Page 31 - Electrical Engineering Dictionary

AC/AC converter a power electronics ation error to a constraint on the gain of the
device in which an AC input voltage of some open loop system. The relevant equations
2
magnitude, frequency, and number of phases are e a = 1 and K a = lim s→inf ty s q(s),
K a
is changed to an AC output with changes to where q(s) is the transfer function model
any of the previously mentioned parameters. of the open loop system, including the con-
AC/AC converters usually rectify the input troller and the process in cascade, and s is
source to a DC voltage and then invert the the Laplace variable. See also position error
DC voltage to the desired AC voltage. constant, velocity error constant.

AC/DC converter See rectifier. accelerator (1) a positive electrode in a
vacuum tube to accelerate emitted electrons
AC-DC integrated system a power sys- from its cathode by coulomb force in a de-
tem containing both AC and DC transmission sired direction.
lines.
(2) a machine used to impart large kinetic
energies to charged particles such as elec-
ACARS aircraft communications ad-
trons, protons, and atomic nuclei. The ac-
dressing and reporting. A digital commu-
celerated particles are used to probe nuclear
nications link using the VHF spectrum for
or subnuclear phenomena in industrial and
two-way transmission of data between an air-
medical applications.
craft and ground. It is used primarily in civil
aviation applications.
acceptable delay the voice signal de-
lay that results in inconvenience in the voice
ACC See automatic chroma control.
communication. A typically quoted value is
300 ms.
accelerated testing tests conducted at
higher stress levels than normal operation but
acceptance in an accelerator, it defines
in a shorter period of time for the specific
how "large" a beam will fit without scrap-
purpose to induce failure faster.
ing into the limiting aperture of a transport
line. The acceptance is the phase-space vol-
accelerating power the excess electric
ume within which the beam must lie to be
power at a synchronous machine unit which
transmitted through an optical system with-
cannot be transmitted to the load because of
out losses. From an experimenters point
a short circuit near its terminals. This energy
of view acceptance is the phase-space vol-
gives rise to increasing rotor angle.
ume intercepted by an experimenter’s detec-
tor system.
acceleration error the final steady dif-
ference between a parabolic setpoint and the
process output in a unity feedback control acceptor (1) an impurity in a semicon-
system. Thus it is the asymptotic error in po- ductor that donates a free hole to the valence
band.
sition that arises in a closed loop system that
is commanded to move with constant acceler- (2) a dopant species that traps electrons,
ation. See also position error, velocity error. especially with regard to semiconductors.
acceleration error constant a gain K a access channel a channel in a communi-
from which acceleration error e a is read- cations network that is typically allocated for
ily determined. The acceleration error con- the purpose of setting up calls or communi-
stant is a concept that is useful in the design cation sessions. Typically the users share the
of unity feedback control systems, since it access channel using some multiple access
transforms a constraint on the final acceler- algorithm such as ALOHA or CSMA.

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2000 by CRC Press LLC