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Figure 4-9A
Superconductors. (1) Transformers using high-temperature superconducting (HTS)
windings can operate in closed or open cycle. The cryocooled HTS transformer
operates closed cycle and all refrigeration is self-contained (middle). The open-cycle
unit (right) has an internal supply of liquid nitrogen refrigerant, which is
automatically replenished, periodically, from remotely located liquefiers or storage
vessels. Oil-filled transformers (left) in urban locations, which superconducting
transformers may replace,are often surrounded by sprinkler systems (not shown) and
oil containment structures. (Courtesy Wausheka
Electric Systems)

Figure 4-9B
This artist's conception of a
superconducting transformer
resembles conceptually the one
being developed by Intermagnetics
General and Wausheka Electric.
Note in particular the location
of the liquid-nitrogen storage vessel,
inside the top of the transformer box,
and the enclosure containing liquid
nitrogen around the primary and
secondary superconducting windings.
(Courtesy Wausheka Electric Systems)

Figure 4-9C
The 630-kVA demonstration transformer based
on high-temperature superconductor windings
is presently under test by ABB, ASEA Brown
Boveri Ltd., on the grid in Geneva, Switzerland.
Designed to convert power from 18.7 kV to 420 V,
its superconducting windings are made of
powder-in-tube BSCCO-2223. (Courtesy
Wausheka Electric Systems)

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