PEC电气工程专业英语证书考试-基础电气工程术语和定义.doc

PEC电气工程专业英语证书考试-Basic Electrical engineering terms and definitions

Access Fitting. A fitting that permits access to conductors in concealed
or enclosed wiring, elsewhere than at an outlet.
Active Electrical Network. A network that contains one or more
sources of electrical energy.
Admittance. The reciprocal of impedance.
Air-Blast Transformer. A transformer cooled by forced circulation
of air through its core and coils.
Air Circuit Breaker. A circuit breaker in which the interruption occurs
in air.
Air Switch. A switch in which the interruption of the circuit occurs
in air.
Alive. Electrically connected to a source of emf, or electrically
charged with a potential different from that of the earth. Also,
practical synonym for current-carrying or hot.
Alternating Current. A periodic current, the average value of which
over a period is zero.
Alternator. Synchronous generator; a synchronous alternating current
machine that changes mechanical power into electrical
power.
Ambient Temperature. The temperature of a surrounding cooling
medium, such as gas or liquid, that comes into contact with the
heated parts of an apparatus.
Ammeter. An instrument for measuring electric current.
Ampere. A charge flow of one coulomb per second.
Annunciator. An electromagnetically operated signaling apparatus
that indicates whether a current is flowing or has flowed in one
or more circuits.
Apparent Power. In a single-phase, two-wire circuit, the product of
the effective current in one conductor multiplied by the effective
voltage between the two points of entry.
Appliance. Current-consuming equipment, fixed or portable, such
as heating or motor-operated equipment.
Arc-Fault Circuit Interrupter (AFCI). An electrical device that detects
the unique electronic characteristics of electrical arcs. If an
arc is sensed, the device further deenergizes the circuit to which it
is connected.
Arcing Contacts. Contacts on which an arc is drawn after the main
contacts of a switch or circuit breaker have parted.
Arcing Time of Fuse. The time elapsing from the severance of the
fuse link to the final interruption of the circuit under specified
conditions.
Arc-Over of Insulator. A discharge of power current in the form of
an arc, following a surface discharge over an insulator.
Armor Clamp. A fitting for gripping the armor of a cable at the
point where the armor terminates, or where the cable enters a
junction box or other apparatus.
Armored Cable. A cable provided with a wrapping of metal, usually
steel wires, primarily for the purpose of mechanical protection.
Arrester, Lightning. A device that reduces the voltage of a surge
applied to its terminals and restores itself to its original operating
condition.
Autotransformer. A transformer in which part of the winding is
common to both the primary and secondary circuits.
Back-Connected Switch. A switch in which the current-carrying
conductors are connected to studs in back of the mounting base.
Bank. An assemblage of fixed contacts in a rigid unit over which
wipers or brushes may move and make connection with the
contacts.
Bank, Duct. An arrangement of conduit that provides one or more
continuous ducts between two points.
Benchboard. A switchboard with a horizontal section for control
switches, indicating lamps, and instrument switches; may also
have a vertical instrument section.
Bidirectional Current. A current that has both positive and negative
values.
Bond, Cable. An electrical connection across a joint in the armor
or lead sheath of a cable, between the armor or sheath to ground,
or between the armor or sheath of adjacent cables.
Box, Conduit. A metal box adapted for connection to conduit for
installation of wiring, making connections, or mounting devices.
Box, Junction. An enclosed distribution panel for connection or
branching of one or more electric circuits without making permanent
splices.
Box, Junction (Interior Wiring). A metal box with blank cover for
joining runs of conduit, electrical metallic tubing, wireway, or
raceway and for providing space for connection and branching of
enclosed conductors.
Box, Pull. A metal box with a blank cover which is used in a run of
conduit or other raceway to facilitate pulling in the conductors; it
may also be installed at the end of one or more conduit runs for
distribution of the conductors.
Branch Circuit. That portion of a wiring system extending beyond
the final automatic overload protective device.
Branch Circuit, Appliance. A circuit supplying energy either to permanently
wired appliances or to attachment-plug receptacles such
as appliance or convenience outlets and having no permanently
connected lighting fixtures.
Branch Circuit Distribution Center. A distribution circuit at which
branch circuits are supplied.
Branch Circuit, Lighting. A circuit supplying energy to lighting outlets
only.
Branch Conductor. A conductor that branches off at an angle from
a continuous run of conductor.
Break. The break of a circuit-opening device is the minimum distance
between the stationary and movable contacts when the device
is in its open position.
Breakdown. Also termed puncture, denoting a disruptive discharge
through insulation.
Breaker, Line. A device that combines the functions of a contactor
and a circuit breaker.
Buried Cable. A cable installed under the surface of the soil in such
a manner that it cannot be removed without digging up the soil.
(Type UF is commonly used for home wiring.)
Bus. A conductor or group of conductors that serves as a common
connection for three or more circuits in a switchgear
assembly.
Bushing. Also termed insulating bushing; a lining for a hole for insulation
and/or protection from abrasion of one or more conductors
passing through it.
Cabinet. An enclosure for either surface or flush mounting, provided
with a frame, mat, or trim.
Cable. The package of wires, insulating material, sheathing, and
whatever else is necessary for the type being installed. It is usually
purchased in large spools.
Cable Fault. A partial or total local failure in the insulation or continuity
of the conductor.
Cable Joint. Also termed a splice; a connection between two
or more individual lengths of cables, with their conductors
individually connected, and with protecting sheaths over the
joint.
Cable, Service. Service conductors arranged in the form of a cable
(see Service).
Cable Sheath. The protective covering, such as lead or plastic, applied
over a cable.
Charge, Electric. An inequality of positive and negative electricity
in or on a body. The charge stored in a capacitor (condenser)
corresponds to a deficiency of free electrons on the positive
plate and to an excess of free electrons on the negative
plate.
Choke Coil. A low-resistance coil with sufficient inductance to substantially
impede ac or transient currents.
Circuit, Electric. A conducting path through which electric charges
may flow. A dc circuit is a closed path for charge flow; an ac circuit
is not necessarily closed and may conduct in part by means of an
electric field (displacement current).
Circuit, Earth (Ground) Return. An electric circuit in which the
ground serves to complete a path for charge flow.
Circuit, Magnetic. A closed path for establishment of magnetic flux
(magnetic field) that has the direction of the magnetic induction
at every point.
Cleat. An assembly of a pair of insulating material members with
grooves for holding one or more conductors at a definite distance
from the mounting surface.
Clip, Fuse. Contacts on a fuse support for connecting a fuse holder
into a circuit.
Closed-Circuit Voltage. The terminal voltage of a source of electricity
under a specified current demand.
Closed Electric Circuit. A continuous path or paths providing for
charge flow. In an ac closed circuit, charge flow may be changed
into displacement current through a capacitor (condenser).
Coercive Force. The magnetizing force at which the magnetic induction
is zero at a point on the hysteresis loop of a magnetic
substance.
Coil. A conductor arrangement (basically a helix or spiral) that concentrates
the magnetic field produced by electric charge flow.
Composite Conductor. A conductor consisting of two or more
strands of different metals, operated in parallel.
Concealed. To be made inaccessible by the structure or finish of a
building; also, wires run in a concealed raceway.
Condenser. Also termed capacitor; a device that stores electric
charge by means of an electric field.
Conductance. A measure of permissiveness to charge flow; the reciprocal
of resistance.
Conductor. A substance that has free electrons or other charge carriers
that permit charge flow when an emf is applied across the
substance.
Conduit. A structure containing one or more ducts; commonly
formed from iron pipe or electrical metallic tubing (EMT).
Conduit Fittings. Accessories used to complete a conduit system,
such as boxes, bushings, and access fittings.
Conduit, Flexible Metal. A flexible raceway of circular form for enclosing
wires or cables; usually made of steel wound helically and
with interlocking edges and a weather-resistant coating. Sometimes
called Greenfield.
Conduit, Rigid Steel. A raceway made of mild steel pipe with a
weather-resistant coating.
Conduit Run. A duct bank; an arrangement of conduit with a continuous
duct between two points in an electrical installation.
Contactor. An electric power switch, not operated manually, designed
for frequent operation.
Contacts. Conducting parts that employ a junction that is opened
or closed to interrupt or complete a circuit.
Control Relay. A relay used to initiate or permit a predetermined
operation in a control circuit.
Coulomb. An electric charge of 6.28 × 1018 electrons. One coulomb
is transferred when a current of one ampere continues past a point
for one second.
Counter EMF. CEMF; the effective emf within a system which opposes
current in a specified direction.
Current. The rate of charge flow. A current of one ampere is equal
to a flow rate of one coulomb per second.
Cycle. The complete series of values that occurs during one period
of a periodic quantity. The unit of frequency, the hertz, is equal
to one cycle per second.
Dead. Functionally conducting parts of an electrical system that
have no potential difference or charge (voltage of zero with respect
to ground).
Degree, Electrical. An angle equal to 1/360 of the angle between
consecutive field poles of like polarity in an electrical machine.
Diagram, Connection. A drawing showing the connections and interrelations
of devices employed in an electrical circuit.
Dielectric. A medium or substance in which a potential difference
establishes an electric field that is subsequently recoverable as
electric energy.
Direct Current. Aunidirectional current with a constant value. Constant
value is defined in practice as a value that has negligible
variation.
Direct EMF. Also termed direct voltage; anemf that does not change
in polarity and has a constant value (one of negligible variation).
Discharge. An energy conversion involving electrical energy. Examples
include discharge of a storage battery, discharge of a capacitor,
and lightning discharge of a thundercloud.
Displacement Current. The apparent flow of charge through a dielectric
such as in a capacitor; represented by buildup and/or decay
of an electric field.
Disruptive Discharge. A rapid and large current increase through
an insulator due to insulation failure.
Distribution Center. A point of installation for automatic overload
protective devices connected to buses where an electrical supply
is subdivided into feeders and/or branch circuits.
Divider, Voltage. A tapped resistor or series arrangement of resistors,
sometimes with movable contacts, providing a desired IR
drop. (A voltage divider is not continuously and manually variable
as in a potentiometer).
Drop, Voltage. An IR voltage between two specified points in an
electric circuit.
Duct. A single enclosed runway for conductors or cables.
Effective Value. The effective value of a sine-wave ac current or voltage
is equal to 0.707 of peak. Also called the root-mean-square
Glossary 423
(rms) value, it produces the same I 2R power as an equal dc
value.
Efficiency. The ratio of output power to input power, usually expressed
as a percentage.
Electrical Units. In the practical system, electrical units comprise the
volt, the ampere, the ohm, the watt, the watt-hour, the coulomb,
the mho, the henry, the farad, and the joule.
Electricity. A physical entity associated with the atomic structure of
matter that occurs in polar forms (positive and negative) and that
are separable by expenditure of energy.
Electrode. A conducting substance through which electric current
enters or leaves in devices that provide electrical control or energy
conversion.
Electrolyte. A substance that provides electrical conduction when
dissolved (usually in water.)
Electrolytic Conductor. Flow of electric charges to and from electrodes
in an electrolytic solution.
Electromagnetic Induction. A process of generation of emf by movement
of magnetic flux that cuts an electrical conductor.
Electromotive Force (EMF). An energy-charge relation that results
in electric pressure, which produces or tends to produce charge
flow (see Voltage).
Electron. The subatomic unit of negative electricity; it is a charge of
1.6 × 10−19 coulomb.
Electronics. The science dealing with charge flow in vacuum, gases,
and crystal lattices.
Electroplating. The electrical deposition of metallic ions as neutral
atoms on an electrode immersed in an electrolyte.
Electrostatics. A branch of electrical science dealing with the laws
of electricity at rest.
Energy. The amount of physical work a system is capable of doing.
Electrical energy is measured in watt-seconds (the product of
power and time).
Entrance, Duct. An opening of a duct at a distributor box or other
accessible location.
Equipment, Service. A circuit breaker or switches and fuses with
their accessories, installed near the point of entry of service conductors
to a building.
424 Glossary
Exciter. An auxiliary generator for supplying electrical energy to the
field of another electrical machine.
Farad. A unit of capacitance defined by the production of one volt
across the capacitor terminals when a charge of one coulomb is
stored.
Fault Current. An abnormal current flowing between conductors or
from a conductor to ground due to an insulation defect, arc-over,
or incorrect connection.
Feeder. A conductor or a group of conductors for connection of generating
stations, substations, generating stations and substations,
or a substation and a feeding point.
Ferromagnetic Substance. A substance that has a permeability considerably
greater than that of air;