What Every Purchaser Needs to Know About Sourcing Wire & Cable: Your Guide to Wire & Cable Procurement

Types of Conductors, Insulation & Jackets

Even when selecting a simple single, insulated wire many factors must be considered: temperature rating, voltage, DC resistance of the conductor, insulation, outer diameter (often shortened to O.D.), required flexibility, physical properties of the conductor (tensile strength, voltage drop, conductivity, weight) and when necessary, specific electrical characteristics such as the dielectric properties of the insulating material.


Before selecting a particular insulated conductor, numerous factors should be considered. Those that pertain to the conductor are: size, stranding and material.


Conductor Size

SIZE: Determined with regard to DC resistance, current carrying capacity and breaking strength requirements.


GAUGE: The most important consideration in calculating the individual wire gauge size is the circular mil area minimum as called out by the American Society for Testing Materials (ASTM) to meet UL, CSA and military requirements, and by the Society of Automotive Engineers (SAE) for most automotive products.


Gauge is expressed as American wire gauge (AWG) in North America. As gauge number increases, the diameter of wire decreases.

So now that you understand the anatomy of wire and cable, we can get into how to choose the right kind of each for your needs. The key is selecting the correct compound for each individual component part of your cable.

Conductors

Ampacity Values

Ampacity, or current carrying capacity, is defined as the current a conductor can carry before its temperature rise exceeds a permissible value. The correct conductor size ensures that the heat generated by the flow of current through the conductor and the heat of the ambient temperature does not exceed the thermal rating of the insulation.


There are many factors which will limit the amount of current that can be passed through a wire:


CONDUCTOR SIZE: The larger the circular mil area, the greater the current capacity.


INSULATION: The amount of heat generated should never exceed the maximum temperature rating of the insulation.


CONDUCTOR NUMBER: Heat dissipation is lessened as the number of individually insulated conductors that are bundled together are increased.


INSTALLATION CONDITIONS: Restricting heat dissipation by installing the conductors in conduit, duct, trays or raceways lessens the current carrying capacity. This restriction can be alleviated by using proper ventilation methods, forced air cooling, etc.

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Insulation

One of the most important parts of a wire is its insulation. The selection of insulation is determined by a number of factors including stability and required life, dielectric properties, resistance to temperature, resistance to moisture, mechanical strength and flexibility. There is no single insulation that is ideal in every one of these applications. It is necessary to select a product with the type of insulation which best meets the requirements of the application. For example, compressor motors used in refrigerators must use wire insulations which are compatible with the refrigerants to which the wire will be exposed. The refrigerator box must be wired with material that will not impart odors to food, etc. Similarly, gasoline pumps need wire that will not deteriorate in the presence of gasoline vapors. There are also applications where the wire must be able to withstand exposure to liquids or chemicals. 


There are many requirements in high-production applications where the process dictates the kind of insulation chosen. Insulation must be solder-resistant in some electronic applications where circuit boards are used. Other applications call for wire capable of encapsulation or that will withstand varnish treatment and bake cycles.

Jackets

While most extruded types of insulation are also used as jackets, there are some compounds and combinations of compounds used exclusively for jacketing. Often a combination of compounds will be sandwiched together to form a jacket.

What Every Purchaser Needs to Know About Sourcing Wire & Cable

Download the entire e-book in one convenient PDF.

Your information will be used to send you the presentation and subscribe you to the IEWC Network. You may unsubscribe at any time.

IEWC is committed to protecting your personal information and will not share your information with third parties. For more information, please see our Privacy Policy.

Your Guide to Wire & Cable Procurement

Download the entire e-book:

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