**100 amp Wire**

**Electricity**

Electricity, simply put, is the flow of electric current along a conductor. This electric current takes the form of free electrons that transfer from one atom to the next. Thus, the more free electrons a material has, the better it conducts. There are three primary electrical parameters: the volt, the ampere and the ohm.

**Volt**

The pressure that is put on free electrons that c`Preformatted text`

auses them to flow is known as electromotive force (EMF). The volt is the unit of pressure, i.e., the volt is the amount of electromotive force required to push a current of one ampere through a conductor with a resistance of one ohm.

**Ampere**

The ampere defines the flow rate of electric current. For instance, when one coulomb (or 6 x 1018 electrons) flows past a given point on a conductor in one second, it is defined as a current of one ampere.

**Ohm**

The ohm is the unit of resistance in a conductor. Three things determine the amount of resistance in a conductor: its size, its material, e.g., copper or aluminum, and its temperature. A conductor’s resistance increases as its length increases or diameter decreases. The more conductive the materials used, the lower the conductor resistance becomes. Conversely, a rise in temperature will generally increase resistance in a conductor.

## Summary

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**[Ohm’s Law**

Ohm’s Law defines the correlation between electric current (I), voltage (V), and resistance (R) in a conductor. Ohm’s Law can be expressed as: V = I × R Where: V = volts I = amps R = ohms

**Ampacity**

Ampacity is the amount of current a conductor can handle before its temperature exceeds accepted limits. These limits are given in the National Electrical Code (NEC), the Canadian Electrical Code and in other engineering documents such as those published by the Insulated Cable Engineers Association (ICEA). It is important to know that many external factors affect the ampacity of an electrical conductor and these factors should be taken into consideration before selecting the conductor size.

**Conductors**

The conductor is the metallic component of cables through which electrical power or electrical signals are transmitted. Conductor size is usually specified by American Wire Gauge (AWG), circular mil area or in square millimeters.

**AWG**

AWG The American Wire Gauge (sometimes called Brown and Sharpe or B. and S.) is used almost exclusively in the USA for copper and aluminum wire. The Birmingham Wire Gauge (BWG) is used for steel armor wire. The diameters according to the AWG are defined as follows: The diameter of size 4/0 (sometimes written 0000) equals 0.4600 inch and that of size #36 equals 0.0050 inch; the intermediate sizes are found by geometric progression. That is, the ratio of the diameter of one size to that of the next smaller size (larger gauge number) is: √ _4 = 1.122932 _____ 0.4600 0.0050 39

**Circular Mil**

Sizes larger than 4/0 are specified in terms of the total area of a cross-section of the copper in circular mils (cmil). A circular mil is a unit of area equal to the area of a circle one mil in diameter. It is p/4 (equal to 0.7854) of a square mil (one mil=0.001 inch). The area of a circle in circular mils is therefore equal to the square of its diameter in mils. A solid wire one inch in diameter has an area of 1,000,000 cmils, whereas one square inch equals 4/p x 1,000,000 cmils (equal to 1,273,200 cmils).

**Square Millimeters**

Metric sizes are given in terms of square millimeters (mm2 ).

**Conductor Characteristics**

Relative electrical and thermal conductivities of common metal conductors are as follows:

metal | Relative Electrical Conductivity at 20℃ | Relative Thermal Conductivity at 20℃ |
---|---|---|

Silver | 106 | 108 |

Copper ( Annealed) | 100 | 100 |

Copper (Hard Drawn ) | 97 | – |

Gold | 72 | 76 |

Aluminum | 62 | 56 |

Magnesium | 39 | 41 |

Zinc | 29 | 29 |

Nickel | 25 | 15 |

Cadmium | 23 | 24 |

Cobalt | 18 | 17 |

Iron | 17 | 17 |

Platinum | 16 | 18 |

Tin | 15 | 17 |

Steel | 12 | 13-17 |

Lead | 8 | 9 |

**Concentric Strand**

A concentric stranded conductor consists of a central wire or core surrounded by one or more layers of helically laid wires. Each layer after the first has six more wires than the preceding layer. Except in compact stranding, each layer is usually applied in a direction opposite to that of the layer under it. If the core is a single wire and if it and all of the outer strands have the same diameter, the first layer will contain six wires; the second, twelve; the third, eighteen; etc.

**Bunch Strand**

The term bunch stranding is applied to a collection of strands twisted together in the same direction without regard to the geometric arrangement.

**Rope Strand**

A rope stranded conductor is a concentric stranded conductor each of whose component strands is itself stranded. A rope stranded conductor is described by giving the number of groups laid together to form the rope and the number of wires in each group.

**Sector Conductor**

A sector conductor is a stranded conductor whose cross-section is approximately the shape of a sector of a circle. A multiple conductor insulated cable with sector conductors has a smaller diameter than the corresponding cable with round conductors.

**Segmental**

Conductor A segmental conductor is a round, stranded conductor composed of three or four sectors slightly insulated from one another. This construction has the advantage of lower AC resistance due to increased surface area and skin effect.

**Annular Conductor**

An annular conductor is a round, stranded conductor whose strands are laid around a suitable core. The core is usually made wholly or mostly of nonconducting material. This construction has the advantage of lower total AC resistance for a given cross-sectional area of conducting material due to the skin effect.

**Compact Strand**

A compact stranded conductor is a round or sector conductor having all layers stranded in the same direction and rolled to a predetermined ideal shape. The finished conductor is smooth on the surface and contains practically no interstices or air spaces. This results in a smaller diameter

**Compressed Strand**

Compressed conductors are intermediate in size between standard concentric conductors and compact conductors. A comparison is shown below: Solid Compact Compressed Concentric Figure 2.8–Comparative Sizes and Shapes of 1,000 kcmil Conductors In a concentric stranded conductor, each individual wire is round and considerable space exists between wires. In a compressed conductor, the conductor has been put through a die that “squeezes out” some of the space between wires. In a compact conductor each wire is preformed into a trapezoidal shape before the wires are stranded together into a finished conductor. This results in even less space between wires. A compact conductor is, therefore, the smallest in diameter (except for a solid conductor, of course).