https://wiki.nivel-teorico.com/index.php?action=history&feed=atom&title=Sistema_polif%C3%A1sicoSistema polifásico - Histórico de revisões2026-06-07T05:58:03ZHistórico de edições para esta página nesta wikiMediaWiki 1.40.1https://wiki.nivel-teorico.com/index.php?title=Sistema_polif%C3%A1sico&diff=5057&oldid=prevCalimero0000: uma edição2013-05-02T23:58:25Z<p>uma edição</p>
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O '''sistema polifásico''' é um meio de [[distribuição de energia|distribuição]] de [[energia elétrica]] de [[corrente alternada]].<!-- Sistemas polifásicos empregam três ou mais condutores elétricos energizados Polyphase systems have three or more energized electrical conductors carrying alternating currents with a [[phase (waves)|definite time offset]] between the voltage waves in each conductor. Polyphase systems are particularly useful for transmitting power to electric motors. The most common example is the [[three-phase power]] system used for industrial applications and for power transmission. The most obvious advantage of three-phase power transmission using three wires, as compared to single-phase power transmission over two wires, is that the power transmitted in the three-phase system is the voltage multiplied by the current in each wire times the square root of three (approximately 1.73). The power transmitted by the single-phase system is simply the voltage multiplied by the current. Thus the three-phase system transmits 73% more power but uses only 50% more wire.<br />
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[[Image:3 phase AC waveform.svg|thumb|300px|right|One voltage cycle of a three-phase system]]<br />
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== Phases ==<br />
In the very early days of commercial electric power, some installations used [[Two-phase electric power|two-phase]] four-wire systems for motors. The chief advantage of these was that the winding configuration was the same as for a single-phase capacitor-start motor and, by using a four-wire system, conceptually the phases were independent and easy to analyse with mathematical tools available at the time. Two-phase systems have been replaced with three-phase systems. A two-phase supply with 90 degrees between phases can be derived from a three-phase system using a [[Scott-T transformer|Scott-connected transformer]].<br />
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A polyphase system must provide a defined direction of phase rotation, so mirror image voltages do not count towards the phase order. A 3-wire system with two phase conductors 180 degrees apart is still only single phase. Such systems are sometimes described as [[Split-phase electric power|split-phase]].<br />
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== Motors ==<br />
Polyphase power is particularly useful in [[Alternating current|AC]] motors, such as the [[induction motor]], where it generates a rotating [[magnetic field]]. When a three-phase supply completes one full cycle, the magnetic field of a two-pole motor has rotated through 360° in physical space; motors with more pairs of poles require more power supply cycles to complete one physical revolution of the magnetic field and so these motors run slower. [[Nikola Tesla]] and [[Michail Dolivo-Dobrovolsky]] invented the first practical induction motors using a rotating magnetic field - previously all commercial motors were DC, with expensive [[commutator (electric)|commutators]], high-maintenance brushes and characteristics unsuitable for operation on an alternating current network. Polyphase motors are simple to construct, are self-starting and have little vibration compared with single-phase motors.<br />
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== Higher phase order ==<br />
Higher phase numbers than three have been used. A common practice for [[rectifier]] installations and in [[HVDC]] converters is to provide six phases, with 60 degree phase spacing, to reduce harmonic generation in the AC supply system and to provide smoother direct current. Experimental high-phase-order transmission lines have been built with up to 12 phases. These allow application of [[Extra high tension|Extra High Voltage (EHV)]] design rules at lower voltages and would permit increased power transfer in the same transmission line corridor width.<br />
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== {{Ver também}} ==<br />
* [[Componentes simétricos]]<br />
* [[Corrente alternada]]<br />
<!--* [[Conversor de fase]]<br />
* [[Polyphase coil]]--><br />
* [[Charles Proteus Steinmetz]]<br />
<!--* [[John Hopkinson]]--><br />
* [[Motor elétrico]]<br />
<!--* [[Transformador Y-Δ]]--><br />
* [[Nikola Tesla]]<br />
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== Leitura posterior ==<br />
* Thompson, S. P. (1900). [http://books.google.com/books?id=TvwHAAAAMAAJ Correntes polifásicas e motores de corrente alternada]. New York: Spon & Chamberlain.<br />
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{{DEFAULTSORT:Sistema Polifasico}}<br />
[[Categoria:Eletricidade]]<br />
[[Categoria:Nikola Tesla]]</div>Calimero0000