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Dictionary of Electrical Engineering
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Commonly used terms in the Electrical industry.
bus differential relay
a differential relay specifically designed to protect high power buses with multiple inputs.
bus impedance matrix
See
Z-bus
bushing transformer
a potential transformer which is installed in a transformer bushing so as to take advantage of the insulating qualities of that bushing.
bypass switch
a manually-operated switch used to connect load conductors when an automatic transfer switch is disconnected.
byte
in most computers, the unit of memory addressing and the smallest quantity directly manipulated by instructions. The term "byte" is of doubtful origin, but was used in some early computers to denote any field within a word (e.g., DEC PDP-10). Since its use on the IBM "Stretch" computer (IBM 7030) and especially the IBM System/360 in the early 1960s, a byte is now generally understood to be 8 bits, although 7 bits is also a possibility.
C-element
a circuit used in an asynchronous as an interconnect circuit. The function of this circuit is to facilitate the handshaking communication protocol between two functional blocks.
cable limiter
a cable connector that contains a fuse. Cable limiters are used to protect individual conductors that are connected in parallel on one phase of a circuit.
cable tray
a specialized form of raceway used to hold insulated electric power cables in a building.
cage-rotor induction motor
an induction motor whose rotor is occupied by copper or aluminum bars, known as rotor bars, instead of windings. Also commonly referred to as a squirrel-cage induction motor.
candlepower distribution
a curve, generally polar, representing the variation of luminous intensity of a lamp or luminaire in a plane through the light center.
reactive power Q
The region of allowable operation is determined by factors such as rotor thermal limit, stator thermal limit, rated power of prime mover (alternator operation), and stability torque limit.
capacitance
the measure of the electrical size of a capacitor, in units of farads. Thus a capacitor with a large capacitance stores more electrons (coulombs of charge) at a given voltage than one with a smaller capacitance.
In a multiconductor system separated by nonconductive mediums, capacitance (C) is the proportionality constant between the charge (q) on each conductor and the voltage (V ) between each conductor. The total equilibrium system charge is zero. Capacitance is dependent on conductor geometry, conductor spatial relationships, and the material properties surrounding the conductors.
Capacitors are constructed as two metal surfaces separated by a nonconducting electrolytic material. When a voltage is applied to the capacitor the electrical charge accumulates in the metals on either side of the nonconducting material, negative charge on one side and positive on the other. If this material is a fluid then the capacitor is electrolytic; otherwise, it is nonelectrolytic.
capacitive reactance
the opposition offered to the flow of an alternating or pulsating current by capacitance measured in ohms.
capacitor bank
(1) an assembly at one location of capacitors and all necessary accessories, such as switching equipment, protective equipment, and controls, required for a complete operating installation.
(2) a group of (typically 3) capacitors mounted on an electric power line for voltage boosting or power factor correction.
capacitor-start induction motor (CSIM)
a single-phase induction motor with a capacitor in series with its auxiliary winding, producing nearly a 90. phase difference between the main winding and the auxiliary winding currents at starting. This results in a high starting torque, so this motor is used for hard-to-start loads. The auxiliary winding and capacitor are removed from the circuit by a centrifugal switch as the machine approaches operating speed.
carbon resistor thermometer
a carbon resistor whose temperature sensitivity provides good temperature resolution.
ceramic ferrite
a relatively inexpensive permanent magnet material with decent coercivity and low energy product that is composed of strontium or barium oxide and iron oxide. Also called hard ferrite.
chain reaction
a process in which high-energy neutrons emitted from fissile radioactive material are directed into more fissile material such that more neutrons are emitted. The process creates heat which is used to power thermal power plants.
charge conservation
physical law (derived from Maxwell's equations) indicating that no change in the total charge within a
certain volume can exist without the proper flow of charge (current) through that volume.
charging current
that portion of an electric power line's current which goes to charge the capacitance of the line. The charging current is not available for power transmission.