Year

1997

Degree Name

Doctor of Philosophy

Abstract

Ag-clad ceramic (Bi,Pb)2Sr2Ca2Cu3O10+x high critical temperature superconducting (HTS) wire has been developed at the University of Wollongong with respect to its critical current density, long length and mechanical flexibility. the present work, the HTS wire was investigated for making a HTS coil, an electrical fault current limiter and an electronic high voltage generator.

HTS coils were made using Ag-clad (Bi,Pb)2Sr2Ca2Cu3O10+x HTS wire prepared by the powder-in-tube technique. The HTS wire was characterised as a conductor. The anisotropic HTS wire has a strongly magnetic-field-dependent critical current, which causes critical cunent degradation when used in the form of a coil. The magnetic field behaviour of the HTS coil was studied with respect to its critical cunent and magnetic field properties. HTS solenoid and pancake coils were produced using "react and wind" and "wind and react" procedures. Experiments which were carried out included magnetic field measurements of the HTS coils in DC and AC magnetic fields, and critical current ampere-turns when used as a magnetic core bias winding. The magnetic field distribution of the HTS coils was also investigated using a magnetic field analysis computer program. The magnetic field in the radial direction (By)(//c-axis) at the HTS coil side's edge has the most influence on the HTS coil performance at 77 K. The experimental results and analysis provide basic information for the design and operation of a HTS coil made from the anisotropic Ag-clad (Bi,Pb)2Sr2Ca2Cu3O10+x wire.

The designed electrical fault crrent limiter was based on the principle of a saturable magnetic core reactor, where a DC bias winding with a large number of ampere-turns is required to generate a high magnetic motive force (mmf) on a magnetic core. The HTS coil was also studied for use in this device as the DC bias winding. A small laboratory device rated at 3.5 kW was made and tested to investigate the electrical behaviour of the saturable magnetic core fault cunent limiter and the HTS coil in this application. The electrical behaviour of this fault cunent limiter was also analysed using the modified device ψ-I characteristics, and also considered for application in a 6 kV power distribution system. The results show that this fault cunent limiter restricts fault cunents effectively both in the transient and steady states.

A high voltage generator device was made and analysed with regard to using a HTS wire inductor. A laboratory high voltage generator device was built, based on a R-C-L resonant circuit, where large inductance and low resistance were required to generate high voltages from a low voltage battery source. Analysis showed that by using an HTS inductor to reduce the circuit resistance, the build-up voltage could be significantly increased. 1.2 kV was generated using a small hybrid inductor from a 12 V battery source, and the potential build-up voltage when using a larger HTS inductor was shown to be very high.

Both the electrical fault cunent limiter device and the electronic high voltage generator were analysed from measurements and simulations. With improvements in critical cunents and long lengths of Ag-clad (Bi,Pb)2Sr2Ca2Cu3O10+x wires, HTS coils with high values of critical ampere-turns could be achieved at 77 K operating temperature. These will enable the above HTS applications to be practicable in electrical engineering.

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