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Three-phase power supply system - a special case of multi-phase electrical circuits, AC systems, which operate by a common source of sinusoidal EMF of the same frequency shifted relative to each other in time to a specific phase angle. In a three-phase system, this angle is 2π / 3 (120 °).
Three-phase alternating current system invented by Nikola Tesla. A significant contribution to the development of three-phase systems introduced MO Dolivo-Dobrovolsky, who first proposed the three- and four-wire AC transmission system
Each of the existing EMF is in its phase of a batch process. Also, the "phase" - it supports these EMF. In three-phase systems, the phase angle is 120 degrees. The phase conductors are indicated in Russian in Latin letters L with a digital index 1 ... 3, or A, B and C
Advantages of three-phase power supply system:
. • Efficiency of power transmission over long distances
. • Less material consumption of 3-phase transformers
• Lower consumption of materials of power cables, as at the same power consumption is reduced currents in phases.
• balanced system.
• The ability to easily obtain a circular rotating magnetic field required for the operation of the electric motor and other electrical devices.
• The possibility of obtaining a single installation of two operating voltages - phase and line, and two levels power when connected to a "star" or "triangle".
• The possibility of a sharp decrease flicker and stroboscopic lamps effect on fluorescent lamps
Due to these advantages, three-phase systems are most common in modern electric power.
The star - is such a compound, when the ends of the generator winding phase (G) connect to a single point, called the neutral point, or neutral. The ends of the phase windings of the consumer (M) is also connected to a common point.
The conductors belonging to different phases are marked by different colors. Different colors also mark the neutral and protective conductors. This is to ensure proper protection against electric shock, as well as ease of maintenance, installation and repair of electrical installations and electrical equipment. In different countries, marking of conductors has its differences.
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