Module 2: Electrical Conductor and Insulators

electrical conductors

• substances with high conductivity, which have very mobile electrons

• ex.: copper, silver, gold

bare conductor

a conductor having no covering or insulation

covered conductor

encased within a material of composition and thickness not recognized by code

insulated conductor

• encased within a material composition and thickness recognized by code

• examples:

  • silver

  • copper

  • zinc

  • aluminum

  • nickel

  • brass

  • platinum

  • iron

  • tin

  • lead

Insulation Class A

consists of:

• cotton, silk, paper, and materials of paper composition impregnated or immersed in an insulating

• molded/laminated materials with cellulose filler, phenolic resin, or similar resins

• films/sheets of cellulose acetate or similar cellulose products

• varnishes or enamel applied to conductors

Insulation Class B

• consists of mica, asbestos, or fiberglass

• all with a binder

Insulation Class C

consists entirely of mica, porcelain, glass, quartz, or similar materials

Insulation Class O

• consists of cotton, silk, paper, or similar materials that are not impregnated or immersed in an insulating liquid

• examples:

  • rubber

  • porcelain

  • varnish

  • slate

  • glass

  • mica

  • latex

  • asbestos

  • thermoplastic

  • oil wax

  • dry air

  • paper

  • silk

  • wood

Wires

• electrical conductors which are 8 mm² (No. 8 AWG) or smaller

• cables are larger than this

• types:

  • solid

  • stranded

• single conductor number 14 AWG, 12 AWG, 10 AWG, and 8 AWG

Cable

• larger than wires

• electrical conductors larger than wires

• a single number 6 AWG to 0000 AWG

• 2 or more wires assembled in a single jacket

• conductors with sizes from Number 6 AWG and larger are stranded

AWG (American Wire Gauge)

• also known as Brown and Sharpe (B & S) Wire Gauge, is a U.S. standard set of non-ferrous wire conductor sizes

• The gauge means the diameter

  • The higher the gauge number, the smaller the diameter and the thinner the wire

    • Since thicker wire carries more current because it has less electrical resistance over a given length, thicker wire is better for longer distances

• preceded by a number which indicates the size of the wire, e.g. 14

• used in reverse order

  • the bigger the number, the smaller the size

    • smaller sizes: 16, 18, 20, 22, etc.- not permitted to be used in electrical circuits

• MCM (Thousand Circular Mil), M being the Roman numeral for thousand

Solid Wire/ Solid-core / Single-strand wire

• consists of one piece of wire on its entire section

• has flexibility that stranded wire

stranded wire

• consists of a group of wires twisted to form metallic string

• the total circular mil area is found by multiplying the circular mil area of each strand by the total number of strands

cord

refers to insulated wire that is flexible

Bus, Busbar

• a rigid electric conductor, usually a metal bar, hollow tube, or rod

• forms a connection between electric circuits

Copper

• conductor

• properties:

  • ductile

  • malleable

  • excellent conductor of heat and energy

• harder than zinc

• softer than iron

• approximately 50% of its total output is used for manufacturing electrical apparatuses and conductors

Aluminum

• conductor

• produced by the formation of many of many metals, such as feldspar, mica, alum, cryolite, clay, bauxite, and several forms of ________

Circular Mil (CM)

• unit of measuring cross-section size in AWG

• ____ means 1/1000 of an inch (0.001 in.)

• area of circular wire having a diameter of a

• to o find the number of _______ in a circle of a given diameter, square the number of ____ in the diameter

Square Mil

• the area of a square having its side equal to 1 ___