电气英语证书考试(PEC)-基础电气工程术语和定义.doc

电气英语证书考试(PEC)-Basic Electrical engineering terms and definitionsAccess Fitting. A fitting that permits access to conductors in concealedor enclosed wiring, elsewhere than at an outlet.Active Electrical Network. A network that contains one or moresources of electrical energy.Admittance. The reciprocal of impedance.Air-Blast Transformer. A transformer cooled by forced circulationof air through its core and coils.Air Circuit Breaker. A circuit breaker in which the interruption occursin air.Air Switch. A switch in which the interruption of the circuit occursin air.Alive. Electrically connected to a source of emf, or electricallycharged 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 whichover a period is zero.Alternator. Synchronous generator; a synchronous alternating currentmachine that changes mechanical power into electricalpower.Ambient Temperature. The temperature of a surrounding coolingmedium, such as gas or liquid, that comes into contact with theheated 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 apparatusthat indicates whether a current is flowing or has flowed in oneor more circuits.Apparent Power. In a single-phase, two-wire circuit, the product ofthe effective current in one conductor multiplied by the effectivevoltage between the two points of entry.Appliance. Current-consuming equipment, fixed or portable, suchas heating or motor-operated equipment.Arc-Fault Circuit Interrupter (AFCI). An electrical device that detectsthe unique electronic characteristics of electrical arcs. If anarc is sensed, the device further deenergizes the circuit to which itis connected.Arcing Contacts. Contacts on which an arc is drawn after the maincontacts of a switch or circuit breaker have parted.Arcing Time of Fuse. The time elapsing from the severance of thefuse link to the final interruption of the circuit under specifiedconditions.Arc-Over of Insulator. A discharge of power current in the form ofan arc, following a surface discharge over an insulator.Armor Clamp. A fitting for gripping the armor of a cable at thepoint where the armor terminates, or where the cable enters ajunction box or other apparatus.Armored Cable. A cable provided with a wrapping of metal, usuallysteel wires, primarily for the purpose of mechanical protection.Arrester, Lightning. A device that reduces the voltage of a surgeapplied to its terminals and restores itself to its original operatingcondition.Autotransformer. A transformer in which part of the winding iscommon to both the primary and secondary circuits.Back-Connected Switch. A switch in which the current-carryingconductors are connected to studs in back of the mounting base.Bank. An assemblage of fixed contacts in a rigid unit over whichwipers or brushes may move and make connection with thecontacts.Bank, Duct. An arrangement of conduit that provides one or morecontinuous ducts between two points.Benchboard. A switchboard with a horizontal section for controlswitches, indicating lamps, and instrument switches; may alsohave a vertical instrument section.Bidirectional Current. A current that has both positive and negativevalues.Bond, Cable. An electrical connection across a joint in the armoror 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 forinstallation of wiring, making connections, or mounting devices.Box, Junction. An enclosed distribution panel for connection orbranching of one or more electric circuits without making permanentsplices.Box, Junction (Interior Wiring). A metal box with blank cover forjoining runs of conduit, electrical metallic tubing, wireway, orraceway and for providing space for connection and branching ofenclosed conductors.Box, Pull. A metal box with a blank cover which is used in a run ofconduit or other raceway to facilitate pulling in the conductors; itmay also be installed at the end of one or more conduit runs fordistribution of the conductors.Branch Circuit. That portion of a wiring system extending beyondthe final automatic overload protective device.Branch Circuit, Appliance. A circuit supplying energy either to permanentlywired appliances or to attachment-plug receptacles suchas appliance or convenience outlets and having no permanentlyconnected lighting fixtures.Branch Circuit Distribution Center. A distribution circuit at whichbranch circuits are supplied.Branch Circuit, Lighting. A circuit supplying energy to lighting outletsonly.Branch Conductor. A conductor that branches off at an angle froma continuous run of conductor.Break. The break of a circuit-opening device is the minimum distancebetween the stationary and movable contacts when the deviceis in its open position.Breakdown. Also termed puncture, denoting a disruptive dischargethrough insulation.Breaker, Line. A device that combines the functions of a contactorand a circuit breaker.Buried Cable. A cable installed under the surface of the soil in sucha 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 commonconnection for three or more circuits in a switchgearassembly.Bushing. Also termed insulating bushing; a lining for a hole for insulationand/or protection from abrasion of one or more conductorspassing through it.Cabinet. An enclosure for either surface or flush mounting, providedwith a frame, mat, or trim.Cable. The package of wires, insulating material, sheathing, andwhatever else is necessary for the type being installed. It is usuallypurchased in large spools.Cable Fault. A partial or total local failure in the insulation or continuityof the conductor.Cable Joint. Also termed a splice; a connection between twoor more individual lengths of cables, with their conductorsindividually connected, and with protecting sheaths over thejoint.Cable, Service. Service conductors arranged in the form of a cable(see Service).Cable Sheath. The protective covering, such as lead or plastic, appliedover a cable.Charge, Electric. An inequality of positive and negative electricityin or on a body. The charge stored in a capacitor (condenser)corresponds to a deficiency of free electrons on the positiveplate and to an excess of free electrons on the negativeplate.Choke Coil. A low-resistance coil with sufficient inductance to substantiallyimpede ac or transient currents.Circuit, Electric. A conducting path through which electric chargesmay flow. A dc circuit is a closed path for charge flow; an ac circuitis not necessarily closed and may conduct in part by means of anelectric field (displacement current).Circuit, Earth (Ground) Return. An electric circuit in which theground 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 inductionat every point.Cleat. An assembly of a pair of insulating material members withgrooves for holding one or more conductors at a definite distancefrom the mounting surface.Clip, Fuse. Contacts on a fuse support for connecting a fuse holderinto a circuit.Closed-Circuit Voltage. The terminal voltage of a source of electricityunder a specified current demand.Closed Electric Circuit. A continuous path or paths providing forcharge flow. In an ac closed circuit, charge flow may be changedinto displacement current through a capacitor (condenser).Coercive Force. The magnetizing force at which the magnetic inductionis zero at a point on the hysteresis loop of a magneticsubstance.Coil. A conductor arrangement (basically a helix or spiral) that concentratesthe magnetic field produced by electric charge flow.Composite Conductor. A conductor consisting of two or morestrands of different metals, operated in parallel.Concealed. To be made inaccessible by the structure or finish of abuilding; also, wires run in a concealed raceway.Condenser. Also termed capacitor; a device that stores electriccharge by means of an electric field.Conductance. A measure of permissiveness to charge flow; the reciprocalof resistance.Conductor. A substance that has free electrons or other charge carriersthat permit charge flow when an emf is applied across thesubstance.Conduit. A structure containing one or more ducts; commonlyformed 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 enclosingwires or cables; usually made of steel wound helically andwith interlocking edges and a weather-resistant coating. Sometimescalled Greenfield.Conduit, Rigid Steel. A raceway made of mild steel pipe with aweather-resistant coating.Conduit Run. A duct bank; an arrangement of conduit with a continuousduct between two points in an electrical installation.Contactor. An electric power switch, not operated manually, designedfor frequent operation.Contacts. Conducting parts that employ a junction that is openedor closed to interrupt or complete a circuit.Control Relay. A relay used to initiate or permit a predeterminedoperation in a control circuit.Coulomb. An electric charge of 6.28 1018 electrons. One coulombis transferred when a current of one ampere continues past a pointfor one second.Counter EMF. CEMF; the effective emf within a system which opposescurrent in a specified direction.Current. The rate of charge flow. A current of one ampere is equalto a flow rate of one coulomb per second.Cycle. The complete series of values that occurs during one periodof a periodic quantity. The unit of frequency, the hertz, is equalto one cycle per second.Dead. Functionally conducting parts of an electrical system thathave no potential difference or charge (voltage of zero with respectto ground).Degree, Electrical. An angle equal to 1/360 of the angle betweenconsecutive field poles of like polarity in an electrical machine.Diagram, Connection. A drawing showing the connections and interrelationsof devices employed in an electrical circuit.Dielectric. A medium or substance in which a potential differenceestablishes an electric field that is subsequently recoverable aselectric energy.Direct Current. Aunidirectional current with a constant value. Constantvalue is defined in practice as a value that has negligiblevariation.Direct EMF. Also termed direct voltage; anemf that does not changein polarity and has a constant value (one of negligible variation).Discharge. An energy conversion involving electrical energy. Examplesinclude discharge of a storage battery, discharge of a capacitor,and lightning discharge of a thundercloud.Displacement Current. The apparent flow of charge through a dielectricsuch as in a capacitor; represented by buildup and/or decayof an electric field.Disruptive Discharge. A rapid and large current increase throughan insulator due to insulation failure.Distribution Center. A point of installation for automatic overloadprotective devices connected to buses where an electrical supplyis subdivided into feeders and/or branch circuits.Divider, Voltage. A tapped resistor or series arrangement of resistors,sometimes with movable contacts, providing a desired IRdrop. (A voltage divider is not continuously and manually variableas in a potentiometer).Drop, Voltage. An IR voltage between two specified points in anelectric circuit.Duct. A single enclosed runway for conductors or cables.Effective Value. The effective value of a sine-wave ac current or voltageis equal to 0.707 of peak. Also called the root-mean-squareGlossary 423(rms) value, it produces the same I 2R power as an equal dcvalue.Efficiency. The ratio of output power to input power, usually expressedas a percentage.Electrical Units. In the practical system, electrical units comprise thevolt, 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 ofmatter that occurs in polar forms (positive and negative) and thatare separable by expenditure of energy.Electrode. A conducting substance through which electric currententers or leaves in devices that provide electrical control or energyconversion.Electrolyte. A substance that provides electrical conduction whendissolved (usually in water.)Electrolytic Conductor. Flow of electric charges to and from electrodesin an electrolytic solution.Electromagnetic Induction. A process of generation of emf by movementof magnetic flux that cuts an electrical conductor.Electromotive Force (EMF). An energy-charge relation that resultsin electric pressure, which produces or tends to produce chargeflow (see Voltage).Electron. The subatomic unit of negative electricity; it is a charge of1.6 1019 coulomb.Electronics. The science dealing with charge flow in vacuum, gases,and crystal lattices.Electroplating. The electrical deposition of metallic ions as neutralatoms on an electrode immersed in an electrolyte.Electrostatics. A branch of electrical science dealing with the lawsof electricity at rest.Energy. The amount of physical work a system is capable of doing.Electrical energy is measured in watt-seconds (the product ofpower and time).Entrance, Duct. An opening of a duct at a distributor box or otheraccessible location.Equipment, Service. A circuit breaker or switches and fuses withtheir accessories, installed near the point of entry of service conductorsto a building.424 GlossaryExciter. An auxiliary generator for supplying electrical energy to thefield of another electrical machine.Farad. A unit of capacitance defined by the production of one voltacross the capacitor terminals when a charge of one coulomb isstored.Fault Current. An abnormal current flowing between conductors orfrom 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 generatingstations, substations, generating stations and substations,or a substation and a feeding point.Ferromagnetic Substance. A substance that has a permeability considerablygreater than that of air; a