Electrical Engineering Terms R

Rebar. A contraction of the term reinforcement bars, which are half-inch wrought-iron rods suspended in poured concrete to give it added strength. Rated Load. The torque value of the connected load that occurs when the horsepower requirements of the driven load equate to the horsepower rating of the motor and …

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Electrical Engineering Terms S

Sealtight. The trade name for liquid-tight flexible metallic conduit. Semiconductor. A name was given to a group of materials or to compounds of these materials that are neither good insulators nor good conductors of electricity. Because of their four valence electrons (free electrons in the outer shell of the atom), …

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Electrical Engineering Terms T

Timer A relay that will delay the switching of the contacts by a predetermined time. Totally Enclosed Fan Cooled (TEFC). Normally abbreviated to the acronym TEFC, this term describes motor enclosures with the end bells and the cylindrical motor housing sealed to prevent the entrance of moisture or dirt. Often …

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Electrical Engineering Terms U

Ufer ground. Name after the man who invented and tested it, a Ufer ground is a grounding electrode consisting of at least 20 feet (6 m) of 1/2-inch (13 mm) rebar (either a continuous single bar or shorter lengths tied-wired together) or of at least 20 feet of wire-size 4 …

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Electrical Engineering Terms V

Variable Frequency Drive A technology where the rotational speed of an electric motor is controlled or varied electronically. Varying Duty. If an electric motor is nameplate-rated with this type of duty cycle, it is rated to operate at loads, and for intervals of time, both of which may be subject …

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Electrical Engineering Terms W

Wire-Wound Rotor (Wound-Rotor Motor or just Wound Rotor). As compared to a squirrel-cage rotor of an electric motor in which aluminum is cast over a steel rotor frame in a mold, the armature circuit of this rotor consists of preformed wraps of insulated wire (windings) similar to the field windings …

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Purpose of Grounding the Utility Power Distribution

fig 1 The static ground wire in the 3-phase electrical utility power transmission-distribution grid

The transfer of electrical power within the electrical-utility power transmission/distribution grid is normally at high voltage (high tension) to reduce the transmission losses (line losses) along the miles of cable that must be installed between the generating plants and the many cities, commercial and industrial sites, and suburban, as well …

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Reversing Three Phase Induction Motors

Reversing Three Phase Induction Motors

Three phase induction Motor rotation can be reversed by changing any two of the three lines feeding power to the motor. It is common standard practice to switch line 1 and line 3. When the motor needs to be run in a clockwise and a counterclockwise rotation, a reverse starter …

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