AC source - a voltage/cuffent that periodically changes
polarity and is used as the input prime power for a power system. The AC
source is typically provided to the weapon system by central platform
alternator. An AC source may also be the output of an inverter,
frequency changer or uninteruptable power supply.
Ambient temperature - the local temperature existing prior
to any influence or change brought about by a dissipative device or
Ampacity - the current handling capacity of a conductor
expressed in amperes.
Amplifier - a circuit, component or apparatus that
provides gain (as to amplify).
Apparent power - the value obtained by the product of rms
voltage times the rms current in an AC circuit but which is not necessarily
equal to the work (power) because of phase displacement.
Arc - an electrical discharge or series of discharges
between two electrodes.
Auto-transformer - a transformer having a single
winding without primary to secondary isolation.
Backfeeding - a situation whereby a regenerative load may
cause energy or current to flow back into the output of a power conditioner
and is usually undesirable.
Balun - meaning balanced/unbalanced (as in a choke or
transformer) for matching or separating coupling impedances (common-mode vs
Bandwidth - the breadth of a set or band of frequencies
bounded by an upper and lower limit.
Bead - a small magnetic core used as a high frequency
attenuator that dissipates unwanted energy as heat.
Bleeder resistor - a resistor used to discharge a
capacitor or to constitute a minimal load on a power supply.
Brownout - a voltage just below normal deviations that may
cause degraded mode performance and which may also be harmful to electrical
Built-In-Test-Equipment (BITE) - internal circuitry that
constitutes integrated or onboard diagnostic function(s) to facilitate
real-time status reporting of the power supply's performance/temperature and
Bulk power conversion - a central point of power
conditioning with the output voltage forming an intermediate bus, which may be
either AC or DC.
Bus - usually a robust common conductor of power to
distribute high currents with minimal losses and having low impedance to
Capacitive reactance (Xc) - an opposition to the changing
of a voltage across a capacitor through current movement into/out-of the
Center-tap - a connection to an intermediate winding of a
transformer or inductor for voltage granularity.
Choke - an inductor used to impede currents of different
frequencies as in filters and attenuators.
Closed loop gain - the ratio of magnitude (usually in
voltage) between the output of an amplifier and its input, sometimes expressed
as Av or in dB.
Cold plate - the surface on which a component or assembly
is placed to transfer heat.
Common mode output current - the equal and coincident
current that flows on both output leads of a power supply and is returned to
its source via the chassis or frame of the unit.
Comparator - an amplifier used to compare one voltage to
another for purposes of deciding an action (i.e., whether to go into
over-voltage or over-cuffent or to issue a power-on-reset to logic).
Complementary tracking - an interconnection between two
voltages or supplies which causes them to maintain a proportional but opposing
relationship in the magnitude of their outputs from zero through their final
Constant current supply - a power supply that acts to
maintain a specific output current into any load resistance or voltage through
an internal gain compensated control servo.
Copper loss - the amount of power lost as heat in
transformer windings or other conductors in motors/generators, which is
sometimes stated as 12 R losses.
Corona - a luminous discharge of electricity due to the
ionization of air which appears on the surface of a conductor when the
potential gradient exceeds the ionic breakdown voltage.
Creepage distance - the separation between two conductors
which, at a given density and pressure, may cause current to begin to flow at
a specific voltage which may form an arc plasma.
Crest factor - the relationship between the peak voltage
or current and the rms value as a ratio used in determining the utilization
power factor of an AC energy source.
Cross coupling - an intentional linkage between
independent elements to coordinate regulation or proportional tracking or
sequencing of two or more outputs.
Cross regulation - the inteffelational reaction of the
load changing on one output of a multiple output power supply and its
influence upon the voltage of a companion's output.
Crowbar - a transistor or thyristor used to pull-down and
clamp the output of a power supply to approximately zero volts to avoid damage
to load components/equipments in the event of the output rising beyond their
safe operating limit.
Current limiting - a technique of various configurations,
which provide protection from damage to the power supply from load shorts or
excessively large loads (e.g., foldback, constant power)
Current sharing - a technique by which multiple power
supplies are connected in parallel or in a redundancy scheme which promotes
proportional sharing of the load across all current providing elements of the
power system. The employment can be through passive adjustment or by
cross-coupling active circuits integral to each control