BU 2: Elecrical Systems (TERMS)

Admittance

reciprocal of impedance

Air blast transformer

a transformer cooled by forced circulation of air though its core and coils.

Air switch

a switch in which the interruption of the circuit occurs in air.

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 to ELECTRICAL POWER.

Ammeter

An instrument for measuring electric current.

Ampacity

CURRENT THAT A CONDUCTOR CAN CARRY CONTINOUSLY under the conditions of use without exceeding its temperature rating.

Ampere

A charge flow of one coulomb per second.

Appliance

CURRENT-CONSUMING EQUIPMENT, fixes or portable, such as heating or motor operated equipment.

Appliance branch circuit

A branch circuit that SUPPLIES ENERGY TO ONE OR MORE OUTLETS to which appliances are connected.

Armored cable

a CABLE provided with a WRAPPING OF METAL, for mechanical protection.

Askarel

a SYNTHETIC NON-FLAMMABLE INSULATING LIQUID which when decomposed by electric arc, evolves only non-flammable gaseous mixture.

Automatic transfer equipment

A device used to TRANSFER LOAD from one pwer source to another. eg. transfer switch, switchboard assembly

Autotransformer

A transformer in which part of the winding is common to both the primary and secondary circuits.

Auxiliary

A device or equipment which AIDS THE MAIN DEVICE or equipment.

Auxiliary Gutter

a SHEET METAL ENCLOSURE for conductors, cables, and bus bars at switchboards.

Ballast

a device used with fluorescent and high intensity discharge lamps to PROVIDE NECESSARY CIRCUIT CONDITION for starting and operating the lamp.

Branch circuit

the circuit conductors between the final overcurrent device protecting the circuit and the outlets.

Branch conductor

a CONDUCTOR THAT BRANCHES OFF at an angle from a continous run of conductor.

Buna

A conductor or group of conductors that SERVES AS A COMMON CONNECTION for three or more circuits in a switchgear assembly.

Busbar

A METALLIC BAR USED TO PROVIDE COMMON CONTACT or termination for a group of all wires or cables.

Cable sheath

The PROTECTIVE COVERING such as non-metallic materials as plastic APPLIED OVER A CABLE.

Circuit breaker

a device DESIGNED TO OPEN AND CLOSE A CIRCUIT by automatic means and to open the circuit automatically on a predetermined over-current.

Circuit homerun

In a wiring diagram, an ARROW HAVING CIRCUIT NUMBER designating the point at which such branch circuit will be connected.

Circular mil

A unit for measuring the CROSS-SECTIONAL AREA of a conductor.

Conductance

a measure of permissiveness to charge flow; reciprocal of resistance.

Bare conductor

a conductor having NO COVERING/INSULATION whatsoever.

Covered conductor

a conductor encased within material of composition that is NOT RECOGNIZED BY CODE as insulation.

Insulated conductor

a conductor encased within material of composition that is RECOGNIZED BY CODE.

Conductivity

a measure of the ability of a material to conduct electric current; reciprocal of resistivity of a substance.

Conduit

a structure containing one or more ducts; commonly formed from iron or other tubing.

Conduit fittings

accessories used to complete a conduit system such as boxes, bushings and access fittings.

Convenience outlet

An outlet which RECEIVES THE PLUG with flexible cord of electrical appliances or equipment.

Copper-clad aluminum conductor

conductors drawn from a copper-clad aluminum rod with the copper metallurgically bonded to the aluminum core.

Coulomb

an electric charge of 6.28 x 10^8 electrons.

Current

the rate of charge flow.

Cutout box

an ENCLOSURE DESIGNED FOR SURFACE MOUNTING that has swinging doors secured directly to and telescoping with the walls of the boc proper.

Demand factor

The RATIO of the MAXIMUM DEMAND SYSTEM to the CONNECTED LOAD of a system.

Device

a unit of an electrical system that is INTENDED TO CARRY but NOT UTILIZE ELECTRIC ENERGY.

Direct current

A UNIDIRECTIONAL CURRENT with a constant value.

Disconnecting means

A device, group of device by which the conductors of a circuit can be disconnected from their source of supply.

Distribution center

A point at which ENERGY IS DIVIDED AMONG FEEDERS OR BRANCH or combination of both and where overcurrent devices are usually located.

Electric circuit

A conducting path which electric charges may flow.

Electric motor

a device for CONVERTING ELECTRICAL > MECHANICAL ENERGY.

Electric system

the entire system of conductors, equipments, and devices.

Electric units

comprise the volt, ampere, ohm, watt, watt-hour, coulomb, henry, farad, joule, etc.

Electric surge

a TRANSIENT WAVE OF CURRENT; potential or power in the electric circuit.

Electricity

a physical entity associated with the atomic structure of matter that occurs in polar forms (positive and negative).

Electromagnetic induction

a PROCESS OF EMF GENERATION induced by movement of magnetic flux which cuts an electric conductor.

Electromotive force (EMF)

An ENERGY-CHARGE RELATION that results in electric pressure, which produces or tends to produce charge flow.

Electrostatics

a branch of electrical science dealing with the LAWS OF ELECTRICITY AT REST.

Emergency light

a TEMPORARY SOURCE OF LIGHT provided by a lamp powered by storage battery within the unit.

Farad

UNIT OF CAPACITANCE defined by the production of one volt across that capacitor terminals when a charge of 1 coulomb is stored.

Feeder

All circuit conductors between the service equipment.

Flashover

DISRUPTIVE ELECTRICAL DISCHARGE around or over an insulator.

Flexible conduit

NON- RIGID CONDUIT into which conductors may be drawn.

Frequency

the NUMBER OF PERIODS occurring in unit time of a periodic process such as in the flow of electric charge.

Fuse

protective device with a fusible element that OPENS THE CIRCUIT by melting WHEN SUBJECTED TO EXCESSIVE CURRENT.

Galvanometer

An instrument for measuring comparatively small currents.

General purpose branch circuit

A branch circuit that supplies a number of outlets for lighting and appliances.

Generator

a machine that CONVERTS MECHANICAL> ELECTRIC ENERGY utilizing electromagnetic induction principle.

AC Generator

also known as ALTERNATOR; produces alternating current.

DC Generator

generator that produces DIRECT CURRENT.

Ground

a conducting connection between an electric circuit/equipment and earth, or to some conducting body that serves in place of the earth.

Grounded circuit

a CIRCUIT in which one conductor or point is intentionally GROUNDED either solidly or through a grounding device.

Grounded conductor

A system or circuit CONDUCTOR that is intentionally GROUNDED.

Ground-Fault Circuit Interrupter (GFCI)

A device installed in circuits where current leakage can be especially dangerous; SHUTS OFF CURRENT FLOW within 0.025 sec at the onset of leak as small as 5 milli-amperes.

Grounding electrode Conductor

The CONDUCTOR used to connect the GROUNDING ELECTRODE to the equipment grounding conductor.

Henry

A unit of inductance.

Hysterisis

the magnetic property of a substance which results from residual magnetism.

Impedance

Opposition to AC current by combination of resistance and reactance; measured in ohms.

Individual branch circuit

a branch circuit that SUPPLIES ONLY ONE UTILIZATION EQUIPMENT.

Insulated

SEPARATED FROM OTHER CONDUCTING SURFACES by dielectric permanently offering high resistance to passage of current and disruptive discharge.

Insulator

a material or substance that DOES NOT ALLOW THE FLOW OF ELECTRICITY through it.

Interrupting rating

the highest current rating at rated voltage that a device is intended to interrupt under standard test conditions.

Inverter

a device used to CONVERT DC TO AC.

Isolating switch

a switch intended for isolating an electric circuit from the power source.

Jumper

a SHORT LENGTH CONDUCTOR used to make a connection between terminals or around a break in a circuit.

Junction box

a BOX with a blank cover that JOINS DIFFERENT RUNS OF RACEWAYS OR CABLE provided with sufficient space for connection and branching of the enclosed conductors.

Kilowatt-hour

A unit energy equal to the energy transferred or expended by ONE KILOWATT IN ONE HOUR.

Knife switch

a switch in which the circuit is closed by moving a blade engaging contact clips.

Lighting outlet

an OUTLET used for direct connection of a LAMPHOLDER, LIGHTING FIXTURE, or a cord that supplies a lampholder.

Lighting arrestor

A device for providing path by which LIGHTNING DISTURBANCES ARE PASSED TO EARTH; intended to prevent damage to electrical apparatus due to lightning.

Damp location

PARTIALLY PROTECTED LOCATIONS under canopies, marquees, roofed open porches, etc.

Dry location

A location not normally subject to dampness/wetness.

Wet location

installations underground or in concrete slabs or masonry in direct contact with earth, and LOCATIONS SUBJECT TO SATURATION WITH WATER.

Maximum demand

Maximum demand of an installation/ system is the largest of all the demands which have occured during the specified period of time.

Metal-clad

a component so constructed that the conducting parts are ENTIRELY ENCLOSED IN METAL CASING/ ENCLOSURE.

Meter center

a point or a place WHERE ALL METERS MAY BE LOCATED.

Moisture-resistant

a device/ equipment/ conductor constructed that exposure to MOIST ATMOSPHERE WILL NOT READILY CAUSE INJURY in its quality.

Mho

unit of CONDUCTANCE; reciprocal of ohm.

Ohm

unit of RESISTANCE.

Ohmmeter

an instrument for measuring resistance values.

Ohm's law

a law stating that current is directly proportional to the applied voltage and inversely proportional to resistance.

Outlet

a point in a wiring system from which current is taken for supply of fixtures, lamps, heaters, etc.

Overcurrent

any CURRENT IN EXCESS OF THE RATED CURRENT of the equipment or the ampacity of the conductor.

Overload

Operation of equipment in EXCESS OF NORMAL, FULL LOAD RATING.

Panelboard

A single group of panel units designed for assembly in the form of a single panel.

Plug

a device inserted into a receptacle for connection of a cord to the conductor terminations in the receptacle.

Potential difference

produced when 1 unit of work is done in separating unit charges through unit distance.