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The Book of Terms

The Book of TermsThe WJI Book of Wire & Cable Terms: an interactive experience of learning and sharing
This book, written by industry volunteers and containing more than 5,000 entries, is an asset for newcomers to wire and cable.

At the same time, it also represents an opportunity for industry veterans to give back by either updating or adding to the more than 5,000 entries. This is an honor system process. Entries/updates must be non-commercial, and any deemed not to be so will be removed. Share your expertise as part of this legacy project to help those who will follow. Purchase a printed copy here.

   

 

All   0-9   A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

Thermoelectricity

When two dissimilar metals are bonded together and heated, a voltage can be produced. Such a bond is called a thermocouple. Electricity generated by heat action is thermoelectricity.

Thermoembrittlement

A term for the condition of some insulating materials that have become embrittled and cracked after being subjected to elevated temperatures while under stress.

Thermoplastic

A material that can be softened repeatedly by heating and hardened by cooling through a temperature range characteristic of the plastic. In the softened state, it can be shaped by molding or extrusion. In its cooled state it retains the shape imparted when hot. It is the opposite of a thermoset material.

Thermoplastic Elastomer

A jacket material that has many of the characteristics of rubber, as well as excellent electrical, mechanical and chemical properties. A thermoplastic material, it is less expensive than neoprene or chlorosulfonated polyethylene.

Thermoset

A classification of resin used for insulation that is crosslinked by a heating process known as curing. Once the plastic is cured, it cannot be re-softened or distorted from its formed shape. It is the opposite of a thermoplastic material.

Thermostat

A temperature-sensitive device that automatically opens and closes an electric circuit to regulate the temperature of the space with which it is associated.

Thermostat Wire

Single or multi-conductor wire, bare soft solid copper conductor, usually PVC-insulated. May be twisted and/or jacketed. May have enameled or nylon covered conductors and may have a metal armor covering.

THHN

Designation for thermoplastic insulated, high heat resistant, nylon jacketed building cable, 90°C (194°F), 600 volt, dry and damp locations.

THHN-2

Designation for cable similar to THHN, but with a 90°C (194°F) wet rating.

Thimble

A grooved metal fitting to protect the eye of a wire rope.

Thomson Effect

The absorption or evolution of thermal energy produced by the interaction of an electric current and a temperature gradient in a homogeneous electric conductor.

Thread Rolling

A cold working process in which a thread form is impres­sed on the work piece by rolling it between hardened steel dies. The grain of the material is not cut as in thread cutting, but regrouped by plastic deformation into the shape of the thread profile. Advantages associated with thread rolling include cons­tant sizing, burnishing, surface hardening, wear and corrosion resistance, greater tensile strength, greater resistance to bending and significantly improved fatigue life.

Threading-up

The process of threading a wire through a wiredrawing machine. Also known as “stringing” a machine.

Three-Conductor Cable

Three insulated conductors assembled with other necessary cable components such as shield and filler to form a core, protected by an overall jacket.

Three-High Mill

A stand that has three rolls, one above the other. The material that is being rolled passes one way between the bottom and middle rolls, and the other way between the middle and top rolls. The rolls are driven so that the top and bottom rolls revolve clockwise while the center roll turns counterclockwise. Thus a piece fed between the top and center rolls may be returned through the center and bottom rolls.

Three-Phase Circuit

A polyphase circuit of three interrelated voltages for which the phase difference is 120°. The common form of generated power, three-phase current is delivered through three wires, with each wire serving as a return for the other two and with three current components differing in phase successively by one-third cycle or 120 electrical degrees. A four-wire system, which includes a ground, is sometimes used in local installations.

Three-Quarters Hard

A temper of nonferrous alloys characterized by values of tensile strength and hardness about three-quarters of the way between dead soft and full hard.

Three-Way Switch

A switch used in pairs to control one piece of electrical equipment from two different points.

Three-Wire System

A DC or single-phase AC system comprising three conductors, one of which (the neutral wire) is maintained at a potential midway between the potential of the other two.

Thumper

1) A device used to locate faults in a cable by the release of power surges from a capacitor, characterized by the audible noise when the cable breaks down. 2) The mechanism within a cable-packaging machine that shakes the container by raising and rapidly dropping the container a short distance. Used to settle the cable within the pack, enabling more cable to fit into the container.
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