Power Distribution Systems

phase converters

Single-phase power can be obtained from any three-phase electrical system by connecting any two phase leads. However, it is not possible to obtain three-phase power from a single-phase power source without recourse to either a rotary or static phase converter A rotary phase converter is a machine that can convert single-phase power to three phase …

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power factor

If AC current and voltage were always in phase, the average power over a complete cycle would be equal to the product of the current and voltage and power could be measured in watts. However, this is a theoretical situation because there is always some reactance present in an AC circuit that keeps the current …

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what is voltage regulator

All of the components in an electrical system are designed to operate at their rated voltages for optimum efficiency and long service. An ideal electrical system would provide constant voltage to all customers under all conditions of load. Unfortunately, because of the unpredictable dynamics of a practical system, none is ideal. Thus, it is necessary …

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wall switch wiring diagrams

The single-pole, wall-mounted toggle switch, as shown in below Figure , is the most commonly used switch in homes and offices. These wall switch wiring diagrams have the two brass screw terminals on the right side of the switch for the connection of black “hot” wires. It makes no difference which “hot” wire (input or …

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nec branch circuit requirements

The National Electrical Code (NEC 2002) provides guidance for electrical contractors and electricians, but it is really intended for use by governmental agencies that have legal jurisdiction over electrical installations and authorized electrical and insurance inspectors. The many mandatory chapters include Chapter 2, “Wiring and Protection,” Chapter 3, “Wiring Methods and Materials,” and Chapter 4, …

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Electrical Boxes

NEC 2002, Article 314, “Outlet, Device, Pull, and Junction Boxes; Conduit Bodies; Fittings; and Manholes,” requires that wire connections or cable splices be contained inside approved metal or plastic boxes. This provision is intended to shield wood building framing members or other adjacent flammable objects from electrical sparks should the wiring be defective. Boxes also …

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Wire Insulation and Cable Coding

INSULATED WIRE CODING The wire manufacturers’wire markings give: Wire gauge Maximum voltage rating Insulation code (R for thermoset, T for thermoplastic, X for cross-linked polyethylene thermoset) Maximum temperature code (H for 75°C, HH for 90°C, nothing for 60°C) Abbreviation for sheath if present (e.g., N for nylon) The identification codes for wires with thermoplastic insulation …

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gfci circuit breakers

The NEC requires that ground-fault circuit interrupters (GFCI CIRCUIT BREAKERS ) be installed in many different rooms and locations in both public and private buildings. They are now required in bathrooms, kitchens, appliance rooms or spaces, and garages. In addition, they are required in basements, near swimming pools, hot tubs, or fountains, and in outdoor …

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