|
A polyphase system is a means of distributing alternating current electrical power. The most common example are three-phase power systems used in industrial applications. Electricity distribution is the penultimate process in the delivery of electric power, the part between transmission and user purchase from an electricity retailer. ...
City lights viewed in a motion blurred exposure. ...
Transmission lines in Lund, Sweden Electric power, often known as power or electricity, involves the production and delivery of electrical energy in sufficient quantities to operate domestic appliances, office equipment, industrial machinery and provide sufficient energy for both domestic and commercial lighting, heating, cooking and industrial processes. ...
Three-phase power transformer which is the sole transferpoint for electricity to a suburban shopping mall in Canada. ...
Phases
Main articles: Phase and Phase shifting Phase is an overloaded word used for: instantaneous phase: the current position in the cycle of something that changes cyclically phase shift: a constant difference/offset between two instantaneous phases, particularly when one is a standard reference Waves are amplitudes that change cyclically, often modeled as sinusoidal functions of time...
Definition of phase shift Phase shifting describes relative phase shift in superposing waves. ...
Polyphase systems have two or more overlapping phases. The voltage on each phase is a sine wave, with a fixed time offset, or phase shift, between the phases. Modern utility power generation and distribution is almost universally three phase, with the phases separated by 120° or one third of an AC cycle. It is commonly used in industry, as it is ideally suited to powering the 3-phase induction motor. Phase is an overloaded word used for: instantaneous phase: the current position in the cycle of something that changes cyclically phase shift: a constant difference/offset between two instantaneous phases, particularly when one is a standard reference Waves are amplitudes that change cyclically, often modeled as sinusoidal functions of time...
In trigonometry, an ideal sine wave is a waveform whose graph is identical to the generalized sine function y = Asin[ω(x − α)] + C, where A is the amplitude, ω is the angular frequency (2π/P where P is the wavelength), α is the phase shift, and C is the...
Waves with the same phase Waves with different phases The phase of a wave relates the position of a feature, typically a peak or a trough of the waveform, to that same feature in another part of the waveform (or, which amounts to the same, on a second waveform). ...
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. A split phase electricity distribution system is a 3-wire single-phase distribution system, commonly used in North America for single-family residential and light commercial (up to about 100 kVA) applications. ...
A few older installations in the U.S. used true 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. Most of these have been upgraded to three-phase systems. A two-phase supply with 90 degrees between phases can be derived from a three-phase system using transformers. Two-phase electrical power was used in some early 20th century factories and the distribution systems that served them. ...
Motors Polyphase power is particularly useful in 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 more slowly. Nikola Tesla invented the first practical induction motors using a rotating magnetic field - previously all commercial motors were DC, with expensive commutators, high-maintenance brushes, and characteristics unsuitable for operation on an alternating current network. Polyphase motors are simple to construct, and are self-starting. City lights viewed in a motion blurred exposure. ...
Electric motors of various sizes. ...
Current flowing through a wire produces a magnetic field (B, labeled M here) around the wire. ...
This article or section is in need of attention from an expert on the subject. ...
Conventional continuous current flows from the battery. ...
Higher phase order Higher phase numbers than 3 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 EHV-style design rules at lower voltages, and would permit increased power transfer in the same transmission line corridor width. AC, half-wave and full wave rectified signals A rectifier is an electrical device, comprising one or more semiconductive devices (such as diodes) or vacuum tubes arranged for converting alternating current to direct current. ...
HVDC or high-voltage, direct current electric power transmission systems contrast with the more common alternating-current systems as a means for the bulk transmission of electrical power. ...
Single phase loads on a polyphase system Residences and small businesses are usually supplied with a single phase taken from one of the three utility phases. Individual customers are distributed among the three phases to balance the loads. The generation of AC electric power is commonly three phase, in which the waveforms of three supply conductors are offset from one another by 120°. These three conductors are commonly housed in a single conduit (e. ...
Many larger apartment buildings are fed with 3-phase transformers, with two of the three phases fed to each unit. The phase offset between the two hot wires is therefore only 120 degrees, so that while the voltage from each "hot" wire to neutral is 120V, the voltage between hot wires is only 208V. Some appliances rated for 240V will run satisfactorily on 208V, although heating equipment will only output 75% of its 240 V rating. Special autotransformers can boost 208V to 240V if necessary. This article or section does not cite its references or sources. ...
Running Polyphase Equipment on Single Phase Sometimes it is necessary to run polyphase equipment, most often 3 phase loads, on single phase power. This occurs in rural areas and in cities. When the utility company will not redily supply the needed 3 phase power, or if the cost is prohibitively high, a phase converter is often used. The US Phase Converter Standards Organization is US based non-profit organization which helps keep the standards and ratings for single to 3 phase converters and other similar technology and can prove to be valuable resource. 3 phase loads refers to the various motors, machinery, and equipment that need 3 phase electrical power to run. ...
The US Phase Converter Standards Organization (USPTSO) is the non-profit organization which sets the quality standards for single to 3 phase converters manufactured and sold in the USA. This organization helps guide manufacturers to produce quality products and offer clear and acurate documentation on the phase converter use and...
See also |
Feeds |
Contact