Dictionary of Electrical Engineering

Commonly used terms in the Electrical industry.

autotransformer starter
a single three-phase autotransformer or three single phase transformer used to start induction motors at a reduced voltage.
B coefficient

See loss coefficient
ballast
a starting and control mechanism for fluorescent and other types of gas-discharge lamps. Initially a ballast supplies the necessary starting (or striking) voltage in order to ionize the gas to establish an arc between the two filaments in the lamp. Once the gas is ionized, the ballast controls the input power and thus the light output to maximize the efficiency and life of the lamp.
band stop filter
filter that exhibits frequency selective characteristic such that frequency components of an input signals pass through unattenuated from input to output except for those frequency components coincident with the filter stop-band region, which are attenuated. The stop-band region of the filter is defined as a frequency interval over which frequency components of the input signal are attenuated.
band-pass network
a configuration of solely passive components or combination of active and passive components that will attenuate all signals outside of the desired range of frequency.
bandwidth
(1) the frequency range of a message or information processing system measured in hertz.
(2) width of the spectral region over which an amplifier (or absorber) has substantial gain (or loss); sometimes represented more specifically as, for example, full width at half maximum.
(3) the property of a control system or component describing the limits of sinusoidal input frequencies to which the system/component will respond. It is usually measured at the half-power points, which are the upper and lower frequencies at which the output power is reduced by one half. Bandwidth is one measure of the frequency response of a system, i.e., the manner in which it performs when sine waves are applied to the input.
(4) the lowest frequency at which the ratio of the output power to the input power of an optical fiber transmission system decreases by one half (3 dB) compared to the ratio measured at approximately zero modulation frequency of the input optical power source. Since signal distortion in an optical fiber increases with distance in an optical fiber, the bandwidth is also a function of length and is usually given as the bandwidth-distance product for the optical fiber in megahertz per kilometer.
See bandwidth-distance product
base quantity

See per-unit system
base vector
a unit vector in a coordinate direction.
basic impulse insulation level (BIL)
a measurement of the impulse withstand capability of a piece of electric power equipment based on its ability to withstand 50% of impulses applied at the BIL voltage.
basic input-output system (BIOS)
part of a low-level operating system that directly controls input and output devices.
basic lightning impulse level (BIL)
the strength of insulation in terms of the withstand voltage crest value using a standard voltage level impulse.
battery
one or more cells connected so as to produce energy.
baud rate

See baud
bearing currents
current flow in the bearings of electrical machines, because of electromagnetic unbalance in the machine
or from using high dv inverters. The latter is able to charge up the stray capacitance present between the stator and rotor and between the rotor and shaft and thus allows motor bearing currents to flow, with resulting bearing damage.
bell insulator
a type of strain insulator, shaped like saucer with ribs on its lower side and frequently used in insulator strings.
beta particle
an electron or positron emitted from a radioactive source.
bimetal overload device
an overload device that employs a bimetal strip as the actuating element. The bimetal strip consists of two metals bonded together. When heated, the bimetal strip will bend due to the different coefficients of linear expansion of the two metals. The bending operates a set of contacts that automatically removes the affected
load from the source of electrical power.
See overload relay
black start
the task of re-starting an isolated power system which is completely de-energized. Most generating plants require substantial external electric power to start. Thus a black start may be initiated by hand-starting gas turbine generators or by opening the gates of a hydroelectric generator somewhere in the system.
blackout
total loss of power to the entire power system.
blanket
an insulating rubber mat which is fitted temporarily over energized conductors to protect nearby workers.
Powered by The Filipino Engineer