transform coding
a method for source
coding similar to subband coding. The in-
put signal is transformed into an alternative
representation, using an invertible transform
(e.g., the Fourier transform), and the quan-
tization is then performed in the transform
domain. The method utilizes the fact that
enhanced compression can then be obtained
by focusing (only) on “important” transform
parameters.
transform kernel
a function that is mul-
tiplied with an input function: the result of
which is integrated or summed to form a
transformed output. For example in the def-
inition of the continuous Fourier transform
the kernel is
e
−jωt
and in the definition of
the discrete Fourier transform the kernel is
e
−j2πnm/N
.
transform vector quantization
the gen-
eralization of scalar transform coding to vec-
tor coding. See also
transform coding
.
transform VQ
See
transform vector
quantization
.
transform-based heirarchical coding
use of heirarchically compacted image en-
ergies to allow recognizable reconstruction
with a relatively small amount of data.
transformation ratio
dimensionless ra-
tio of the real parts of the load and source
impedance.
transformed circuit
an original circuit
with the currents, voltages, sources, and pas-
sive elements replaced by transformed equiv-
alents.
transformer
a device that has two or more
coils wound on an iron core. Transformers
provide an efficient means of changing volt-
age and current levels, and make the bulk
power transmission system practical. The
transformer primary is the winding that ac-
cepts power, and the transformer secondary is
the winding that delivers power. The primary
to secondary voltages are related by the turns
ratio of the coils. The corresponding currents
are related inversely by the same ratio.
transformer differential relay
a differ-
ential relay specifically designed to protect
transformers. In particular, transformer dif-
ferential relays must deal with current trans-
former turns ratio error and transformer in-
rush and excitation current.
transformer fuse
a fuse employed to iso-
late a transformer from the power system in
the event of a transformer fault or heavy over-
load.
transformer vault
a fireproof enclosure
in which power transformers containing oil
must be mounted if used underground or in-
doors.
transient
(1) the behavior exhibited by a
linear system that is operating in steady state
in moving from one steady state to another.
For stable systems, the transient will decay
while for unstable system it will not, and
thus the latter never reach another steady-
state operation. See also
settling time
and
time constant
.
(2) any signal or condition that exists only
for a short time.
(3) an electrical disturbance, usually on a
power line.
(4) refers to momentary overvoltages or
voltage reductions in an electric power sys-
tem due to lightning, line switching, motor
starting, and other temporary phenomena.
transient current
the fault current that
flows during the transient period when the
machine apparent impedance is the transient
impedance.
transient fault
a fault that can appear
(e.g., caused by electrical noise) and disap-
pear within some short period of time.
transient impedance
the series impe-
dance that a generator or motor exhibits fol-
c
2000 by CRC Press LLC