual Reality System ◽  
Object Searching

Virtual reality has become a promising field in recent decades, and its potential now seems clearer than ever. With the development of handheld devices and wireless technologies, interest in virtual reality is also increasing. Therefore, there is an accompanying interest in inertial sensors, which can provide such advantages as small size and low cost. Such sensors can also operate wirelessly and be used in an increasing number of interactive applications. An example related to virtual reality is the ability to move naturally through virtual environments. This is the objective of the real-walking navigation technique, for which a number of advantages have previously been reported in terms of presence, object searching, and collision, among other concerns. In this article, we address the use of foot-mounted inertial sensors to achieve real-walking navigation in a wireless virtual reality system. First, an overall description of the problem is presented. Then, specific difficulties are identified, and a corresponding technique is proposed to overcome each: tracking of foot movements; determination of the user’s position; percentage estimation of the gait cycle, including oscillating movements of the head; stabilization of the velocity of the point of view; and synchronization of head and body yaw angles. Finally, a preliminary evaluation of the system is conducted in which data and comments from participants were collected.

Flexural Joints in Mechanisms

2000 ◽  
Author(s):  
M. P. Koster
Keyword(s):  
Consumer Goods ◽  
Design Methodology ◽  
Low Cost ◽  
Point Of View ◽  
Industrial Technology ◽  
Scientific Instruments ◽  
Manufacturing Equipment ◽  
Flexural Fatigue ◽  
Elastic Deflection ◽  
Flexural Joints

Abstract The application of flexural joints in mechanisms has a number of advantages. Extreme repeatability of position is obtained because of the absence of backlash and friction. From a tribological point of view, no lubrication is needed and no wear exists. In many cases their application gives rise to a low cost assembly. Flexural elements have their particular drawbacks as well. Deflections are limited; only oscillating motions can be performed and work has to be done as a consequence of the elastic deflection. Flexural fatigue sets another limit to their application. The paper gives an overview of a design methodology that has been developed at the Philips Center for Industrial Technology by the author and his colleagues over the last several decades. Some aspects of this methodology are well known; other aspects are unique. The methodology is described in detail in a book by the author about design principles (Koster 1998). The methodology has been used to design hundreds of practical mechanisms incorporated in scientific instruments, manufacturing equipment and consumer goods. Many examples are given in (Koster 1998). Several interesting examples are given in this paper.

Contact resistance, coupling and hysteresis loss measurements of ITER Poloidal Field joint in parallel applied magnetic field

2021 ◽  
Author(s):  
Jianfeng Huang ◽  
Y. Ilyin ◽  
W.A.J. Wessel ◽  
Ruben Lubkemann ◽  
Erik Krooshoop ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Contact Resistance ◽  
Applied Magnetic Field ◽  
Applied Field ◽  
Simulated Data ◽  
Hysteresis Loss ◽  
Ac Loss ◽  
Field Conditions ◽  
Ac Losses ◽  
First Time

Abstract The inter-strand contact resistance and AC losses were measured on an ITER PF Coil joint in a parallel applied AC magnetic field. In addition, the hysteresis loss was measured as a function of the angle with the applied magnetic field on a NbTi strand of the same type as in the joint with a Vibrating Sample Magnetometer (VSM). The AC loss measurements were performed at four applied field conditions for combinations of 0 or 1 T offset field and 0.2 or 0.4 T sinusoidal amplitude. The hysteresis loss of the joint was compared with the measured AC loss density of the NbTi strand for the same field conditions as the joint AC loss measurement but with varying the angle of the applied field. The subsequent cable twist angles affect the hysteresis loss since the critical current and penetration field depend on the angle of the applied field. It is found that 15.5° is an effective angle for the calculation of the hysteresis loss of joint when compared to the single strand measurement. The inter-strand contact resistance measurements cover all the typical strand combinations from the five cabling stages of the individual conductors, as well as the strand combinations across the two conductors to characterize the inter-strand including the copper sole resistivity. It’s the first time to measure the contact resistances and AC losses of the full-size ITER PF joint. By comparing the measured and simulated data in the JackPot-ACDC model, it’s also the first time to obtain the accurate inter-strand, inter-petal and strand to copper sole contact resistivities, which are the main input parameters for the further quantitative numerical analysis of the PF joints, in any current and magnetic field conditions.

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