Dictionary of Electrical Engineering

Commonly used terms in the Electrical industry.

fault prevention
any technique or process that attempts to eliminate the possibility of having a failure occur in a hardware device or software routine.
fault resistance
the resistance that occurs at the point of fault due to voltage drop across an arc or due to other resistance in the fault path.
fault secure
pertaining to a circuit, with respect to a set of faults, if and only if for any fault in this set, and any valid input code the output is a non-code or correct code (the output is never an invalid code). The circuit
is considered to operate properly if the output is a code word.
fault simulation
an empirical method used to determine how faults affect the operation of the circuit and how much testing is required to obtain the desired fault coverage.
fault tolerance
correct execution of a specified function in a circuit (system), provided by redundancy despite faults. The redundancy provides the information needed to negate the effects of faults.
fault tree
the identification and analysis of conditions and factors that cause or contribute to the occurrence of a defined undesirable event, usually one that significantly affects system performance, economy, safety, or other required characteristics.
fault-tolerant control system
a system that exhibits stability and acceptable performance in the presence of component faults (failures) or large changes in the system that resemble failures.
feedback
(1) signal or data that is sent back to a commanding unit from a control process output for use as input in subsequent operations. In a closed-loop system, it is the part of the system that brings back information on the process condition under control.

(2) the provision of a path from the output to the input of a system, such that the output may be made a function of both the input and the previous outputs of the system.

(3) the technique of sampling the output of an amplifier and using that information to modify the amplifier input signal. A portion of the output is "fed back" to the input. Positive feedback occurs when the output is added to the input; negative feedback occurs when the output is subtracted from the input. Negative feedback, invented by communications engineer Harold Black in 1928, usually results in a gain - bandwidth tradeoff: decreasing and stabilizing the amplifier gain, while increasing the bandwidth. According to Norbert Wiener, feedback is a method of controlling a system by reinserting into it the results of its past performance.
feeder
overhead lines or cables that are used to distribute the load to the customers. They interconnect the distribution substations with the loads.
feeder circuit
an electrical circuit designed to deliver power from the service equipment or separately derived system to the branch circuit panelboard(s) on a facility. For large systems, there may be more than one level of feeder circuits. See also branch circuit.
female connector
a connector presenting receptacles for the insertion of the corresponding male connector that presents pins.
ferrite
a term applied to a large group of ceramic ferromagnetic materials usually consisting of oxides of magnesium, iron, and manganese. Ferrites are characterized by permeability values in the thousands and are used for RF transformers and high Q coils.
ferrite beads
small toroids made of fer-rites which are slipped over a conductor in order to suppress RF currents. The beads act as RF chokes at high frequencies.
ferrite core
a magnetic core made up of ferrite (compressed powdered ferrromagnetic) material, having high resistivity and low eddy current loss.
ferrite core memory

See magnetic core memory
ferrite material
a material that has very low conductivity ( σ ) and very large permeability ( μ ). Its properties can be altered when an external magnetic field is applied. It is used in ferrite loaded loop antennas, for example, to increase the flux through the loop antenna.
ferroelectric material
a polar dielectric in which the crystallographic orientation of the internal dipole moment can be changed by the application of an electric field.
ferrofluid
iron based solution employed in voice coil/pole piece gap improving magnetic flux and power handling capacity.
ferromagnetic
materials in which internal magnetic moments spontaneously line up parallel to each other to form domains, resulting in permeabilities considerably higher than unity (in practice, 1.1 or more); examples include iron, nickel, and cobalt.
ferroresonance
a resonant phenomenon involving inductance that varies with saturation. It can occur in a system through the interaction of the system capacitance with the inductance of, for example, that of an open-circuited transformer. Ferroresonance resembles, to some extent, the normal resonance that occurs wherever L-C circuits are encountered. If the capacitance is appreciable, ferroresonance can be sustaining or result in a limited over voltage enough to damage the cable or the transformer itself.