Transport AC Loss Measurements of a Triangular Epoxy-Impregnated High-Temperature Superconducting Coil (original) (raw)
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IEEE Transactions on Applied Superconductivity, 2011
AC loss can be a significant problem for any applications that utilize or produce an AC current or magnetic field, such as an electric machine. The authors are currently investigating the electromagnetic properties of high temperature superconductors with a particular focus on the AC loss in coils made from YBCO superconductors. In this paper, a 2D finite element model based on the H formulation is introduced. The model is then used to calculate the transport AC loss using both a bulk approximation and modeling the individual turns in a racetrack-shaped coil. The coil model is based on the superconducting stator coils used in the University of Cambridge EPEC Superconductivity Group's superconducting permanent magnet synchronous motor design. The transport AC loss of a stator coil is measured using an electrical method based on inductive compensation using a variable mutual inductance. The simulated results are compared with the experimental results, verifying the validity of the model, and ways to improve the accuracy of the model are discussed.
Measurement of AC Losses in a Racetrack Superconducting Coil Made from YBCO Coated Conductor
Physics Procedia, 2012
We present the results of transport measurements of AC losses in a racetrack shaped superconducting coil made from coated conductor tape. The outer dimensions of the coil are approximately 24 cm × 12 cm and it has 57 turns. The coil is impregnated with epoxy resin and fiberglass tape is used to insulate the individual turns and to improve the mechanical properties of the epoxy when exposed to thermal cycling. The coil is manufactured as a part of the field winding of a small synchronous generator; therefore stainless steel frames are installed on the inner and outer side of the winding to reinforce it. The AC loss is measured versus the transport current I a with the coil immersed in liquid nitrogen. Measurements at frequencies 21 Hz, 36 Hz and 72 Hz are compared. The AC losses follow I 2 a dependence at low current amplitudes and I 3 a at high amplitudes. After cutting the inner steel frame the low amplitude losses are decreased, their frequency dependence is reduced but their dependence on the current remains unchanged.
AC loss in a high-temperature superconducting coil
Physica C: Superconductivity, 1998
In a typical superconducting coil made of BSCCOrAg tape, both amplitude and direction of the magnetic field determine the critical current, resistive voltage and AC loss. The distribution of the magnetic field along and across the superconducting tape in a coil is rather complex. This gives rise to the question: how accurate can one predict the critical current, V-I characteristic and AC loss of the AC coil from results of short sample measurements? To answer this question, we have measured and compared the characteristics of a short sample and a small coil employing ; 14 m of the same tape at 77 K. The comparison is performed as follows. First, a short sample is characterised with regard to the field dependence of the critical current, V-I characteristic and the AC loss. Second, the distribution of the magnetic field along the tape in a coil is accurately calculated. From the data, the voltage along the tape and the loss of the tape in the coil are found. Finally, the resistive voltage and the AC loss of the complete coil are calculated and compared to measured AC losses in the frequency range of 0 to 160 Hz, typical for power applications.
Study of AC Losses in Superconducting Electrical Components for Electrical System Design
Emerging Trends in Technological …, 2010
The purpose of the work was to study, characterize, and measure the different components of AC losses in superconductors that are part of such electrical systems as transformers, electrical motors, etc. The reason for such a study is because, if the study of losses is an important part of the design of any electrical application, in superconducting electrical systems losses determine not only their efficiency but also the capacity of the corresponding cooling system. The thesis document presented here was closed after this publication, but the study of YBCO tape is now the focus of one of our Group's research lines. Further work with this tape includes: − Study of the differences between losses in tapes with and without magnetic substrate. − Study of the influence of the magnetic substrate on nearby tapes and coil AC losses. − Study of the anisotropy of YBCO tape with and without magnetic substrate. − Study of the influence of the tape's anisotropy on the losses and practical critical current of a coil, depending on the bending curvature of the tape. The results of the work described have led to our participation in 5 international conferences in applied superconductivity, and to the publication of the articles [1-7] referenced in this summary and attached to the document.
Superconductor Science and Technology, 2009
The electromagnetic properties of a pancake coil in AC regime as a function of the number of turns is studied theoretically and experimentally. Specifically, the AC loss, the coil critical current and the voltage signal are discussed. The coils are made of Bi 2 Sr 2 Ca 2 Cu 3 O 10 /Ag (BiSCCO) tape, although the main qualitative results are also applicable to other kinds of superconducting tapes, such as coated conductors. The AC loss and the voltage signal are electrically measured using different pick up coils with the help of a transformer. One of them avoids dealing with the huge coil inductance. Besides, the critical current of the coils is experimentally determined by conventional DC measurements. Furthermore, the critical current, the AC loss and the voltage signal are simulated, showing a good agreement with the experiments. For all simulations, the field dependent critical current density inferred from DC measurements on a short tape sample is taken into account.
AC Loss Measurements of a Trapezoidal Shaped HTS Coil Using an Electrical Method
High temperature superconducting (HTS) coils of different shapes (typically circular or trapezoidal) wound on iron or ironless core are fundamental components of many superconducting electrical power devices. A 150-turn (75 turns/pancake) trapezoidal coil in double pancake configuration has been designed and realized in our laboratory of ENEA Frascati. Various epoxy resins and YBCO tapes have been tested in the temperature range room to liquid nitrogen, leading us to the choice of AmSC (American SuperconductorⓇ) tape for the winding and araldite resin for the impregnation process. The trapezoidal shape has been chosen because of its suitable geometry for practical applications, the results being complementary to what was previously achieved on round shapedHTS coils.The AC transport current losses have beenmeasured using a compensated electricalmethod and expressed in terms of a linearly frequency dependent resistance. A linear dependence of the losses resistance fromfrequency was expected and found in agreement with previous results. The current-voltage curve has been measured in zero externally applied field condition, the results being in good agreement with a numerical simulation. The magnetic field distributions, at different air gaps from coil top and zero externally applied filed condition, have been simulated and reported as well.
Applied Physics …, 2012
A two-axis goniometer for low-temperature nuclear magnetic resonance measurements on single crystals Rev. Sci. Instrum. 83, 093901 (2012) Study of second generation, high-temperature superconducting coils: Determination of critical current J. Appl. Phys. 111, 083902 Manufacturing of a superconducting magnet system for 28 GHz electron cyclotron resonance ion source at KBSI Rev. Sci. Instrum. 83, 02A347 Characteristic and magnetic field analysis of a high temperature superconductor axial-flux coreless induction maglev motor J. Appl. Phys. 111, 07E707 Design and investigations of the superconducting magnet system for the multipurpose superconducting electron cyclotron resonance ion source Rev. Sci. Instrum. 83, 02A319 Additional information on Appl. Phys. Lett.
Metrology and Measurement Systems, 2014
One of the most important parameters, crucial to applications of superconductors in cryo-electrotechnique, is power loss. Measurements of losses in superconducting long sample wires require AC magnetic fields of a special geometry and appropriate high homogeneity. In the paper part of the theoretical basis for calculations and a simple design method for a race-track coil set are presented. An example of such home-made coils, with a magnetic field uniformity of about 0.2 % over the range of about 8 cm, is given. Also a simple electronic measurement system for the determination of AC magnetization loss in samples of superconducting tapes is presented.
Experimental investigation of the loss characteristics of superconductors for AC power applications
IEEE Transactions on Magnetics, 1985
Recent studies1I2 confirm the economical feasibility of the .application of superconductors in AC power apparatus. The low-loss conductor which has been proposed still only exists in theory. Simple calculations show that the economic criterion described by Ogasawara3 and Hldsnik' is inaccurate because of an oversimplified hysteresis loss formula. A necessary modification shows that stricter demands will have to be made. As production of ultrafine filaments is abig technological problem, final diameter reduction by rolling instead of drawing is proposed. The expected better performance of a rolled composite has been verified experimentally in test coils as well as in transform&-geometry. Experimental setup and results are presented.