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AC losses in applied longitudinal magnetic fields at variable temperatures
KTH, Superseded Departments, Electrical Systems.
KTH, Superseded Departments, Electrical Systems.
2004 (English)In: IEEE transactions on applied superconductivity (Print), ISSN 1051-8223, Vol. 14, no 1, 22-27 p.Article in journal (Refereed) Published
Abstract [en]

In most power devices, the conductor is carrying anac transport current while it is exposed to an ac magnetic fieldtransverse to the current path. In certain applications, such aspower cables or a control winding in a controllable reactor, theconductors are exposed to a magnetic field component longitudinalto the tape axis that is parallel to the current path. To createan improved base for the design of such power devices it is ofinterest to study the losses in high-temperature superconductortapes due to longitudinal field in detail. We have investigated thelosses at several temperatures of a nontwisted multifilamentaryBi-2223 tape when it was exposed to a longitudinal magnetic field.The losses were measured with a calorimetric method and theresults were compared with the critical state hysteresis loss model.The hysteresis losses are dominating at power frequencies (50,60 Hz) in the investigated field range 2–200 mT and are accuratelydescribed by the critical state hysteresis model.

Place, publisher, year, edition, pages
2004. Vol. 14, no 1, 22-27 p.
Keyword [en]
AC losses, high-temperature superconductor (HTS) tape, longitudinal magnetic field.
National Category
Physical Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-6158DOI: 10.1109/TASC.2004.825389ISI: 000220946300004Scopus ID: 2-s2.0-2442688115OAI: oai:DiVA.org:kth-6158DiVA: diva2:10788
Note
QC 20100927Available from: 2006-09-22 Created: 2006-09-22 Last updated: 2011-10-31Bibliographically approved
In thesis
1. Studies of high-temperature superconducting tapes and their application in power apparatus
Open this publication in new window or tab >>Studies of high-temperature superconducting tapes and their application in power apparatus
2006 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

Intensive development in the field of high-temperature superconductors (HTS) has resulted in long length HTS with high current carrying capacity. The performance of HTS in the form of multifilamentary silver sheathed Bi-2223 tapes is close to the requirements for power application. Several power apparatus prototypes based on HTS have been and are being demonstrated. Recently the first commercial order for a HTS power apparatus was placed. Tennessee Valley Authority ordered two 12 MVA synchronous condensers with HTS rotor windings for reactive power compensation.

In most power devices the conductor is carrying an AC transport current while it is exposed to an AC magnetic field transverse to the current path. In certain applications such as multi-layer power transmission cables or the control winding in a controllable reactor, the conductors are exposed to a magnetic field component longitudinal to the tape axis that is parallel with the current path. In this thesis, the losses in HTS tapes in longitudinally applied magnetic field are investigated and a single phase small scale controllable reactor with a loss optimized HTS control winding is designed, constructed and tested.

An experimental setup to measure the losses in tapes exposed to longitudinal magnetic fields, transport currents, frequencies, and temperatures is presented. The system is based on a calorimetric loss measuring method where the losses are determined by the temperature response of the conductor when exposed to magnetic field and/or carrying transport current.

Semi-empirical loss models are developed from the results of the loss measurements of non-twisted multifilamentary Bi-2223 tapes. The losses when the sample is carrying transport currents and is exposed to longitudinal magnetic fields are found to consist of hysteresis, flux flow, and eddy current losses. The hysteresis losses can be modeled with the critical state model. The flux flow losses can be described with a power law dependent current voltage characteristic.

The loss models are well suited for the design of power devices in which HTS is exposed to longitudinal magnetic fields. Based on the knowledge of the losses a single phase small scale controllable reactor with a loss optimized HTS control winding is designed, constructed and tested. A simple model of the magnetic circuit of the controllable reactor is presented. Calculations from the model are compared with experimental measurements. The feasibility to design controllable shunt reactors with large linear dynamic range, low losses and limited harmonic distortion is demonstrated. Compared to a copper control winding the HTS control winding increases the dynamic range and reduces the size due to the high current density and reduces the losses of the control winding.

Place, publisher, year, edition, pages
Stockholm: KTH, 2006. xi, 73 p.
Series
Trita-EE, ISSN 1653-5146 ; 2006:038
Keyword
electrocity physics, magnetism, electronics engineering, electrical engineering
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-4112 (URN)91-7178-439-X (ISBN)
Public defence
2006-10-03, Fal F3, 00:00
Opponent
Supervisors
Note

QC 20100927

Available from: 2006-09-22 Created: 2006-09-22 Last updated: 2013-01-22Bibliographically approved

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