T
T
common symbol for temperature, usu-
ally expressed in degrees Kelvin.
T-bracket
a metal frame which holds a
lightning arrester and a cut-out to the top of
a utility pole.
T-connection
term often used to describe,
with some ambiguity, two distinct trans-
former connections — one to simply convert
voltage levels in a 3-phase power system, and
the other to convert between 3-phase and a
2-phase voltages. Both connections use only
two single-phase transformers, one called the
main and the other the teaser, arranged in a T
configuration. Details of each configuration
are described below. These connections are
also often referred to as Scott connections,
since they were first proposed by Charles F.
Scott.
Conversion of 3-phase voltage levels: In
this configuration, the main transformer in
the T-connection is a center-tapped unit that
is connected between two lines of the three-
phase system. The teaser transformer is con-
nected between the center-tap of the main
transformer and the third line of the 3-phase
power system. Additionally, the coils of the
teaser transformer have 86.6% of the turns
in the corresponding coils in the main trans-
former. The result is a balanced three-phase
voltage on the secondary. In most applica-
tions, the main and teaser transformers are
actually identical, full voltage units with cen-
ter taps and two 86.6% taps, one with respect
to each terminal. This allows main and teaser
units to be interchanged, plus it provides for
true, 3-phase, 4-wire system with a neutral
connection. This is illustrated in the diagram.
Conversion of 3-phase to 2-phase voltage:
The main and teaser transformers in this con-
nection are arranged as they are in the Scott
connection. However, while the voltage con-
nections to the primary of the teaser coil are
made at the 86.6% tap, the secondary volt-
age is taken from the full coil. This produces
two equal secondary voltages with a 90 de-
gree phase difference, as illustrated in the di-
agram. See also
teaser transformer
.
Scott transformer connection.
T transformer connection.
t-conorm
See
triangular co-norm
.
t-norm
See
triangular norm
.
c
2000 by CRC Press LLC