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 same as for a delta-delta bank. Open-delta banks have two important roles in power distribution.
First, they allow operation at reduced initial investment on systems subject to future expansion.
A balanced three-phase load can be served with an open-delta bank, allowing future expansions
in load up to 72 percent of the open-delta rating, simply by adding the third transformer.
Second, a distribution system, that is reasonably well balanced, can be operated at reduced load
while one transformer is being serviced or replaced. This is particularly important in plants that
can reduce throughput at low cost but cannot afford periods of shutdown for significant portions
of the load being served.
3.2.7.7 Scott Connection. The Scott connection is a means of converting three-phase to
two-phase transformations or vice versa. Usually, two identical transformers are purchased so
that they will be interchangeable. This requires an 0.866 tap on one transformer and a
midwinding tap on the other. The Scott connection is shown in Figure 3-7.
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