Environmental Engineering Reference
In-Depth Information
Stator
Shaft
Cryocooler
Rotor
Figure 7: The conceptual 8 MW generator design.
necessary to design a conventional electrical machine. In addition to skills in the
fi elds of electromagnetic and mechanical engineering needed for conventional
machine design, skills are also required in the fi elds of cryogenics and vacuum
technology. There are more options open to the designer of an HTS synchronous
machine compared to a conventional machine. Since conventional electrical
machine design tools are not applicable to some of these topologies, it is necessary
to rely heavily on electromagnetic fi nite element analysis (FEA) for the design
process. The limited magnetic circuit in most HTS machine designs give no defi ned
path for the magnetic fl ux, which means that 3D electromagnetic FEA must be
used. This is an order of magnitude more time consuming than 2D analysis.
The HTS synchronous machine can be classifi ed into a number of different
types with different characteristics, advantages and disadvantages:
1.
Conventional stator with iron teeth and HTS rotor with magnetic pole bodies
which can be either warm or at cryogenic temperature. The electromagnetic
layout of this type is shown in Fig. 8 (components without an electromagnetic
function are not shown). This type does not offer much improvement in size or
mass compared to a conventional machine, but offers gains in effi ciency due to
almost zero rotor loss.
Conventional stator and HTS rotor with non-magnetic pole bodies (Fig. 9). The
2.
advantages are similar to type 1, but it requires more HTS wire to produce the
necessary stator fl ux density. It avoids potential high cost cold magnetic materials
or complex thermal isolation.
Airgap stator winding and HTS rotor with magnetic pole bodies (Fig. 10). This
3.
construction allows the fl ux density at the airgap signifi cantly beyond what is
possible with a conventional stator. The rotor iron can operate very highly satu-
rated, since the fl ux is predominantly DC. This allows signifi cant reductions in
size and mass of the HTS machine. Since most ferromagnetic materials become
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