High Temperature Superconducting (HTS)Partial Core Transformers
Andrew Lapthorn
A thesis presented for the degree of
Doctor of Philosophy in
Electrical and Computer Engineering
at the
University of Canterbury,
Christchurch, New Zealand
ABSTRACT
The thesis begins by providing an introduction to transformer theory. An ideal transformer is
examined first, followed by full core transformer theory. The partial core transformer is then
introduced and compared to the full core design. An introduction to superconductors is then
presented where a simplified theory of superconductivity is given. High temperature superconductors are then examined including their physical structure, superconducting properties and
the design of the superconducting wire.
The early development of high temperature superconducting partial core transformers at the
University of Canterbury is then examined. Early partial core development is discussed followed
by some material testing at cryogenic temperatures. This work lead into the development of the
first high temperature superconducting partial core transformer. This transformer failed during
testing and an examination of the failure mechanisms is presented. The results of the failure
investigation prompted an alternative winding insulation design which was implemented in a
full core superconducting transformer.
The modelling used to design a high temperature superconducting partial core transformer is
then presented. Based upon the reverse design method, the modelling is used to determine the
components of the Steinmetz equivalent transformer circuit. The modelling includes a combination of circuit theory and finite element analysis. An ac loss model for high temperature
superconductors is also presented.
A new 15 kVA, 230-230 V high temperature superconducting partial core transformer was designed, built and tested. The windings are layer wound with first generation Bi2223 high temperature superconductor. The modelling was used to predict the performance of the transformer
as well as the ac losses of the high temperature superconductor. A series of electrical tests were
performed on the transformer including open circuit, short circuit, resistive load, overload, ac
withstand voltage and fault ride through tests. The test results are compared with the model.
The transformer was found to be 98.2 % efficient at rated power with 2.86 % voltage regulation.
LINK: https://core.ac.uk/download/pdf/35468185.pdf
