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The neutral conductor of a 3-phase, 4-wire system and the middle conductor of a 2- phase, 3-wire system must have at least 2 separate and distinct earth connections with a minimum of 2 different earth electrodes to have a satisfactory earth resistance; The earth electrodes must be interconnected to reduce earth resistance
Distributing single-phase loads among the phases of a three-phase system balances the load and makes most economical use of conductors and transformers. In a symmetrical three-phase four-wire wye system, the three phase conductors have the same voltage to the system neutral.
An older, but still widely used, high-leg delta system uses three phases with 240 volts phase-to-phase for motor loads, and 120 volts for lighting loads by use of a center-tapped transformer; two of the phases are 120 volts to neutral. The third phase, the "high leg" of the system (also referred to as the "wild leg"), has 208 V to neutral and ...
The conductor that connects to the star point in a three-phase system, or that carries the return current in a single-phase system, is called neutral (N). Three variants of TN systems are distinguished: TN−S PE and N are separate conductors that are connected together only near the power source. TN−C
The voltages between the three phases are the same in magnitude, however the voltage magnitudes between a particular phase and the neutral vary. The phase-to-neutral voltage of two of the phases will be half of the phase-to-phase voltage. The remaining phase-to-neutral voltage will be √ 3 /2 the phase-to-phase voltage. So if A–B, B–C and ...
In North America, overhead distribution systems may be three phase, four wire, with a neutral conductor. Rural distribution system may have long runs of one phase conductor and a neutral. [17] In other countries or in extreme rural areas the neutral wire is connected to the ground to use that as a return (single-wire earth return).
In a three-phase system, at least two transducers are required to measure power when there is no neutral, or three transducers when there is a neutral. [5] Blondel's theorem states that the number of measurement elements required is one less than the number of current-carrying conductors. [6]
In Europe, three-phase 230/400 V is most commonly used. However, 130/225 V, three-wire, two-phase electric power discontinued systems called B1 are used to run old installations in small groups of houses when only two of the three-phase high-voltage conductors are used. The phase shift in Europe is 120°, as is the case with three-phase current.