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AC losses in HTS as a function of magnetic fields with arbitrary directions
KTH, Superseded Departments, Electrical Systems.
2004 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

Although a superconductor has zero resistivity when carrying a direct current, losses do occur when it is exposed to an alternating magnetic field and/or is carrying an alternating current. The magnitude of these so-called AC losses depends on the operating temperature, the amplitude and the direction of the magnetic field, the transport current, and the frequency. Therefore, the use of high-temperature superconductors, HTSs, in electric power components such as cables, transformers or reactors, requires knowledge of the AC losses.

This thesis deals with the development of AC loss models for HTSs, mainly for Bi-2223 tapes. In particular, the orientation of the applied magnetic field is taken into account in the modelling. The basis for the models is the results of experimental investigations.

The basic concepts of HTSs with special emphasis on the modelling of AC losses are presented. These can be broken down into several components. Their sources and natures are described. One of the components is the hysteretic loss and it is the dominating loss in AC applications at power frequencies. Therefore, the other loss components are neglected in the modelling.

Models are presented and the associated parameters are investigated with respect to their dependence of the magnetic field as well as the temperature. The AC losses for parallel and perpendicular magnetic field with respect to the wide side of the tape are calculated numerically. Moreover, a semi-empirical model for intermediate angels of the applied magnetic field is proposed. The comparisons show good agreement with experimental results.

Keywords: High-temperature superconductors, AC loss modelling, hysteresis, E-J characteristic.

Place, publisher, year, edition, pages
Stockholm: Elektrotekniska system , 2004.
Series
TRITA-ETS, ISSN 1650-674X ; 2004:06
Keyword [en]
Electronics, High-temperatur superconductors, AC loss modelling, hysteresis, E - J characteristic
Keyword [sv]
Elektronik
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:kth:diva-35ISBN: 91-7283-855-8 (print)OAI: oai:DiVA.org:kth-35DiVA: diva2:9311
Public defence
2004-10-22, Kollegiesalen, KTH, Valhallavägen 79, Stockholm, 10:15
Opponent
Supervisors
Note

QCR 20161026

Available from: 2004-10-10 Created: 2004-10-10 Last updated: 2016-10-26
List of papers
1. Improved experimental set-up for calorimetric AC loss measurements on HTSs carrying transport currents in applied magnetic fields at variable temperatures
Open this publication in new window or tab >>Improved experimental set-up for calorimetric AC loss measurements on HTSs carrying transport currents in applied magnetic fields at variable temperatures
2001 (English)In: Physica. C, Superconductivity, ISSN 0921-4534, E-ISSN 1873-2143, Vol. 354, no 1-4, 197-201 p.Article in journal (Refereed) Published
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-5343 (URN)10.1016/S0921-4534(01)00046-6 (DOI)
Note
QC 20111117Available from: 2004-10-10 Created: 2004-10-10 Last updated: 2017-11-30Bibliographically approved
2. AC losses in a BSCCO/Ag tape carrying AC transport currents in AC magnetic fields applied in different orientations
Open this publication in new window or tab >>AC losses in a BSCCO/Ag tape carrying AC transport currents in AC magnetic fields applied in different orientations
2001 (English)In: IEEE transactions on applied superconductivity (Print), ISSN 1051-8223, E-ISSN 1558-2515, Vol. 11, no 4, 4123-4127 p.Article in journal (Refereed) Published
Abstract [en]

In most prospective electric power applications of high-temperature superconductors (HTSs), the conductor is wound in a coil configuration. For a coil of finite length, the magnetic field orientation is axial in the middle of the coil, while the field contains a substantial radial component at the coil ends. In a superconducting BSCCO/Ag tape, the ac losses depend strongly on the orientation of the magnetic field. In this study, we present experimental results of the ac losses in a multifilamentary silver-sheathed Bi-2223 HTSs tape, carrying alternating transport currents in externally applied alternating magnetic fields at different orientations, with respect to the face of the tape and perpendicular to the transport current. The ac losses were measured calorimetrically, at fixed temperature and frequency. The results are compared to semi-empirical models of the ac losses in HTSs tape. We present a more general model of the angular dependence of the ac losses.

Keyword
AC losses, calorimetric measurement, HTS, magnetic field orientations, transport current
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-5344 (URN)10.1109/77.979853 (DOI)000173370100003 ()
Available from: 2004-10-10 Created: 2004-10-10 Last updated: 2017-11-30Bibliographically approved
3. AC losses in high-temperature superconducting tapes exposed to longitudinal magnetic fields
Open this publication in new window or tab >>AC losses in high-temperature superconducting tapes exposed to longitudinal magnetic fields
2001 (English)In: Cryogenics (Guildford), ISSN 0011-2275, E-ISSN 1879-2235, Vol. 41, no 10, 721-724 p.Article in journal (Refereed) Published
Abstract [en]

The AC losses in a high-temperature superconducting (HTS) tape were measured calorimetrically in longitudinal magnetic fields while carrying transport currents. The experimental data were compared to relevant loss equations based on the critical state model. Also, with no transport current, the longitudinal losses were compared to losses due to perpendicular and parallel magnetic fields. At high magnetic fields the AC losses in longitudinal fields were one-third of those in parallel field. These relatively low losses make the HTS tapes available today competitive to conventional conductors in special applications where the conductor is exposed to longitudinal magnetic fields.

Keyword
AC losses, HTS tape, Longitudinal magnetic field
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-5345 (URN)10.1016/S0011-2275(01)00137-0 (DOI)000173836500004 ()
Available from: 2004-10-10 Created: 2004-10-10 Last updated: 2017-11-30Bibliographically approved
4. AC losses in high-temperature superconducting tapes exposed to perpendicular magnetic fields combined with transport currents
Open this publication in new window or tab >>AC losses in high-temperature superconducting tapes exposed to perpendicular magnetic fields combined with transport currents
2002 (English)In: Superconductors Science and Technology, ISSN 0953-2048, E-ISSN 1361-6668, Vol. 15, no 4, 572-576 p.Article in journal (Refereed) Published
Abstract [en]

AC losses are of great importance when designing devices for electric power applications based on high-temperature superconducting (HTS) tapes. In order to obtain an optimized design one needs to be able to calculate the AC losses that appear in an actual application. One important quantity is the AC losses that appear at the ends of a coil where the magnetic field contains a component perpendicular to the face of the tape. In this study we calculate the AC losses due to the combined action of a perpendicular magnetic field and a transport current. The results are compared to calorimetrically measured data of the AC losses in a BSCCO/Ag HTS tape.

National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-5346 (URN)10.1088/0953-2048/15/4/315 (DOI)000175333300016 ()
Available from: 2004-10-10 Created: 2004-10-10 Last updated: 2017-11-30Bibliographically approved
5. Temperature dependence of AC losses in a BSCCO/Ag tape exposed to AC magnetic fields applied in different orientations
Open this publication in new window or tab >>Temperature dependence of AC losses in a BSCCO/Ag tape exposed to AC magnetic fields applied in different orientations
2002 (English)In: Physica. C, Superconductivity, ISSN 0921-4534, E-ISSN 1873-2143, Vol. 372, 1818-1822 p.Article in journal (Refereed) Published
Abstract [en]

When high-temperature superconducting tapes are used in electrotechnical applications, they have an optimal working point in temperature. In the winding of e.g. a transformer the conductor carrying an AC current is exposed to an AC magnetic field oriented differently in separate parts of the winding. To determine the optimal working temperature it is essential to study the temperature dependence of the AC losses under these conditions. In this study, we present experimental results of the losses in a multi-filamentary silver-sheathed Bi-2223 high-temperature superconducting tape carrying an AC transport current in an AC magnetic field applied in different orientations perpendicular to the current path. The losses were measured calorimetrically in the temperature interval 40-85 K. The experimental results are compared to semi-empirical models of the AC losses.

Keyword
high-temperature superconductor, AC losses, field orientations, temperature dependence
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-5347 (URN)10.1016/S0921-4534(02)01134-6 (DOI)000178019100123 ()
Note
5th European Conference on Applied Superconductivity (EUCAS 2001) Location: TECH UNIV DENMARK, LYNGBY, DENMARK Date: AUG 26-30, 2001 Available from: 2004-10-10 Created: 2004-10-10 Last updated: 2017-11-30Bibliographically approved
6. Calculation of AC losses in HTS with power law current-voltage characteristics
Open this publication in new window or tab >>Calculation of AC losses in HTS with power law current-voltage characteristics
2003 (English)In: Proceedings of the Conference EUCASArticle in journal (Refereed) Accepted
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-5348 (URN)
Note
QC 20111110Available from: 2004-10-10 Created: 2004-10-10 Last updated: 2011-11-10Bibliographically approved

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