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381 Cards in this Set

  • Front
  • Back
AC EXCITER
An exciter that produces alternating current; also called an alterex.
AIR CIRCUIT BREAKER
A circuit breaker in which the interruption occurs in air.
The air space between two magnetically or electrically related objects
AIR GAP
A switch in which the interruption of the circuit occurs in air. Same as air circuit breaker (ACB)
AIR SWITCH
A relay, other than an annunciator, used to operate, or to operate in connection with, visual or audible alarm
ALARM RELAY
To adjust the tuned circuits of a receiver or transmitter for maximum
signal response
ALIGN
The adjustment of tuned circuits in a receiver to obtain the desired frequency response, and the synchronization of components in a system.
ALIGNMENT
Emitter to collector current changes in a transistor
ALPHA
A flow of electricity that reaches
a maximum value in one direction, then reverses itself and reaches a
maximum value in the opposite direction. That process is repeated at regular intervals.
ALTERNATING CURRENT (AC)
One half cycle, either when alternating current goes from a
starting value, travels to the maximum value in one direction, then travels back to the starting value. Or travels the opposite direction, and follows the reverse course. Two of these make one cycle.
ALTERNATION
A permanently short-circuited winding, usually uninsulated, so arranged as to oppose rotation or pulsation of the magnetic field with respect to the pole shoes.
AMORTISSEUR WINDING (DAMPER WINDING)
A unit of electrical current or rate of flow of electrons
AMPERE
A current of one ampere flowing for one hour
AMPERE HOUR
The magnetomotive force produced by a coil, derived by multiplying the number of turns of a wire in the coil by the current (in amperes) flowing through it
AMPERE-TURNS
A device that automatically controls generator field voltage.
AMPLIDYNE
increase in size of a medium in its transmission from one point to another
AMPLIFICATION
A device which draws power from a source other than the input signal and which produces as an output an enlarged reproduction of the essential features of its input.
AMPLIFIER
The magnitude of variation in a changing quantity from its
zero value. The word must be modified with an adjective such as peak, rms, maximum, etc., which designates the specific amplitude in question.
AMPLITUDE
In an amplifier or other device, that which occurs when the output amplitude is not a linear function of the input ampIitude.
AMPLITUDE DISTORTION
A visual device consisting of a number of pilot lights or drops. Each light or drop indicates the condition which exists or has existed in an associated circuit and is labeled accordingly.
ANNUNCIATOR
ANODE
The positive electrode
Special contacts on which the arc is drawn after the main contacts of a switch or circuit breaker have parted.
ARCING CONTACTS
Any frequency corresponding to a normally audible sound wave. These frequencies range roughly from 20 to 20,000 cycles per second.
AUDIO FREQUENCY
A self-acting compensation device which maintains the output of a transmission system constant within narrow limits in the face of wide variations in the attenuation of the system.
AUTOMATIC GAIN CONTROL
A transformer with a single winding (electrically) in which the whole winding acts as the primary winding, and only part of the winding acts as the secondary (step-down); or part of the winding acts as the primary and the whole winding acts as the secondary (step-up).
AUTOTRANSFORMER
A relay which responds to the opening or closing of its operating circuit, to assist relay or device in the performance
of a function.
AUXILIARY RELAY
The angular measurement in a horizontal plane and in a clockwise
direction, beginning at a point oriented to north.
AZIMUTH
Any range of frequencies which lies between two defined
BAND
The range within the limits of a band
BANDWIDTH
The minimum load over a given period of time
BASE LOAD
One of the two additional frequencies produced when two different frequencies are combined. One of this frequency is the sum of the two original frequencies; the other is the difference between
them.
BEAT FREQUENCY
A switchboard having a horizontal or
slightly inclined section for mounting control switches, indicating lamps and instrument switches, and constructed with or without vertical instrument sections.
BENCHBOARD (CONTROL DESK)
The difference between the base current and the collector current in a
transistor
BETA
The electrical, mechanical, or magnetic force applied to a relay,
vacuum tube, or other device for the purpose of establishing an
electrical or mechanical reference level for the operation of the
device.
BIAS
A resistance used to produce the voltage drop necessary to provide a desired biasing voltage.
BIAS RESISTOR
A resistance connected in parallel with a power supply output to protect equipment from excessive voltages if the load is removed or substantially reduced; improve the voltage regulation, and to drain the charge remaining in the filter capacitors when the unit is turned off.
BLEEDER RESISTOR
Load held steadily at a fixed point.
BLOCKED LOAD
A capacitor used to block the flow of direct current while permitting the flow of alternating current
BLOCKING CAPACITOR
Small toggle or knife switches used to isolate control circuits from apparatus
BLOCKING SWITCH
Raise or attempt to raise voltage
BOOST
The voltage at which an insulator or dielectric ruptures, or at which ionization and conduction take place in a gas or a vapor. The voltage required to jump an air gap.
BREAK-DOWN VOLTAGE
The conducting material, usually made of carbon, rides on the
commutator or slip rings through which the current flows in or out of
the rotor of the machine
BRUSH
A device which holds the brush in position
BRUSH HOLDER
An exciter that does not have brushes or slip rings
BRUSHLESS EXCITER
Lower or attempt to lower voltage
BUCK
The term used to specify an uninsulated conductor (a bar or wire); may be solid, hollow, square, or round. Used to carry heavy currents or to make a common connection between several circuits.
BUS
A capacitor used to provide an alternating current path of comparatively low impedance around a circuit element
BYPASS CAPACITOR
The property of two or more bodies which enables them to store electrical energy in an electrostatic field between the bodies.
CAPACITANCE
A method of transferring energy from one circuit to another by means of a capacitor that is common to both circuits.
CAPACITIVE COUPLING
Two electrodes or sets of electrodes in the form of plates, separated from each other by an insulating material called the dielectric.
CAPACITOR
The ratio of the average load on a machine or equipment for the period of time considered, compared to the rating of the machine or equipment.
FACTOR
A wave of constant amplitude, frequency, and phase which can be modulated by changing amplitude, frequency, or phase.
CARRIER
High-frequency alternating current superimposed on ordinary telephone, telegraph, or power-line frequencies. The carrier may be modulated with voice signals for telephone communications between
points in a power system, or it may be tone modulated to operate switching relays or transmit data.
CARRIER CURRENT
The negative electrode.
CATHODE
A coherent system of units for expressing the magnitude of electrical and magnetic quantities. The most common fundamental units of these quantities are the centimeter, gram, and second.
CGS ELECTROMAGNETIC SYSTEM OF UNITS
The current that flows into the capacitance of a transmission line when voltage is applied at its terminals.
CHARGING CURRENT OF A TRANSMISSION LINE
An inductance used to impede the flow of pulsating direct current or alternating current by means of its self-inductance.
CHOKE
A device for interrupting a circuit under normal or abnormal conditions by means of separable contacts.
CIRCUIT BREAKER
An assembly of levers and other
parts which actuates the moving contacts of the circuit breaker.
CIRCUIT BREAKER MECHANISM
An area equal to that of a circle with a diameter of 0.001 inch. It is used to define the cross sectional areas.
CIRCULAR MIL
A coil used in the electromagnet which supplies power for closing a circuit breaker.
CLOSING COIL OF A CIRCUIT BREAKER
A semiconductor device made from metal-oxide materials. These devices are used in harsh environments, or where incompatible circuits must be
made compatible. They operate under a wide variety of definable
conditions.
CMOS (COMPLIMENTARY METALOXIDE SEMICONDUCTOR)
Metal rings suitably mounted
on the rotating member of an electric machine, serving through stationary brushes bearing thereon, to conduct current into or out of the rotating member.
COLLECTOR RINGS (SLIP RINGS)
That part of the rotor of a motor or generator which is used to conduct electrical energy to the rotor windings from the stationary brushes with which the commutator is in contact.
COMMUTATOR
To provide a means of counteracting.
COMPENSATE
Obsolete term for capacitor.
CONDENSER
The ability with which a substance transmits heat or electricity.
CONDUCTIVITY
A material (usually a metal) that conducts electricity through the transfer of orbital electrons.
CONDUCTOR
An auxiliary tank, normally only partly filled with oil or other cooling liquid and connected to the completely filled main tank.
CONSERVATOR OR EXPANSION TANK
A device for the purpose of repeatedly establishing or interrupting an electric power circuit.
CONTACTOR
A bus mounted in the rear of a switchboard or in the circuit breaker structure to distribute power for operating electrically controlled devices.
CONTROL BUS
A circuit carrying a low voltage used to operate various pieces of equipment such as circuit breakers, contactors, valves, etc., usually from a remote location.
CONTROL CIRCUIT
Direct current applied to magnetic coils to cause variation of output voltage.
CONTROL FIELD
A switch for controlling electrically operated devices.
CONTROL SWITCH
A magnetic material placed within a coil to intensify the magnetic field. Magnetic material inside a relay or coil winding.
CORE
A luminous discharge of electricity, due to ionization of the air, appearing on the surface of a conductor when the potential gradient exceeds a certain value (corona always precedes dielectric breakdown).
CORONA
The effect produced when two wires, or other conductors having a great difference of voltage, are placed near each other.
CORONA EFFECT
A voltage developed in an inductive circuit by an alternating or pulsating current. The polarity of this voltage is at every instant opposite that of the applied voltage.
COUNTERELECTROMOTIVE FORCE
The effect produced in the primary winding of a transformer by the current flowing in the secondary winding.
COUPLED IMPEDANCE
The association of two circuits in such a way that power may be transferred from one to the other.
COUPLING
IC whose functions are to receive, process, and transmit data provided from an outside source.
CPU (CENTRAL PROCESSING UNIT)
That part to which the moving contact
rods of a circuit breaker are attached.
CROSS HEAD (CROSSBAR)
-(1) A natural substance, such as quartz or tourmaline, which is capable of producing a voltage stress when under pressure, or producing pressure when under an applied voltage. Under stress it has the property of responding only to a given frequency when cut to a given
thickness.
(2) A nonlinear element such as galena or silicon in which case the piezoelectric characteristic is not exhibited.
CRYSTAL (XTAL)
A device which employs the nonlinear characteristic of a crystal (non-piezoelectrictype) and a point contact to mix two frequencies.
CRYSTAL MIXER
An oscillator circuit in which a piezoelectric crystal is used to control the frequency and to reduce frequency instability to a minimum.
CRYSTAL OSCILLATOR
A transformer, intended for measuring or control purposes, designed to have its primary winding connected in series with a circuit carrying the current to be measured or controlled.
(Never open the secondary circuit of a current transformer when the
primary is energized.)
CURRENT TRANSFORMER
A resistor inserted in an electric
circuit to limit the flow of current to some predetermined value.
NOTE: A current-limiting resistor, usually in series with a fuse or
circuit breaker, may be employed to limit the flow of circuit or system
energy at the time of a fault or short-circuit.
CURRENT-LIMITING RESISTOR
The change of an alternating wave from a starting value negative to
a peak then return through the starting value to a positive peak and back to the starting value.
CYCLE
A dc galvanometer consisting of
a narrow rectangular coil suspended between the poles of a permanent
magnet.
D’ARSONVAL GALVANOMETER
An exciter that produces direct current for the rotor windings of a main generator.
DC EXCITER
Also called detection. The operation on a previously modulated wave in such a way that it will have substantially the same
characteristics as the original modulating wave.
DEMODULATION /DETECTION
A device which operates on a carrier wave to recover the wave with which the carrier was originally modulated.
DEMODULATOR
An insulator; a term applied to the insulating material between the plates of a capacitor.
DIELECTRIC
The ratio of the capacitance of a capacitor with a dielectric between the electrodes to the capacitance with air between the electrodes.
DIELECTRIC CONSTANT
A semiconductor used to limit electric flow to one direction only.
DIODE
Current that travels from the positive node of a voltage source, through the electrical circuits and back to the voltage source through the negative node. The current always travels in the same direction and is usually at a fixed level. NOTE: This direction of flow
is from electrical theories. The reverse is true using scientific theories.
DIRECT CURRENT (DC)
A switch that, in most cases, is operated to isolate a circuit after the circuit breaker has been opened; usually not designed to open under load.
DISCONNECT SWITCH
Any capacitance not concentrated
within a capacitor, such as the capacitance that exists between the turns in a coil or choke, or between adjacent conductors of a circuit.
DISTRIBUTED CAPACITANCE
The inductance along the entire length of a conductor, as distinguished from the inductance concentrated within a coil.
DISTRIBUTED INDUCTANCE
A resistor used to decrease a given voltage by an amount equal to the potential drop across the resistor.
DROPPING RESISTOR
An electrolytic capacitor using
a paste instead of liquid electrolyte.
DRY ELECTROLYTIC CAPACITOR
The equivalent heating value of an alternating
current or voltage, as compared to a direct current or voltage. It is 0.707 times the peak value of a sine wave. It is also called the
RMS value.
EFFECTIVE VALUE
Ratio of the useful output of a physical quantity which may be stored, transferred, or transformed by a device, to the total input of the device.
EFFICIENCY
A space in which an electric charge will experience a force exerted upon it.
ELECTRIC FIELD
A machine which transforms mechanical power into electrical power.
ELECTRIC GENERATOR
Of a switch or circuit breaker is power
operation by electricity.
ELECTRICAL OPERATION
A terminal at which electricity passes from one medium into
another or the terminal by which a current leaves or enters an electrolytic cell.
ELECTRODE
A solution of a substance which is capable of conducting electricity. An electrolyte may be in the form of either a liquid or a paste.
ELECTROLYTE
A capacitor employing a metallic plate and an electrolyte as the second plate separated by a dielectric which is produced by electrochemical action.
ELECTROLYTIC CAPACITOR
A temporary magnet consisting of a solenoid with an iron core. A magnetic field exists only while current flows through the solenoid.
ELECTROMAGNET
The field of influence produced around
a conductor by the current flowing through it.
ELECTROMAGNETIC FIELD
The force which causes electricity
to flow when there is a difference of potential between two points.
ELECTROMOTIVE FORCE (EMF)
One of the natural elementary constituents of matter; it carries
a negative electric charge of one electronic unit.
ELECTRON
The freeing of electrons from a body into space under the influence of heat, light, impact, chemical disintegration, or potential difference.
ELECTRON EMISSION
A bus having its conductors enclosed in an insulating or metal enclosure.
ENCLOSED BUS
Current flow that causes magnetic field.
EXCITATION
An auxiliary generator that provides field current for an alternating
current generator.
EXCITER
The capacitance of a capacitor.
FARAD
A partial or total local failure in the insulation or continuity of a
conductor.
FAULT
Electrical flow usually from the output of a device back to
its input. Used for stabilizing, measurement, amplifying, etc.
FEEDBACK
A conductor or group of conductors connecting (a) two generating
stations, (b) two substations, (c) a generating station and a substation or feeding point, or (d) a substation and a feeding point.
FEEDER
A transistor designed such
that the control voltage, usually applied to the junction called the
gate, restricts the current passage as the applied voltage is increased.
This is in opposition to the way the original transistors controlled
current.
FET (FIELD EFFECT TRANSISTOR)
System to transmit data by light.
FIBER OPTICS
The region around magnet or electric charge in which the magnet or charge is capable of exerting its influence.
FIELD
A coil of insulated wire to be mounted on a field pole to magnetize it.
FIELD COIL
magnet used to produce a magnetic field.
FIELD MAGNET
A combination of circuit elements designed to pass a definite range of frequencies, attenuating all others.
FILTER
The power intended to be always available even under emergency conditions.
FEW POWER
A bias voltage of constant value, such as one obtained from a battery, power supply, or generator.
FIXED BIAS
A capacitor which has no provision for varying its capacitance.
FIXED CAPACITOR
A resistor which has no provision for varying its resistance.
FIXED RESISTOR
The magnetic lines of force existing between two opposite magnetic
poles.
FLUX
The supporting structure for the stator parts.
FRAME
Electrons which are loosely held and consequently tend to move at random among the atoms of the material.
FREE ELECTRONS
Oscillatory currents which continue to flow in a tuned circuit after the impressed voltage has been removed. Their frequency is the resonant frequency of the tuned circuit.
FREE OSCILLATIONS
The number of complete cycles per second existing in any form of wave motion; such as the number of cycles per second of an alternating current. See Hertz.
FREQUENCY
The regulation of the frequency of a generating station or system within a narrow range.
FREQUENCY CONTROL
A machine which converts the power of an alternating-current system from one frequency to another, with or without a change in the number of phases, or in the voltage.
FREQUENCY CONVERTER
A circuit which utilizes both the positive and the negative alternations of an alternating current to produce a direct current.
FULL-WAVE RECTIFIER CIRCUIT
A part of a circuit made of low melting point material so that it will melt and break the circuit when a specified current is exceeded.
FUSE
instrument for measuring an electric current.
GALVANOMETER
A plant wherein electric energy is produced from some form of energy (e.g. chemical, mechanical, or hydraulic) by means of suitable apparatus.
GENERATING STATION
A machine that transforms mechanical energy into electrical energy.
GENERATOR
A regulator which functions to maintain the voltage of a synchronous generator,
condenser, motor, or of a direct-current generator, at a predetermined value, or vary it according to a predetermined value, or vary it according to a predetermined plan.
GENERATOR VOLTAGE REGULATOR
A bus used to connect a number of grounding conductors to one or more grounding electrodes.
GROUND BUS
An instrument used for indicating the presence of a ground on an ungrounded system.
GROUND DETECTOR
A circuit in which one conductor or point is intentionally grounded.
GROUNDED CIRCUIT
A system of conductors in which at least one conductor or point (usually the middle wire or neutral point of transformer of generator windings) is intentionally grounded either solidly or through a current-limiting device.
GROUNDED SYSTEM
A form of air switch by means of which a circuit or a piece of apparatus may be connected to ground.
GROUNDING SWITCH
A transformer intended primarily for the purpose of providing a neutral point for ground purposes.
GROUNDING TRANSFORMER
The process of rectifying an alternating current wherein only one-half of the input cycle is passed and the other half is blocked by the action of the rectifier, thus producing pulsating direct current.
HALF-WAVE RECTIFICATION
A sinusoidal wave having a frequency that is an integral multiple of the fundamental frequency.
HARMONIC
An element that supplies the heat to an indirectly heated cathode. A resistor that converts electrical energy into heat.
HEATER
The basic unit of inductance.
HENRY
Replaces cycle(s) per second as the basic unit of frequency.
HERTZ
To mix two frequencies together in order to produce two other frequencies equal to the sum and difference of the first two.
HETERODYNE
The higher voltage electrical system of two systems connected by a transformer.
HIGH SIDE
HIGH VOLTAGE is above...
... 600 volts.
The total resistance offered by a
device in a high-frequency ac circuit.
HIGH-FREQUENCY RESISTANCE
A test for determining the breakdown point of insulating materials and spacings.
HIGH-POTENTIAL TEST (High Pot)
Energized electrically -referring to pieces of electrical equipment, buses or lines.
HOT
A turbine installed to provide a source of auxiliary power.
HOUSE TURBINE
An instrument used to measure the specific gravity of liquids.
HYDROMETER
The amount the magnetization of a ferrous substance lags the magnetizing force because of molecular friction.
HYSTERESIS
Any electronic device in which both
active and passive devices are present in the same package.
IC (INTEGRATED CIRCUIT)
The total opposition offered to the flow of an alternating current. It may consist of any combination of resistance, inductive reactance, and capacitive reactance.
IMPEDANCE (Z)
A method of coupling using an impedance as the coupling device, common to both the primary and secondary circuits.
IMPEDANCE COUPLING
Any force acting over a comparatively short period of time, such as a momentary rise in voltage.
IMPULSE
Two waves of the same frequency that pass through their maximum
and minimum values of like polarity at the same instant, are said to be ...
IN PHASE
Produced by the influence of an electric or magnetic field.
INDUCED
The property of a circuit which tends to oppose a change in the existing current.
INDUCTANCE Q
The establishment of an electric charge or a magnetic field in a
substance by the proximity of an electrified source, a magnet, or a magnetic field.
INDUCTION
A device for changing direct current into high-voltage alternating current.
INDUCTION COIL
An induction machine, driven above
synchronous speed by an external source mechanical power.
INDUCTION GENERATOR
The opposition to the flow of alternating or pulsating current caused by the inductance of a circuit. It is measured ohms.
INDUCTIVE REACTANCE (XL)
A circuit element designed so that its inductance is its most important electical property; a coil.
INDUCTOR
Equipment provided to maintain an inert gas usually nitrogen, above the oil surface.
INERT GAS EQUIPMENT
The magnitude at any particular
instant when a value is continually varying with respect to time.
INSTANTANEOUS VALUE
A switch used to disconnect an
instrument or to transfer it from one circuit or phase to another.
EXAMPLES: Ammeter switch; voltmeter switch.
INSTRUMENT SWITCH
A transformer which reproduces,
in its secondary circuit, the primary current (or voltage) with its
phase relationship substantially preserved, suitable for utilization
in measurement, control or protective devices.
INSTRUMENT TRANSFORMER
An electrical or mechanical arrangement that prevents
one operation or sequence of operations from taking place until another prerequisite operation or condition has been satisfied.
INTERLOCK
A frequency to which a signal
wave is shifted locally as an intermediate step in transmission or reception.
INTERMEDIATE FREQUENCY (IF)
The resistance at zero degree centrigrade of a column of mercury of uniform cross-section having a length of 106.3 centimeters and a mass of 14.45 grams.
INTERNATIONAL OHM
A magnetically operated device used for rapidly and periodically opening and closing an electric circuit in doorbells and buzzers and in the primary circuit of a transformer supplied from a dc source.
INTERRUPTER
An electrically charged atom or group of atoms. Positively charged
Ions have a deficiency of electrons, and negatively charged ions have
surplus electrons.
ION
The dissociation of an atom or molecule into electrons and/or ions.
IONIZATION
The energy, expressed in electronvolts, needed to remove one electron from a neutral atom or molecule in its grounded state.
IONIZATION POTENTIAL
One Thousand = 1000 Watts
KILO (K)
1000 cycles; generally interpreted 'as meaning 1000 cycles per second.
KILOCYCLE (KC)
The equivalent energy supplied by a power of 1000 watts for one hour.
KILOWATT HOUR
The displacement in time, expressed in electrical degrees, between two waves of the same frequency. The lagging wave follows the leading wave.
LAG
The opposite of lag. Also, a wire or connection, to or from circuit
element.
LEAD
Conductors to or from a piece of electrical equipment.
LEADS
Undesired flow of electricity over or through an insulator.
LEAKAGE
An electric discharge of energy from the atmosphere, one terminal of which is a cloud.
LIGHTNING
A device containing spark gaps, which allow lightning currents to flow into the earth.
LIGHTNING ARRESTER
In an electric or magnetic field, drawing an imaginary line indicating the theoretical direction and intensity of the field.
LINE OF FORCE
Means of opening an electrical conductor. Not used in normal switching procedures.
LINK
The power consumed by a machine or circuit in performing its function. The power delivered by a machine.
LOAD
The ratio of average power demand, over a stipulated period of time, to the peak or maximum demand for that same interval.
LOAD FACTOR
An oscillator used in a superheterodyne circuit to
produce a sum or difference frequency equal to the intermediate frequency of the receiver. This is done by mixing its output with the received signal.
LOCAL OSCILLATOR
A feeder which follows along a circuit and distributes the voltage more evenly at different points.
LOOP FEEDER
A device in which one or more saturable reactors are used, either alone or with other circuit elements, to obtain power gain. (megamp)
MAGNETIC AMPLIFIER
An area where magnetic forces can be detected around a permanent magnet, natural magnet, or electromagnet.
MAGNETIC FIELD
The magnetic induction in a material. An electromotive force will be induced in a conductor placed in a magnetic field whenever the magnitude of the flux changes.
MAGNETIC FLUX
An alternating current generator in which the field is supplied by a permanent magnet.
MAGNETO
The force responsible for the magnetic
flux in a magnetic circuit. It is proportional to the ampere turns.
MAGNETOMOTIVE FORCE
Of a switch or circuit breaker is operation by hand without using any other source of power.
MANUAL OPERATION
The greatest of all the demands of an installation or system which have occurred during a given period of time.
MAXIMUM DEMAND
One million hertz
MEGAHERTZ (MHz)
One million vars
MEGAVAR
One million watts
MEGAWATTS (MW)
One million ohms
MEGAOHM
One millionth of a farad which is the unit of capacity.
MICROFARAD
one thousandth, usually of an inch or an ampere.
MIL
A motor-generator combination for
converting one kind of electric power to another (e.g., alternating current to direct current). The two are mounted on a common base and their shafts are coupled together.
MOTOR-GENERATOR SET
This usually refers to a generator with the driving energy removed from the prime mover but still connected to system electrically. The generator is then acting as a motor and continues to rotate.
MOTORING
The property that exists between two current- carrying conductors when the magnetic lines of force from one link with those of the other.
MUTUAL INDUCTANCE
A conductor connected to the negative terminal of source of supply. A negative conductor is frequently used as an auxiliary return circuit in a system of electric traction.
NEGATIVE CONDUCTOR
A glass envelope filled with neon gas and containing two or more insulated electrodes.
NEON BULB
An interconnected system of transmission lines that provides
multiple connections between loads and sources of generation.
NETWORK
Also called inert gas or rare gas.
NOBLE GAS
Also called junction point, branch point, or vertex. A terminal of
any branch of a network, or a terminal common to two or more branches.
NODE
Having an output which does not rise or fall in direct proportion to the input.
NONLINEAR
The unit of electrical resistance.
OHM
The voltage across an element of a dc circuit is equal to the current in amperes through the element, multiplied by the resistance of the element in oh. Expressed mathematically as E =I X R. The
other two equations obtained by transportation are I =E/R and R =E/I.
OHM'S LAW
A circuit breaker in which the interruption occurs in oil to suppress the arc and prevent damage to the contacts.
OIL CIRCUIT BREAKER
A switch in which the interruption of the circuit occurs in oil to suppress the arc and prevent damage to the contacts.
OIL SWITCH
Indicates turbo-generator loading is
under control of the governor.
ON GOVERNOR (LOADED)
Indicates turbo-generator is at
approximately synchronous speed and is under control of the turbine
governor.
ON GOVERNOR (UNLOADED)
Synchronized and connected electrically with the system,
usually referring to the main generator.
ON THE LINE
A bus without an enclosure.
OPEN BUS
As applied to a switch or circuit breaker, is the method or mode of normal operation of that switch.
OPERATION
An electronic device which generates alternating-current power at a frequency determined by the values of certain components in
its circuits.
OSCILLATOR
Two or more waveforms that have the same shape, but do not pass through corresponding values at the same instant.
OUT OF STEP OR OUT OF PHASE
A load greater than that which an electrical device or a whole transmission system is designed to carry.
OVERLOAD
A relay designed to operate when its coil current rises above a predetermined value.
OVERLOAD RELAY
A small auxiliary switch in the control circuit of a piece of equipment usually a circuit breaker, that is operated mechanically by the circuit breaker being controlled. An "A" pallet is in the same position as the circuit breaker. A "B" pallet is in the opposite position from the circuit breaker.
PALLET SWITCH
Application of a dc voltage to the plate or grid of a tube in parallel with an ac circuit so that the dc and ac components flow in separate paths. Also called shunt feed.
PARALLEL FEED
An inductor and capacitor connected in parallel to furnish a high impedance at the frequency to which the circuit is resonant.
PARALLEL-RESONANT CIRCUIT
A board usually made of epoxy,
that has the conductors that connect the junctions of the electronic components of the circuit, permanently etched or printed on the board. Today's board may involve several layers of boards and circuits laminated together.
PCB (PRINTED CIRCUIT BOARD)
The maximum electrical power load consumed or produced by a unit or group of units in a stated period of time. It may be the maximum instantaneous load or the maximum average load over a designated interval of time.
PEAK LOAD
The maximum instantaneous value of a varying current, voltage, or power. It is equal to 1.414 times the effective value of a sine wave.
PEAK VALUE
A property of matter that indicates the ease with which it is magnetized.
PERMEABILITY
The angular relationship between current and voltage in alternating-current circuits.
PHASE
The time in electrical degrees by which one wave leads or lags another.
PHASE DIFFERENCE
The effect of producing a voltage by placing a stress, either by compression, by expansion, or by twisting, on a crystal, and, conversely, the effect of producing a siress in a crystal by applying a voltage to it.
PIEZOELECTRICITY
Small dc generator used to control the field of the main
exciter.
PILOT EXCITER
A small light usually near the control switch to indicate the
condition of the circuit being controlled.
PILOT LIGHT
One of the ends of a magnet where most of its magnetism is concentrated. One electrode of a battery. An output terminal on a switch.
POLE
A conductor connected to the positive terminal of a source of supply.
POSITIVE CONDUCTOR
POT
Potential transformer
Point where separate or overhead electrical conductors come together and run as a cable.
POT HEAD
The difference in voltage between two points of a circuit.
POTENTIAL
An instrument transformer, teh primary winding is connected in parallel with the circuit whose voltage is to be measured or controlled.
POTENTIAL TRANSFORMER
The rate of doing work or the rate of expending energy. The unit is teh watt.
POWER
The ratio of the actual power of an alternating or pulsating current, as measured by a wattmeter, to the apparent power, as indicated by ammeter and voltmeter readings. The power factor if an indicator, capacitor, or insulator is an expression of the losses.
POWER FACTOR
That part of switchgear which consists of one or more panels upon which are mounted the switching controls, meters, protective and regulatory equipment. The panel or panel supports may also carry the main switching and interrupting devices together with their connections.
POWER SWITCHBOARD
The first, in electrical order, of two or more coupled circuits, in which a change in current induces a voltage in the other or secondary circuits; such as the primary winding of a transformer.
PRIMARY CIRCUIT
A transformer winding that
carries current and normally sets up a current in one or more secondary windings.
PRIMARY WINDING OR PRIMARY
A relay, the principle function of which is to protect service from interruption or to prevent or limit damage to apparatus.
PROTECTIVE RELAY
A switch or circuit breaker that has a high contact opening speed independent of the operator.
QUICK BREAK
A system in which independent feeders branch out radially from a common source of supply.
RADIAL SYSTEM
Any frequency at which coherent electromagnetic radiation of energy is possible.
RADIO FREQUENCY (RF)
The amplification of a radio wave by a receiver before detection, or by a transmitter before radiation.
RADIO-FREQUENCY AMPLIFICATION
An air core or powdered iron core coil used to impede teh flow of radio frequency currents.
RADIO-FREQUENCY CHOKE (RFC)
The output which can be
delivered for the time specified at rated secondary voltage and rated frequency without exceeding the specified temperature limitations.
RATED KVA OF A TRANSFORMER
A rating of machine or device is a designated limit of operating characteristics based on definite conditions.
RATING
The ratio of the secondary voltage of a transformer to the primary voltage under no-load conditions, or the corresponding ratio of currents in a current transformer.
RATIO OF A TRANSFORMER (RANSFORMATION)
The opposition to the flow of alternating current.
REACTANCE (X)
Grounded through a reactance
REACTANCE GROUNDED
A physical device used primarily to introduce inductive
reactance into a circuit branch.
REACTOR
The value obtained by dividing the number 1 by a quantity.
RECIPROCAL
A device used to change alternating current into a unidirectional current.
RECTIFIER
An electromechanical device in which contacts are opened and/or closed by a variation in the conditions of one electric circuit to effect the operation of other devices in the same or another electric circuit.
RELAY
NOTE: Where relays operate in response to changes in more than one condition. all conditions should be mentioned.
The resistance of a magnetic path to the flow of magnetic lines of force through it.
RELUCTANCE
A property of conductors which determines the current produced by a given difference of potential. The practical unit is the ohm.
RESISTANCE
A device connected into an electrical circuit to introduce a
specified resistance.
RESISTOR
That condition in an alternating current circuit which exists when the capacitative reactance balances the inductive reactance.
RESONANCE
An adjustable resistor so constructed that its resistance
may be changed without opening the circuit in which it may be connected.
RHEOSTAT
RMS
Abbreviation of root mean square
Electronic storage device used to hold information used by the electronic system. This device is electronically written to once. The data is then stored on the device to be read only by the system using its stored information. The device cannot be written to by the operating system, and many cannot be written to once they have been used in any way.
ROM (READ ONLY MEMORY)
Specially wound motor-driven dc generator. Amplifies minute input changes into useable output changes.
ROTARY AMPLIFIER
The rotating member of a machine.
ROTOR
Trade name for a motor driven pilot exciter system which
uses the ac generated voltage as an index to automatically control the output of the main exciter.
ROTOTROL
A pole consisting of a separate radial projection having its own iron pole piece and its own field coil, used in the field system of a generator or motor.
SALIENT POLE
The transformer output winding where the current flow is due to inductive coupling with another coil called the primary. Low-voltage conductors of a power distribution system.
SECONDARY
The winding on the output side of a transformer.
SECONDARY WINDING
A multiposition switch that permits one or more
conductors to be connected to any of several other conductors.
SELECTOR SWITCH
The deviation created in a transistor, via feedback from the emitter to the base of the transistor.
SELF BIAS
The property that causes a counterelectromotive force
to be produced in a conductor when the magnetic field produced by the conductor collapses or expands with a change in current.
SELF-INDUCTION
An electronic conductor with resistivity between that of a metal and that of an insulator.
SEMICONDUCTOR
A circuit in which resistances or other components are
connected end to end so that the same current flows throughout the circuit.
SERIES CIRCUIT
A way of making connections so as to form a series circuit.
SERIES CONNECTION
A metallic covering used to prevent magnetic or electrostatic coupling between adjacent circuits.
SHIELDING
An abnormal connection of relatively low resistance
between two points of a circuit.
SHORT CIRCUIT
A precision low-value resistor placed across the terminals of an ammeter to increase its range.
SHUNT
A wave which can be expressed as the sine of a linear function of time, space, or both.
SINE WAVE
The tendency of alternating currents to flow near teh surface of a conductor thus being restricted to a small part of the total cross-sectional area. This effect increases the resistance and becomes more marked as the frequency rises.
SKIN EFFECT
The difference between the synchronous speed of a motor and the speed at which it operates. This may be expressed as a percent or decimal fraction of synchronous speed or directly in RPM.
SLIP
An electric conductor wound as a spiral with a small pitch,
or as two or more coaxial spirals that surrounds a moveable metal core.
SOLENOID
A trip activated by electrical inputs from various circuits
designed to protect the turbine.
SOLENOID TRIP
A circuit or equipment grounded through an adequate ground connection in which
no impedance has been inserted intentionally.
SOLIDLY GROUNDED (DIRECTLY GROUNDED
That unused generating capacity connected to the
system and ready to take load.
SPINNING RESERVE
A permanently short-circuited winding, usually uninsulated (chiefly used in induction machines), having its conductors uniformly distributed around the periphery of the machine
and joined by continuous end rings.
SQUIRREL-CAGE WINDING
The ability of a component or device to maintain its nominal
operating characteristics after being subjected to changes in temperature, environment, current, and time.
STABILITY
A fixed nonvarying condition; without motion.
STATIC
STATIC ELECTRICITY
Stationary electricity.
STATIC EXCITER
An exciter that has no moving parts.
An electrical circuit that supplies power to a plant's electrical equipment.
STATION SERVICE SYSTEM
The part of a machine which contains the stationary parts of the magnetic circuit with their associated windings.
STATOR
water cooling system that provides cooling for the stator bars in large hydrogen-cooled generators.
STATOR COOLING SYSTEM
STEP DOWN TRANSFORMER
A transformer in which the primary is the high voltage winding and the secondary is the low voltage winding.
A transformer in which the primary is the low voltage winding and the secondary is the high voltage winding.
STEP UP TRANSFORMER
A receiver in which the incoming signal is mixed with a locally generated signal to produce a predetermined
intermediate frequency.
SUPERHETERODYNE RECEIVER
SURGE
Sudden changes of current or voltage in a circuit.
The part of a cathode-ray oscilloscope which provides a
time-reference base.
SWEEP CIRCUIT
A choke with an effective inductance which varies
with the amount of current passing through it. It is used in some power- supply filter circuits.
SWINGING CHOKE
A general term covering switching, interrupting, control, metering, protecting, and regulating devices; also assemblies of these devices and associated interconnections, accessories, and supporting structures, used primarily in connection with the generation, transmission, and distribution of electric power.
SWITCH GEAR, SWITCHRACKS OR SWITCHYARDS
A manually operated apparatus at a telephone exchange. A single large panel or an assembly of panels on which are mounted the switches, circuit breakers, meters, fuses, and terminals essential to the operation of electrical equipment.
SWITCHBOARD
SYNCHRONISM
The phase relationship between two or more quantities of the some period when their phase difference is zero.
SYNCHRONOUS
Happening at the same time; having the same period and phase.
Are of similar construction to an ac generator, are capable of regulating voltage by the same methods used on generators used to consume or to produce van.
SYNCHRONOUS CONDENSER
SYNCHRONOUS GENERATOR (ALTERNATOR)
A synchronous alternating current machine which transforms mechanical power into electric power.
SYNCHROSCOPE
A device used to match a generator's output voltage
and frequency with that of the grid.
SYSTEM INTERCONNECTION
The connecting together of two or more power systems.
A supplementary device used in conjunction with a relay to
indicate that the relay has operated.
TARGET
Transmission over fairly long
distances, usually from stations to the dispatcher's office, by direct wire
or carrier current.
TELEMETRY OR TELEMETERING
A heat sensitive device located in the leads from a
circuit breaker or contactor that recognizes the heat caused by excessive current and causes the circuit to be opened.
THERMAL TRIP
THERMIONIC
Pertaining to the emission of electrons by heat.
A semiconductor whose resistance varies in a predictable manner with temperature changes.
THERMISTOR
A device for measuring temperature where two electrical conductors of dissimilar metals are joined at the point of heat application and a resulting voltage difference, directly proportional to the temperature, is developed across the free ends and is measured potentiometrically.
THERMOCOUPLE
A device which operates by means of a voltage produced by the heating effect of a current passed through the junction of two dissimiliar metals. It is used for RF measurements.
THERMOCOUPLE AMMETER
THREE PHASE GENERATOR
A generator that has three sets of stator windings and produces three outputs.
THYRISTOR
A bistable device comprising three or more junctions.
A visible line or lines appearing on the screen of a cathode-ray tube in operation.
TRACE
A device that reads raw source data, and sends a conditioned signal to a receiver for processing.
TRANSDUCER
An electric device which by electromagnetic induction
transforms electric energy from one or more circuits to one or more other circuits at the same frequency, usually with changed values of voltage and current.
TRANSFORMER
The voltage or current which exists as the result of a change from one steady-state condition to another.
TRANSIENT
TRANSISTOR
An active semiconductor having three or more junctions.
TRANSMISSION LINE
A line used for electric power transmission.
An accessory or the act of separating a piece of equipment from its source of energy.
TRIP
An electromagnet in which a moving armature trips a circuit
breaker or other protective device and thereby opens a circuit under abnormal conditions.
TRIP COIL
A mechanical or electromagnetic device used for opening (turning off) a circuit breaker or starter, either when certain abnormal electrical conditions occur or when a catch is actuated manually.
TRIPPING DEVICE
A device which operates to trip a circuit breaker, contactor, or equipment or to permit immediate tripping by other devices; or to prevent immediate reclosure of a circuit interrupter, in case it should open automatically even though its closing circuit is maintained closed.
TRIPPING RELAY -Also called trip-free relay.
This is the standard
configuration used in the design of Logic ICs. It is a fast logic circuit that utilizes transistors, as switches, in the processing of its digital logic.
TTL (TRANSISTOR-TRANSISTOR LOGIC)
A circuit consisting of inductance and capacitance
which can be adjusted for resonance at the desired frequency.
TUNED CIRCUIT
The adjustment relating to frequency of a circuit or system to secure optimum performance.
TUNING
A transmission line in which the voltages on the two conductors are not equal with respect to ground; for example, a coaxial line.
UNBALANCED LINE
One in which no point is deliberately connected to earth except through potential or ground detecting transformers or other very high impedance devices.
UNGROUNDED SYSTEM (INSULATED SUPPLY SYSTEM)
A system complete in itself. Normally not connected with
other systems.
UNIT SYSTEM
A device which uses either the amplifier characteristic or the rectifier characteristic of a vacuum tube or both to measure either dc or ac voltages. Its input impedance is very high, and the current used to actuate the meter movement is not taken from the circuit being measured. It can be used to obtain accurate measurements in sensitive circuits.
VACUUM-TUBE VOLTMETER (VTVM) OR ELECTRONIC
VOLTMETER
the actual measurement of the amount of energy that is being
temporarily stored by circuit capacitance or inductance and is returned to the source during each half cycle.
VAR
VAR
Volt-amperes-reactive. it is sometimes referred to as wattless power.
The voltage between any live conductor of a circuit and earth.
VOLTAGE TO GROUND
WATT
A unit of electric power produced by a current of one ampere at one volt.
? Watts = 1 Horsepower
746 Watts
A unit of electrical work indicating the expenditure of
one watt of electrical power for one hour.
WATTHOUR
Loosely, an electromagnetic impulse, periodically changing in intensity and traveling through space. More specifically the graphical representation of the intensity of that impulse over a period of time.
WAVE
WAVE PROPAGATION
The transmission of RF energy through a medium.
The shape of the wave obtained when instantaneous
values of an ac quantity are plotted against time in rectangular coordinates.
WAVELENGTH
A circuit in which the various values of capacitance and resistance are made to balance with each other at a certain frequency.
WIEN-BRIDGE CIRCUIT
WYE CONNECTION
Also called a star connection. A Y-shaped winding connection.
Used as reference voltage source for larger voltage regulators, and as constant voltage source within large electronic circuits where highly accurate voltage is needed in one or two small areas.
ZENER DIODE

A diode designed such that when reverse biased, the diode acts as a voltage regulator.
The positive electrode such as the plate of a vacuum rube; the element to which the principle stream of electrons flows. This my be an area on the surface of a metal or alloy. (obselete vacuum tube terms)
ANODE
A vacuum-tube circuit which serves simultaneously
as an oscillator and as a heterodyne detector.
(obselete vacuum tube terms)
AUTODYNE CIRCUIT
The electrode in a vacuum tube which is the source of electron emission. Also a negative electrode.
(obselete vacuum tube terms)
CATHODE
The method of biasing a tube by placing the biasing
resistor in the common cathode return circuit, making the cathode more positive, rather than the grid more negative, with respect to ground.
(obselete vacuum tube terms)
CATHODE BIAS
The electrode of a vacuum tube other than a diode upon
which the signal voltage is impressed in order to control the plate current.
(obselete vacuum tube terms)
CONTROL GRID
An electron tube having two electrodes, a cathode and an anode.
(obselete vacuum tube terms)
DIODE
A demodulator in which one or more semiconductor or electron-tube diodes are used to provide a rectified output that has an average value proportional to the original modulation.
(obselete vacuum tube terms)
DIODE DEMODULATOR / DIODE DETECTOR
Current which flows between the cathode and the grid
whenever the grid becomes positive with respect to the cathode.
(obselete vacuum tube terms)
GRID CURRENT
Also called equipotential or
unipotential cathode. A cathode which is heated by an independent heater.
(obselete vacuum tube terms)
INDIRECTLY HEATED CATHODE
A five-electrode vacuum tube containing a cathode, control grid, screen grid, suppressor grid, and plate.
(obselete vacuum tube terms)
PENTODE
The principle electrode in a tube to which the electron stream is attracted.
(obsolete vacuum tube terms)
PLATE (P)
The complete electrical circuit connecting the cathode
and plate of an electron tube.
(obsolete vacuum tube terms)
PLATE CIRCUIT
The current flowing in the plate circuit of an electron tube.
(obsolete vacuum tube terms)
PLATE CURRENT
An electron tube designed to handle a greater amount of
power than the ordinary voltage-amplifying tube.
(obsolete vacuum tube terms)
POWER TUBE
The bias of a tube created by the voltage drop developed across a resistor through which its cathode current flows.
(obsolete vacuum tube terms)
SELF-BIAS
A three-electrode vacuum tube, containing a cathode, control grid, and plate.
(obsolete vacuum tube terms)
TRIODE
A hot-cathode gas tube in which one or more control
electrodes initiate the anode current, but do not limit it except under certain operating conditions.
(obsolete vacuum tube terms)
THYRATRON