Electrical Engineering Terms K

Kirchhoff’s Current Law.   The sum of the currents entering and leaving a node is equal to zero; the sum of the currents entering a node is equal to the sum of the currents leaving that node. Kirchhoff’s Voltage Law.   The sum of the voltage drops in a closed loop …

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Electrical Engineering Terms L

Linear Load. A utilization-equipment load where the wave shape of the current follows — is in phase with — the wave shape of the applied voltage. At the point of common-return on the neutral conductor, linear single-phase AC currents cancel only the unbalanced load current. Line Disturbances. These are fluctuations …

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Electrical Engineering Terms M

Megger. An electrical test instrument that uses a high-voltage output for insulation testing and high-resistance measurements. Motor Starter A device used to supply full line voltage to a motor and include overcurrent protection. Motor Nameplate Every electric motor is labeled with a motor nameplate. The motor nameplate contains information about …

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Electrical Engineering Terms N

NEMA National Electrical Manufacturers Association is a group who publishes electrical and medical imaging standards.   No-Load Condition. An electric motor operating at rated frequency (AC) and rated voltage with the drive train of its mechanical load disconnected from the rotor driveshaft. The motor turns at near synchronous speed, which …

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Electrical Engineering Terms O

Ohmmeter. An electrical test instrument used for lower-value (as compared to high-resistance) electrical resistance measurements. Ohmic Resistance. In defining this resistance: A DC circuit is said to have a resistance of one ohm when one volt will produce a current of one ampere through it. Overcurrent protection A device used …

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Electrical Engineering Terms P

Power Supply A transformer and rectifier circuit are encased together to supply a lower control voltage. Programmable Logic Controllers An industrial computer that is used to control and execute real-world functions based on the programmed logic. Power Supply Provides power to the PLC and converts the incoming powers to various …

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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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