Buck and boost transformers for single-phase applications
have a dual-voltage primary rated at 120/240 V.
A choice of two sets of secondary voltages is available,
depending upon the amount of boosting or bucking required:
12/24 V and 16/32 V. Three-phase applications
from 380 V to 500 V requires the use of a buck and
boost transformer with a 240/480-V primary and a 24/
48-V secondary. A typical buck and boost transformer is
shown in Figure 14-22.
A buck and boost transformer, when used as an auto transformer
for bucking or boosting, can supply a load
which requires several times the k VA rating of the transformer.
The maximum k VA rating of the load supplied
depends upon the full-load current rating of the transformer
secondary and the operating voltage of the load.
Each manufacturer supplies load current and k VA data
for buck and boost transformers for all combinations of
input and output voltages.
The manufacturer also supplies complete wiring diagrams
for both single- and 3-phase applications.