Electrical Engineers and Master Electricians (EEAME) Portal
Home
Dictionary
Tutorials
General
Specifications
Disclaimer
Devices
Dictionary of Electrical Engineering
A
B
C
D
E
F
G
H
I
J
K
L
M
N
O
P
Q
R
S
T
U
V
W
X
Y
Z
ALL
Commonly used terms in the Electrical industry.
ESI
See
equivalent sphere illumination
ESPRIT
acronym for estimation of signal parameters via rotational invariance techniques. A subspace-based estimation technique based on two identical, displaced sensor arrays.
etching
a reactive process where material is removed from a semiconductor device or printed circuit board. Usually a photosensitive material is exposed through a photomask, and either a wet chemical process or a dry plasma process is used to selectively remove material to leave a particular pattern behind after the etch process is completed.
eutectic alloy
composition with minimum melting temperature at the intersection of twosolubility curves.
eutectic alloy overload device
an overload device that employs a melting alloy as the actuating element. See also overload heater, overload relay.
exception
(1) an unusual condition arising during program execution that causes the processor to signal an exception. This signal activates a special exception handler that is designed to handle only this special condition. Division by zero is one exception condition. Some vendors use the term "trap" to denote the same thing.
(2) an event that causes suspension of normal program execution. Types include addressing exception, data exception, operation exception, overflow exception, protection exception, underflow exception. exception handler a special block of system software code that reacts when a specific type of exception occurs. If the exception is for an error that the program can recover from, the program can recover from the error and resume executing after the exception handler has executed. If the programmer does not provide a handler for a given exception, a built-in system exception handler will
usually be called, which will result in terminating the process that caused the exception. Finally, the reaction to exception can be halting of the system. As an example, a bus error handler is the system software responsible for
handling bus error exceptions.
excess delay
the arrival times of a component of the impulse response of a wideband communication channel relative to the first arriving component. Hence the total excess delay, the difference in arrival time between the first and last significant components.
excitation system
the DC voltage source and its accompanying control and protection systems connected to the synchronous generator rotor.
exciter
a DC source that supplies the field current to produce a magnetic flux in an electric machine. Often it may be a small DC generator, placed on the same shaft of the electrical machine.
exciting current
the current drawn by a transformer primary with its secondary open circuited. It is the vector sum of the core loss current Ic and the magnetizing branch current Im . The exciting current I
e
is also the current measured in the open circuit test on a transformer. The exciting current is calculated as the ratio of the primary induced EMF and the impedance of the tank circuit. On load, it is equal to the difference between the primary and reflected secondary currents of the transformer.
explosion-proof machine
National Electrical Manufacturers Association (NEMA) classification describing an electrical machine that is totally enclosed and whose enclosure is designed to withstand an internal explosion of a specified gas or vapor that may accumulate within the enclosure. The specification also requires that the design prevent ignition of the specified gas or vapor surrounding the enclosure due to sparks, flashes, or explosions of the specified gas within the enclosure.
express feeder
a feeder to which laterals are connected only at some distance from the substation. These thus traverse areas fed by other feeders and are used to supply concentrated loads or new subdivisions. See feeder, lateral.
expulsion fuse
a fuse used on primary distribution lines which extinguishes the arc that results when it blows by explosively ejecting the fuse wire from its enclosure.
expulsion tube arrester
a gapped lightning arrester which establishes the power-follow arc in a tube lined with a substance which generates a sufficient quantity of gas when heated to blow out the arc. See power follow, lightning arrestor.
extended source
a (light) source in which rays are emitted from a large source area. Compare with point source.
externally vented machine
classification describing an electrical machine constructed with an open frame in which ventilation air is forced through the machine by blower(s) mounted outside the machine enclosure.
extinction angle
time in electrical degrees from the instant the current in a valve reaches zero (end of conduction) to the time the valve voltage changes sign and becomes positive.
extinction cross section
the sum of the scattering and the absorption cross sections.
extrinsic
associated with the outside or exterior. In devices and device modeling, extrinsic refers to that part of the device or model associated with the passive structures that provide interconnects and contacts to other components, but are still considered a part of the device.
extrinsic fiber optic sensor
a fiber optic sensor where the fiber delivers light to and from a sensing element external to the fiber. Chemical sensors are an example where the sensing element exhibits a change in optical property such as absorption, fluorescence or phosphorescence upon detection of the species to be measured.