Doctor of Philosophy
School of Electrical, Computer and Telecommunications Engineering
Hardono, Tri, Measurement and modelling of high temperature superconductors for power engineering applications, Doctor of Philosophy thesis, School of Electrical, Computer and Telecommunications Engineering, University of Wollongong, 2001. http://ro.uow.edu.au/theses/1955
High temperature superconducting technology has great potential for power engineering applications. The work presented in this thesis investigates measurement and modelling techniques of high temperature superconductors (HTSCs) with the intention of contributing to the skills, tools and understanding needed to assist in utilisation of HTSCs in electrical power engineering. Investigations of short and wires, plates and coils are discussed.
Factors likely to affect the engineering performance of HTSCs in power engineering circuits are firstly discussed. An extensive test-rig has been assembled comprising cryogenic parts, instrumentation and a computerised data collecting system. Detailed measurements are made on the effects of magnetic fields and mechanical strains on HTSC performance.
A new method for AC loss measurement of short HTSC wire using a calorimeter has been investigated and demonstrated. Calorimeters have been used before and have the advantage of being able to measure the total losses in a wire. The calorimeter presented here has a simple construction compared with previously reported calorimeters and uses widely available Styrofoam as a thermal insulator. In addition, the calorimeter was made sufficiently small that it could be inserted into a solenoid so that measurements on the effect of an external applied field on the HTSC sample could be undertaken. This method has been used to measure losses of HTSC wires carrying AC current as well as twisted and untwisted HTSC wire exposed to an external C field. It is shown that AC losses of short HTSC wire to a level of microwatts per centimetre could be measured. Comparison between measurement results and theoretical calculations verified the accuracy of the method. Other work on AC loss measurement has also been performed on long lengths of wire and a bulk HTSC plate. The results agree approximately with the theoretical predictions.
Characterisation of and loss tests on two HTSC pancake coils carrying current have also been performed. The purpose is to investigate the behaviour of a coil as an elementary device in AC environments. The coils are prepared using Bi-2223/Ag wire. New methods in predicting the critical current of the coils have been investigated including the self-field effect in the coil and the critical current results from short lengths of the wire forming the coils. The magnetic fields generated in these coils and their effects on the coil are analysed using finite element methods verified using experimental results. AC loss prediction using face-to-face stacks of HTSC wire has also been described. A pancake coil with a relatively large diameter can be assumed as stacks of infinite wires. The prediction has been compared using the results of AC loss measurements using electrical methods.
Finally, engineering models of HTSC wire and coils have been developed. The models have two functions: to represent the behaviour of HTSC wire and coils and to predict the behaviour of prospective wire and coils. All significant factors affecting the HTSC performance have also been included in the models. Subsequently, circuit models have been developed using PSpice. These models are needed to assist in the accurate development and implementation of HTSC devices, such as coils, in power engineering systems.