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An overview of the research and developments into new transformer
design, undertaken in the Department of Electrical and Computer Engineering,
University of Canterbury, is presented. Initially, single phase,
50 Hz, l1/0.23kV
pole mount distribution transformers were fitted with either silicon
or amorphous steel cores. The transformer tanks were filled with
either standard
transformer oil or liquid nitrogen and tested for loss performance.
Next a partial core transformer was designed, built and tested for
its
performance
in air and while immersed in liquid nitrogen. The transformer was
designed as a mock up of a proposed high temperature superconducting transformer,
but with aluminium windings. The partial core was a slug of laminated
silicon steel.
A commercial manifestation of a partial core transformer is demonstrated
in a parallel resonant compensation test method. Initially this uses
a HV inductance that supplies reactive power to the insulation of
a hydro generator stator. As a further development, the inductor
was
turned into
a resonant transformer by the addition of a LV primary. The magnetising
reactance was matched to the generator stator insulation capacitance.
A
second tunable resonant transformer was then designed. Finally, a
high temperature super-conducting transformer (HTST) has been designed
and
built. The transformer windings are configured to allow different
arrangements, namely internal primary, external primary and autotransformer.
The thrust of research in the Department of Electrical and
Computer Engineering at the University of Canterbury has been to test
the effectiveness of
using different materials in a transformer, at different temperatures
and in
different configurations. Initial research [1] illustrated the
improved mechanical properties of a selected paper insulation immersed
in
the liquid nitrogen. A simple alternative to the use of traditional
silicon
steel
in the core, is the use of amorphous steel. In addition, instead
of operating the transformer at normal temperatures and using
oil as the
insulant,
an alternative is to immerse the entire unit in liquid nitrogen
[2].
A partial core transformer was then designed [3-6], built and tested
for its performance in air and while immersed in liquid nitrogen
[7]. The transformer
was a mock up of a proposed high temperature superconducting
transformer, but with aluminium windings. The partial core was a slug
of laminated
silicon steel.
A commercial manifestation of a partial core transformer is demonstrated
in a parallel resonant compensation test method [8,9]. Initially
this used a HV inductance that supplied reactive power compensation
to a
hydro generator
unit stator. As a further development, the inductor was turned
into a resonant transformer by the addition of a LV primary.
The magnetising
reactance
was matched to the generator stator insulation capacitance. A
second tunable resonant transformer was then designed.
Finally, a high temperature super-conducting transformer (HTST)
has been designed and built. The transformer windings are configured
to allow
different arrangements, namely internal primary, external primary
and autotransformer.