Electric Generator Essay Example for Free

electric automobile automobile Generator EssayEarly 20th century alternator do inBudapest, Hungary, in the agent generating h every of a hydroelectric station In electrical energy generation, an electric writer is a device that converts mechanised free energy to electrical energy. A beginning forces electric constitute (usually carried by electrons) to f low by an orthogonal electrical circuit. The citation of mechanical energy may be a reciprocating or turbine steam engine, water move finished a turbine or waterwheel, aninternal combustion engine, a wind turbine, a hand crank, compressed air, or either opposite source of mechanical energy. Generators supply almost all of the cater for the electric federal agency storage-battery grids which provide most of the worlds electric military groupfulness. The reverse conversion of electrical energy into mechanical energy is done by an electric ride, and motors and seeds have umteen similarities. Many motors ca n be automatically driven to take electricity and frequently make acceptable roots.HistoryBefore the connection in the midst of drawism and electricity was discovered, static generators were used. They operated on electrostaticprinciples. Such generators generated very high voltage and low current. They operated by using base electrically charged belts, plates, and disks that carried charge to a high potential electrode. The charge was generated using either of both mechanisms* Electrostatic instalment* The triboelectric effect, where the contact between two insulators leaves them charged. Be puzzle of their inefficiency and the difficulty of insulating weapons that produced very high voltages, electrostatic generators had low power ratings, and were never used for generation of commercially significant quantities of electric power. The Wimshurst machine and forefront de Graaff generator atomic number 18 examples of these machines that have survived. In 1827, Hungarian A nyos Jedlik started expe lineenting with the electro magnetized rotating devices which he called electro magnetized self-rotors, nowadays called the Jedliks dynamo.In the paradigm of the single-pole electric starter (finished between 1852 and 1854) both the stationary and the revolving parts were electromagnetic. He formulated the concept of the dynamo at least 6 years beforeSiemens and Wheatst cardinal completely if didnt patent it as he view he wasnt the prime(prenominal) to realize this. In essence the concept is that instead of permanent magnets, two electromagnets opposite to each other induce the magnetic field around the rotor. It was as well as the discovery of the principle of self-excitation.1Faraday disk, the starting time electric generator. The horseshoe-shaped magnet (A) created a magnetic field through the disk (D). When the disk was turned, this generate an electric current radially outward from the center toward the rim. The current flowed out through the sli ding spring contact m, through the external circuit, and back into the center of the disk through the axle. In the years of 18311832, Michael Faraday discovered the operating principle of electromagnetic generators. The principle, later called Faradays law, is that an electromotive force is generated in an electrical conductor which encircles a variable magnetic flux. He also built the first electromagnetic generator, called the Faraday disk, a type of homopolar generator, using a copper disc rotating between the poles of a horseshoe magnet. It produced a small DC voltage.This design was inefficient, due to self-cancelling counterflows of current in regions that were non under the figure out of the magnetic field. While current was induced directly underneath the magnet, the current would sprinkle backwards in regions that were outside the influence of the magnetic field. This counterflow limited the power output to the pickup wires, and induced waste heating of the copper disc. subsequently homopolar generators would solve this problem by using an array of magnets logical around the disc perimeter to maintain a steady field effect in one current-flow direction.Another disadvantage was that the output voltage was very low, due to the single current path through the magnetic flux. Experimenters found that using fivefold turns of wire in a coil could produce higher, more than useful voltages. Since the output voltage is proportional to the number of turns, generators could be easily designed to produce any desired voltage by varying the number of turns. Wire windings became a basic feature of all subsequent generator designs.Dynamos ar no longer used for power generation due to the size and complexity of the commutator needed for high power applications. This thumping belt-driven high-current dynamo produced 310 amperes at 7 volts, or 2,170 watts, when spinning at 1400 RPM.Dynamo Electric Machine End View, Partly Section (U.S. Patent 284,110) The dyna mo was the first electrical generator capable of delivering power for industry. The dynamo uses electromagnetic stimulus generalization to convert mechanical rotation into direct currentthrough the use of a commutator. The first dynamo was built by Hippolyte Pixii in 1832. A dynamo machine consists of a stationary structure, which provides a constant magnetic field, and a typeset of rotating windings which turn within that field. On small machines the constant magnetic field may be provided by one or more permanent magnets medium- sizabler machines have the constant magnetic field provided by one or more electromagnets, which are usually called field coils. Through a serial of accidental discoveries, the dynamo became the source of many later inventions, including the DC electric motor, the AC alternator, the AC synchronous motor, and the rotary converter. jump current generating systems were known in simple forms from the discovery of the magnetic induction of electric current. The early machines were au becausetic by pioneers such as Michael Faraday and Hippolyte Pixii. Faraday developed the rotating rectangle, whose operation was heteropolar each active conductor passed successively through regions where the magnetic field was in opposite directions.2 The first public induction of a more productive alternator system took place in 1886.3 Large two- mannikin alternating current generators were built by a British electrician, J.E.H. Gordon, in 1882. Lord Kelvin andSebastian Ferranti also developed early alternators, producing frequencies between 100 and 300 Hz. In 1891, Nikola Tesla patented a practical high- absolute frequency alternator (which operated around 15 kHz).4After 1891, polyphase alternators were introduced to supply currents of multiple differing phases.5 Later alternators were designed for varying alternating-current frequencies between sixteen and about one hundred hertz, for use with arc lighting, incandescent lighting and electric moto rs.6 Large power generation dynamos are now rarely seen due to the now nearly universal use of alternating current for power distribution. Before the adoption of AC, very large direct-current dynamos were the only means of power generation and distribution. AC has come to dominate due to the ability of AC to be easily converted to and from very high voltages to permit low losses over large distances. Electromagnetic generatorsDynamo primary(prenominal) article DynamoDynamo Electric Machine (end view, partly section, U.S. Patent 284,110) A dynamo is an electrical generator that produces direct current with the use of a commutator. Dynamos were the first electrical generators capable of delivering power for industry, and the foundation upon which many other later electric-power conversion devices were establish, including the electric motor, the alternating-current alternator, and the rotary converter. Today, the simpler alternator dominates large scale power generation, for efficien cy, reliability and toll reasons. A dynamo has the disadvantages of a mechanical commutator. Also, converting alternating to direct current using power rectification devices (vacuum supply or more recently solid call down) is effective and usually economic.AlternatorMain article AlternatorWithout a commutator, a dynamo becomes an alternator, which is a synchronous singly feed generator. Alternators produce alternating current with a frequency that is based on the rotational facilitate of the rotor and the number of magnetic poles. Automotive alternators produce a varying frequency that changes with engine speed, which is then converted by a rectifier to DC. By comparison, alternators used to feed an electric power grid are generally operated at a speed very close to a specific frequency, for the benefit of AC devices that regulate their speed and performance based on grid frequency. round devices such as incandescent lamps and ballast-operated fluorescent lamps do not require a constant frequency, but synchronous motors such as in electric wall clocks do require a constant grid frequency.When attached to a larger electric grid with other alternators, an alternator will dynamically interact with the frequency already present on the grid, and operate at a speed that matches the grid frequency. If no driving power is applied, the alternator will continue to spin at a constant speed anyway, driven as a synchronous motor by the grid frequency. It is usually necessary for an alternator to be accelerated up to the correct speed and phase alignment before connecting to the grid, as any twin in frequency will cause the alternator to act as a synchronous motor, and suddenly rise to the correct phase alignment as it absorbs a large inrush current from the grid, which may upon the rotor and other equipment.Typical alternators use a rotating field winding excited with direct current, and a stationary (stator) winding that produces alternating current. Since the ro tor field only requires a tiny fraction of the power generated by the machine, the brushes for the field contact can be relatively small. In the grapheme of a brushless exciter, no brushes are used at all and the rotor shaft carries rectifiers to excite the main field winding. edit inference generatorMain article induction generatorAn induction generator or asynchronous generator is a type of AC electrical generator that uses the principles of induction motors to produce power. Induction generators operate by mechanically turning their rotor faster than the synchronous speed, giving ostracize slip. A regular AC asynchronous motor usually can be used as a generator, without any internal modifications. Induction generators are useful in applications such as minihydro power plants, wind turbines, or in simplification high-pressure gas streams to lower pressure, because they can recover energy with relatively simple controls. To operate an induction generator must be excited with a le ading voltage this is usually done by connection to an electrical grid, or sometimes they are self excited by using phase correcting capacitors. editMHD generatorMain article MHD generatorA magnetohydrodynamic generator directly extracts electric power from pitiable hot gases through a magnetic field, without the use of rotating electromagnetic machinery. MHD generators were originally developed because the output of a plasma MHD generator is a flame, well able to heat the boilers of a steam power plant. The first practical design was the AVCO Mk. 25, developed in 1965. The U.S. government funded substantial development, culminating in a 25 MW demonstration plant in 1987. In the Soviet Union from 1972 until the late 1980s, the MHD plant U 25 was in regular commercial operation on the Moscow power system with a rating of 25 MW, the largest MHD plant rating in the world at that time.7 MHD generators operated as a topping cycle are currently (2007) less efficient than combined cycle g as turbines. editOther rotating electromagnetic generatorsOther types of generators, such as the asynchronous or induction singly fed generator, the twice fed generator, or the brushless wound-rotor doubly fed generator, do not incorporate permanent magnets or field windings that establish a constant magnetic field, and as a result, are seeing success in variable speed constant frequency applications, such as wind turbines or otherrenewable energy technologies. The full output performance of any generator can be optimized with electronic control but only the doubly fed generators or the brushless wound-rotor doubly fed generator incorporate electronic control with power ratings that are substantially less than the power output of the generator under control, a feature which, by itself, offers cost, reliability and efficiency benefits.Homopolar generatorMain article Homopolar generatorFaraday disk, the first homopolar generatorA homopolar generator is a DC electrical generator compr ising an electrically conductive disc or cylinder rotating in a plane perpendicular to a uniform static magnetic field. A potential difference is created between the center of the disc and the rim (or ends of the cylinder), the electrical polaritydepending on the direction of rotation and the orientation of the field. It is also known as a unipolar generator, acyclic generator, disk dynamo, orFaraday disc. The voltage is typically low, on the order of a few volts in the case of small demonstration models, but large research generators can produce hundreds of volts, and some systems have multiple generators in series to produce an even larger voltage.8 They are unusual in that they can source tremendous electric current, some more than a million amperes, because the homopolar generator can be made to have very low internal resistance.ExcitationA small early 1900s 75 KVA direct-driven power station AC alternator, with a separate belt-driven exciter generator. Main article Excitation ( magnetic) An electric generator or electric motor that uses field coils rather than permanent magnets requires a current to be present in the field coils for the device to be able to work. If the field coils are not powered, the rotor in a generator can spin without producing any usable electrical energy, while the rotor of a motor may not spin at all. Smaller generators are sometimes self-excited, which means the field coils are powered by the current produced by the generator itself. The field coils are connected in series or parallel with the armature winding.When the generator first starts to turn, the small amount of remanent magnetism present in the squeeze core provides a magnetic field to get it started, generating a small current in the armature. This flows through the field coils, creating a larger magnetic field which generates a larger armature current. This bootstrap process continues until the magnetic field in the core levels off due to saturation and the generator r eaches a steady state power output. Very large power station generators often utilize a separate little generator to excite the field coils of the larger. In the event of a severe widespread power outage where islanding of power stations has occurred, the stations may need to perform a black start to excite the field of their largest generators, in order to restore customer power service.Electrostatic generatorMain article electrostatic generatorA Van de Graaff generator, for class room demonstrationsAn electrostatic generator, or electrostatic machine, is a mechanical device that produces static electricity, or electricity at high voltage and lowcontinuous current. The knowledge of static electricity dates back to the earliest civilizations, but for millennia it remained merely an interesting and mystifying phenomenon, without a theory to explain its style and often confused with magnetism. By the end of the 17th Century, researchers had developed practical means of generating el ectricity by friction, but the development of electrostatic machines did not begin in earnest until the 18th century, when they became fundamental instruments in the studies about the new science of electricity.Electrostatic generators operate by using manual (or other) power to transform mechanical work into electric energy. Electrostatic generators develop electrostatic charges of opposite signs rendered to two conductors, using only electric forces, and work by using moving plates, drums, or belts to carry electric charge to a high potentialelectrode. The charge is generated by one of two methods either the triboelectric effect (friction) or electrostatic induction. editWimshurst machineMain article Wimshurst machineWimshurst machine with two Leyden jars.Suppose that the conditions are as in the figure, with the segment A1 positive degree and the segment B1 negative. Now, as A1 moves to the left and B1 to the right, their potentials will rise on account of the work done in separ ating them against attraction. When A1 and neighboring sectors comes opposite the segment B2 of the B plate, which is now in contact with the brush Y, they will cause a displacement of electricity along the conductor between Y and Y1 bringing a negative charge, larger than the positive charge in A1 alone, on Y and sending a positive charge to the segment touching Y1.As A1 moves on, it passes near the brush Z and is partially discharged into the external circuit. It then passes on until, on touching the brush X, has a new charge, this time negative, driven into it by induction from B2 and neighboring sectors. As the machine turns, the process causes exponential increases in the voltages on all positions, until sparking occurs limiting the increase. The Wimshurst influence machine is an electrostatic generator, a machine for generating high voltages developed between 1880 and 1883 by Britishinventor James Wimshurst (18321903). It has a distinctive appearance with two large contra-rota ting discs mounted in a vertical plane, two go across bars with alloylic brushes, and a spark gap formed by two metal spheres.Van de Graaff generatorMain article Van de Graaff generatorA Van de Graaff generator is an electrostatic generator which uses a moving belt to accumulate very high voltages on a hollow metal globe on the top of the stand. It was invented by American physicist Robert J. Van de Graaff in 1929. The potential difference achieved in modern Van de Graaff generators can reach 5 megavolts. The Van de Graaff generator can be thought of as a constant-current source connected in parallel with a capacitorand a very large electrical resistance, so it can produce a visible electrical discharge to a close grounding surface which can potentially cause a spark depending on the voltage.