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Commonly used terms in the Electrical industry.
energy gap
the width of the energy interval between the top of the valence band and the bottom of the conduction band.
energy product
the product of the magnetic flux density, Band magnetic field intensity, H at any operating point on the normal demagnetization curve, indicating the energy delivered by the magnet. The maximum energy product is commonly used to designate varying grades of materials.
entropy estimation
noiseless source coding theorem states that the bit rate can be made arbitrarily close to the entropy of the source that generated the image. Entropy estimation is the process of characterizing the source using a certain model and then finding the entropy with respect to that model. The major challenge here is to approximate the source structure as close as possible while keeping the complexity of the model and the number of parameters to a minimum.
equivalent impedance
the impedance of the windings of an electromagnetic machine reflected to one side (component) of the machine. For example, in a transformer, the equivalent impedance consists of the combined leakage reactances and resistances of the primary and secondary.
equivalent sphere illumination (ESI)
the level of sphere illumination that would produce task visibility equivalent to that produced by a specific lighting environment.
ESPRIT
acronym for estimation of signal parameters via rotational invariance techniques. A subspace-based estimation technique based on two identical, displaced sensor arrays.
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.
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.
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.
fail-stop processor
a processor that does not perform incorrect computation in the event of a fault. Self-checking logic is often used to approximate fail-stop processing.
fault prevention
any technique or process that attempts to eliminate the possibility of having a failure occur in a hardware device or software routine.
fiber-optic cable
a glass fiber cable that conducts light signals and can be used in token ring local area networks and metropolitan area networks. Fiber optics can provide higher data rates than coaxial cable. They are also immune to electrical interference.
fiber-optic interconnect
interconnect that uses an optical fiber to connect a source to a detector. An optical fiber is used for implementing a bus. The merits are large bandwidth and high speed of propagation.
field loss protection
a fault-tolerant scheme used in electric motors. Some DC motor control circuits provide field loss protection in the event the motor loses its shunt field. Under a loss of field, DC motors may overspeed causing equipment damage and/or personal injury. In a motor controller that has field loss protection, a sensor determines when the shunt field has lost current flow, then secures the motor before an overspeed condition occurs.
field propagator
the analytical description of how electromagnetic fields are related to the sources that cause them. Common field propagators in electromagnetics are the defining Maxwell equations that lead to differential equation models, Green's functions that produce integral equation models, optical propagators that lead to optics models,
and multipole expansions that lead to modal models.
firm power
an amount of electric power intended to be available at all times to a commercial customer, regardless of system conditions.
flat-compounded
characteristic of certain compound-wound DC generator designs in which the output voltage is maintained essentially constant over the entire range of load currents.