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Three-phase
Three-phase electric power (abbreviated 3φ) is a common type of alternating current used in electricity generation, Electric power transmission, transmission, and Electric power distribution, distribution. It is a type of polyphase system employing three wires (or four including an optional neutral return wire) and is the most common method used by electrical grids worldwide to transfer power. Three-phase electrical power was developed in the 1880s by multiple people. Three-phase power works by the voltage and currents being 120 degrees phase shift, out of phase on the three wires. As an AC system it allows the voltages to be easily stepped up using transformers to high voltage for transmission, and back down for distribution, giving high efficiency. A three-wire three-phase circuit is usually more economical than an equivalent two-wire Single-phase electric power, single-phase circuit at the same line to ground voltage because it uses less conductor material to transmit a giv ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electric Power Transmission
Electric power transmission is the bulk movement of electrical energy from a generating site, such as a power plant, to an electrical substation. The interconnected lines that facilitate this movement form a ''transmission network''. This is distinct from the local wiring between high-voltage substations and customers, which is typically referred to as electric power distribution. The combined transmission and distribution network is part of electricity delivery, known as the electrical grid. Efficient long-distance transmission of electric power requires high voltages. This reduces the losses produced by strong currents. Transmission lines use either alternating current (HVAC) or direct current (HVDC). The voltage level is changed with transformers. The voltage is stepped up for transmission, then reduced for local distribution. A wide area synchronous grid, known as an "interconnection" in North America, directly connects generators delivering AC power with the same rela ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electric Power Distribution
Electric power distribution is the final stage in the delivery of electric power; it carries electricity from the transmission system to individual consumers. Distribution substations connect to the transmission system and lower the transmission voltage to medium voltage ranging between and with the use of transformers. ''Primary'' distribution lines carry this medium voltage power to distribution transformers located near the customer's premises. Distribution transformers again lower the voltage to the utilization voltage used by lighting, industrial equipment and household appliances. Often several customers are supplied from one transformer through ''secondary'' distribution lines. Commercial and residential customers are connected to the secondary distribution lines through service drops. Customers demanding a much larger amount of power may be connected directly to the primary distribution level or the subtransmission level. The transition from transmission to distribu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polyphase System
A polyphase system is a means of distributing alternating-current (AC) electrical power where the power transfer is constant during each electrical cycle. AC phase refers to the phase offset value (in degrees) between AC in multiple conducting wires; ''phases'' may also refer to the corresponding terminals and conductors, as in color codes. Polyphase systems have three or more energized electrical conductors carrying alternating currents with a defined phase between the voltage waves in each conductor; for three-phase voltage, the phase angle is 120° or 2π/3 radians (although early systems used 4 wire two-phase). Polyphase systems are particularly useful for transmitting power to electric motors which rely on alternating current to rotate. The most common example is the three-phase power system used for industrial applications and for power transmission. Compared to a single-phase, two-wire system, a three-phase three-wire system transmits three times as much power for the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alternating Current
Alternating current (AC) is an electric current which periodically reverses direction and changes its magnitude continuously with time in contrast to direct current (DC) which flows only in one direction. Alternating current is the form in which electric power is delivered to businesses and residences, and it is the form of electrical energy that consumers typically use when they plug kitchen appliances, televisions, fans and electric lamps into a wall socket. A common source of DC power is a battery cell in a flashlight. The abbreviations ''AC'' and ''DC'' are often used to mean simply ''alternating'' and ''direct'', as when they modify ''current'' or ''voltage''. The usual waveform of alternating current in most electric power circuits is a sine wave, whose positive half-period corresponds with positive direction of the current and vice versa. In certain applications, like guitar amplifiers, different waveforms are used, such as triangular waves or square waves. Audio a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Transformer
A transformer is a passive component that transfers electrical energy from one electrical circuit to another circuit, or multiple circuits. A varying current in any coil of the transformer produces a varying magnetic flux in the transformer's core, which induces a varying electromotive force (EMF) across any other coils wound around the same core. Electrical energy can be transferred between separate coils without a metallic (conductive) connection between the two circuits. Faraday's law of induction, discovered in 1831, describes the induced voltage effect in any coil due to a changing magnetic flux encircled by the coil. Transformers are used to change AC voltage levels, such transformers being termed step-up or step-down type to increase or decrease voltage level, respectively. Transformers can also be used to provide galvanic isolation between circuits as well as to couple stages of signal-processing circuits. Since the invention of the first constant-potential transfo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Induction Motor
An induction motor or asynchronous motor is an AC electric motor in which the electric current in the rotor needed to produce torque is obtained by electromagnetic induction from the magnetic field of the stator winding. An induction motor can therefore be made without electrical connections to the rotor. An induction motor's rotor can be either wound type or squirrel-cage type. Three-phase squirrel-cage induction motors are widely used as industrial drives because they are self-starting, reliable and economical. Single-phase induction motors are used extensively for smaller loads, such as household appliances like fans. Although traditionally used in fixed-speed service, induction motors are increasingly being used with variable-frequency drives (VFD) in variable-speed service. VFDs offer especially important energy savings opportunities for existing and prospective induction motors in variable-torque centrifugal fan, pump and compressor load applications. Squirrel ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electrical Grid
An electrical grid is an interconnected network for electricity delivery from producers to consumers. Electrical grids vary in size and can cover whole countries or continents. It consists of:Kaplan, S. M. (2009). Smart Grid. Electrical Power Transmission: Background and Policy Issues. The Capital.Net, Government Series. Pp. 1-42. * power stations: often located near energy and away from heavily populated areas * electrical substations to step voltage up or down * electric power transmission to carry power long distances * electric power distribution to individual customers, where voltage is stepped down again to the required service voltage(s). Grids are nearly always synchronous, meaning all distribution areas operate with three phase alternating current (AC) frequencies synchronized (so that voltage swings occur at almost the same time). This allows transmission of AC power throughout the area, connecting a large number of electricity generators and consumers and potenti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
John Hopkinson
John Hopkinson, FRS, (27 July 1849 – 27 August 1898) was a British physicist, electrical engineer, Fellow of the Royal Society and President of the IEE (now the IET) twice in 1890 and 1896. He invented the three-wire (three-phase) system for the distribution of electrical power, for which he was granted a patent in 1882. He also worked in many areas of electromagnetism and electrostatics, and in 1890 was appointed professor of electrical engineering at King's College London, where he was also director of the Siemens Laboratory. Hopkinson's law, the magnetic counterpart to Ohm's law, is named after him. Life and career John Hopkinson was born in Manchester, the eldest of 5 children. His father, also called John, was a mechanical engineer. He was educated at Queenwood School in Hampshire and Owens College in Manchester. He won a scholarship to Trinity College, Cambridge in 1867 and graduated in 1871 as Senior Wrangler, having placed first in the demanding Cambridge Mathemati ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Induction Motors
An induction motor or asynchronous motor is an AC electric motor in which the electric current in the rotor needed to produce torque is obtained by electromagnetic induction from the magnetic field of the stator winding. An induction motor can therefore be made without electrical connections to the rotor. An induction motor's rotor can be either wound type or squirrel-cage type. Three-phase squirrel-cage induction motors are widely used as industrial drives because they are self-starting, reliable and economical. Single-phase induction motors are used extensively for smaller loads, such as household appliances like fans. Although traditionally used in fixed-speed service, induction motors are increasingly being used with variable-frequency drives (VFD) in variable-speed service. VFDs offer especially important energy savings opportunities for existing and prospective induction motors in variable-torque centrifugal fan, pump and compressor load applications. Squirrel-cage ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alternator
An alternator is an electrical generator that converts mechanical energy to electrical energy in the form of alternating current. For reasons of cost and simplicity, most alternators use a rotating magnetic field with a stationary armature.Gordon R. Selmon, ''Magnetoelectric Devices'', John Wiley and Sons, 1966 no ISBN pp. 391-393 Occasionally, a linear alternator or a rotating armature with a stationary magnetic field is used. In principle, any AC electrical generator can be called an alternator, but usually the term refers to small rotating machines driven by automotive and other internal combustion engines. An alternator that uses a permanent magnet for its magnetic field is called a magneto. Alternators in power stations driven by steam turbines are called turbo-alternators. Large 50 or 60 Hz three-phase alternators in power plants generate most of the world's electric power, which is distributed by electric power grids. History Alternating current generating ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electric Motor
An electric motor is an Electric machine, electrical machine that converts electrical energy into mechanical energy. Most electric motors operate through the interaction between the motor's magnetic field and electric current in a Electromagnetic coil, wire winding to generate force in the form of torque applied on the motor's shaft. An electric generator is mechanically identical to an electric motor, but operates with a reversed flow of power, converting mechanical energy into electrical energy. Electric motors can be powered by direct current (DC) sources, such as from batteries, or rectifiers, or by alternating current (AC) sources, such as a power grid, Inverter (electrical), inverters or electrical generators. Electric motors may be classified by considerations such as power source type, construction, application and type of motion output. They can be powered by AC or DC, be Brushed motor, brushed or Brushless motor, brushless, single-phase, Two-phase electric power, two-p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mikhail Dolivo-Dobrovolsky
Mikhail Osipovich Dolivo-Dobrovolsky (russian: Михаи́л О́сипович Доли́во-Доброво́льский; german: Michail von Dolivo-Dobrowolsky or ''Michail Ossipowitsch Doliwo-Dobrowolski''; – ) was a Russian Empire-born engineer, electrician, and inventor of Polish-Russian origins, active in the German Empire and also in Switzerland. After studying in Germany and while working in Berlin for ''Allgemeine Elektricitäts-Gesellschaft'' (AEG), he became one of the founders (the others were Nikola Tesla, Galileo Ferraris and Jonas Wenström) of polyphase electrical systems, developing the three-phase electrical generator and a three-phase electrical motor (1888) and studying star and delta connections. The triumph of the three-phase system was displayed in Europe at the International Electro-Technical Exhibition of 1891, where Dolivo-Dobrovolsky used this system to transmit electric power at the distance of 176 km with 75% efficiency. In 1891 he ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
