Delta - a three phase three wire AC energy source used
throughout electrical distribution systems and often used in shipboard
applications to minimize the amount of return current flowing in the hull.
Derating - the practice of applying components at lower than
their maximum rating (e.g., voltage, current, or temperature) to reduce stress
and provide design margins to increase reliability and operating life.
Dielectric - an insulating (non-conductive) medium
separating two or more conductors. Diode
Steering - a technique employing rectifiers or diodes to
cause current to flow in the desired circuit or direction while blocking it from
an undesired path or circuit,
Distortion - an undesirable modification of a waveshape
(usually sinusoidal) by non-linear effects/elements resulting in poor or
Droop - a decrease in voltage or current, typically of short
duration, caused by the source impedance.
Droop regulation - a form of automatic load sharing among
multiple, parallel, power supplies.
Efficiency - the
ratio of output power divided by the input power, which determines the amount
of heat, dissipated by the conversion apparatus (e.g., 80 Watts/100 Watts =
80% efficiency or 20 Watts
Electromagnetic Interference/Electromagnetic Compatibility
(EMI/EMC) - relates to the emissions made by one electrical apparatus
and the effect that those conducted or radiated energies have upon itself and
others sharing the same power source or environmental space.
EMI filter - a device usually made of passive components
which is used in conjunction with a power supply/system to attenuate the
electrical emissions generated by its operation. The EMI filter must be
designed to be compatible with its associated energy source and conversion
Encapsulation - a protective coating or potting placed
around electronic components or assemblies to stabilize and/or insulate
Excitation current - the current flowing in the winding of a
magnetic component (e.g., transformer or inductor) which establishes the
magnetic flux lines associated with local magnetization.
Faraday shield/cage - an electrostatic barrier (e.g.,
metallic screen/foil) to isolate the effects of one circuit or element on
another (e.g., between the primary and secondary windings of a transformer).
Fault response - that period of time taken for recognition
and reaction to an undesirable connection in an electrical distribution system
(e.g., shorts or unintentional grounding).
Fault tolerance - a circuit design technique used to assure
the failure of one redundant or paralleled function does not cause failure or
inhibit the proper operation of the remaining good element(s) or circuit(s).
Free wheeling diode - the rectifier used to commutate the
energy stored in the inductor of an output filter during the "OFF" time.
Frequency changer - an electronic or rotating equipment used
to convert one AC source of a given frequency to a source of a different AC
frequency (e.g., 60 Hz to 400 Hz).
Gain margin - the amplitude ratio of input signal to return
signal in a closed-loop feedback system at the frequency where the signals are
in phase and is usually expressed in dB. This is a measure of feedback
Glass transition temperature - the temperature at which a
polymer or resinous organic substance experiences a significant change in the
slope of its coefficient of thermal expansion (CTE) causing mismatches between
dissimilar materials (e.g., the shear and "Z" dimensional stress resulting at a
plated through hole (e.g., via on an epoxy glass multi-layered circuit board).
Glitch - a slang word or expression used by many to describe
a switching transient or unwanted event.
Green wire ground - a noncurrent conducting wire used to
electrically reference equipments and to provide a path for fault currents for
protection of personnel and property.
Ground - an electrical connection to which all currents
eventually flow to satisfy the laws of a complete circuit" where the algebraic
sum must equal zero.
High Density Module - a power supply module, which is
usually encapsulated in plastic or epoxy and is a relatively inexpensive
building block from which a power system can be assembled. Sometimes an
EMI filter and an intermediate voltage (line conditioner) are necessary to
complete the power system function.
High line - the highest input voltage specified for safe
operation of a power supply or power system.
Highly Accelerated Life Testing (HALT) - a process by which
a power supply is operated and tested beyond its normal
operational/environmental limits to stimulate the failure of marginal components
Highly Accelerated Stress Screening (HASS) - a process to
identify/detect workmanship flaws, latent defects, and marginal designs.
High Voltage Power Supply - a supply whose output is in
excess of 300 volts,
Hold-Up time - the period or length of time that electronic
equipment will continue to operate on intemally/locally stored energy when the
prime source of power is removed (usually milliseconds).
Hot swappable - a system design technique or circuit type
which facilitates the removal/replacement of modules or component elements while
the system is powered.