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 TM 5-685/NAVFAC MO-912
CURRENT IN AMPERES AT-
a
07
06
01
CURRENT IN AMPERES AT 13.8K VOLTS
Figure 5-3. Typical time-current characteristic curve.
either a toroid (doughnut) winding with a primary
(CT) is an instrument transformer having low
conductor wire passing through the "hole", or a sec-
losses whose purpose is to provide a f'ixed primary
tion of bus bar (primary) around which is wound the
to secondary step down current ratio. The primary
secondary. The bus bar CT is inserted into the bus
to secondary current ratio is in inverse proportion to
being measured. The CT ratio is selected to result in
the primary to secondary turns ratio. The secondary
a five ampere secondary current when primary
winding thus has multiple turns. The CT is usually
rated current is flowing (see fig 5-4).
5-4
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