Dictionary of Electrical Engineering

Commonly used terms in the Electrical industry.

ferroresonant transformer
a transformer that is designed to operate as a tuned circuit by resonating at a particular frequency.
fiber cladding
the region of an optical fiber having a lower index of refraction than the core region, to allow confinement of light in the core.
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
(1) the member of an electrical machine that provides the main magnetic flux, which then interacts with the armature causing the desired machine operation (i.e., motor or generator).

(2) a description of how a physical quantity varies as a function of position and possibly time. See also electric field, finite field.
field circuit
a set of windings that produces a magnetic field so that the electromagnetics induction can take place in electric machines.
field controlled thyristor (FCT)
a thyristor controlled by change in the magnitude of the field current.
field current control
a method of controlling the speed of a DC motor by varying the field resistance, thus producing a change in the field current.
field discharge resistor
a resistor used to dissipate the energy stored in the inductance of a field winding. It may be a standard power resistor that is connected across the winding just prior to opening the supply switch, or a permanent non-linear resistive device that has high resistance at normal voltage but low resistance when voltage rises at switching.
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.
field reversing
a method of achieving a reversal of rotation of a DC motor by reserving the field flux.
field strength
in general terms the magnitude of the electric field vector (in volts per meter) or the magnitude of the magnetic field vector (in ampere-turns per meter). As used in the field of EMC/EMI, the term is applied only to measurements made in the far field and is abbreviated as FS. For measurements made in the near field, the term
electric field strength (EFS) or magnetic field strength (MFS) is used, according to whether the resultant electric or magnetic field, respectively, is measured.
field weakening
a method of achieving speed increase in DC motors by reducing the field flux (increasing field circuit resistance).
filter
(1) a network, usually composed of inductors and capacitors (for lumped circuit), or transmission lines of varying length and characteristic impedance (for distributed circuit), that passes AC signals over a certain frequency range while blocking signals at other frequencies. A bandpass filter passes signals over a specified range (flow to fhi),
and rejects frequencies outside this range. For example, for a DBS receiver that is to receive satellite transmitted microwave signals in a frequency range of 11 GHz to 12 GHz, a band-pass filter (BPF) would allow signals in this frequency range to pass through with minimum signal loss, while blocking all other frequencies. A low-pass filter (LPF)
would allow signals to pass with minimum signal loss as long as their frequency was less than a certain "cutoff frequency" above which significant signal blocking occurs.

(2) an operator that transforms image intensity Ix of pixel x into a different intensity îx, depending on the values of a set of (usually neighboring) pixels (which may or may not include x). Filtering is performed to enhance significant features of an image or to remove nonsignificant ones or noise. filter bank a set of filters consisting of a bank of analysis filters and a bank of synthesis filters. The analysis filters decompose input signal spectra into a number of directly adjacent frequency bands for further processing, and the synthesis filters recombine the signal spectra from different frequency bands.
filtering
(1) an estimation procedure in which the present value of the state vector (see the definition) is estimated based on the data available up to the present time.

(2) the process of eliminating object, signal or image components which do not match up to some pre-specified criterion, as in the case of removing specific types of noise from signals. More generally, the application of an
operator (typically a linear convolution) to a signal.
fin efficiency
a thermal characteristic of an extended surface that relates the heat transfer ability of the additional area to that of the base area.
finger stick
an insulated stick like a hot-stick used to actuate a disconnect-switch atop a pole.
firm power
an amount of electric power intended to be available at all times to a commercial customer, regardless of system conditions.
fission
the nuclear reaction in which a single heavy nucleus is split into two or more lighter nucleii called "daughter" products and emit highly energetic sub-atomic particles plus energy in the process.
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