Misplaced Pages

#353646

92-670: Brush Electrical Machines is a manufacturer of electrical generators typically for gas turbine and steam turbine driven applications. The main office is based at Loughborough in Leicestershire , UK . Charles Francis Brush , born in Cleveland , Ohio in 1849, founded the Brush Electric Light Company, which stayed in business in the U.S. until 1889 when it was sold to the Thomson-Houston Company making Brush

184-459: A magnetic field , which allows objects to attract or repel each other. Because both electric currents and magnetic moments of elementary particles give rise to a magnetic field, magnetism is one of two aspects of electromagnetism . The most familiar effects occur in ferromagnetic materials, which are strongly attracted by magnetic fields and can be magnetized to become permanent magnets , producing magnetic fields themselves. Demagnetizing

276-425: A magnetic force microscope to reveal magnetic domain boundaries that resemble white lines in the sketch. There are many scientific experiments that can physically show magnetic fields. When a domain contains too many molecules, it becomes unstable and divides into two domains aligned in opposite directions so that they stick together more stably. When exposed to a magnetic field, the domain boundaries move, so that

368-635: 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 utility operation on the Moscow power system with a rating of 25 MW, the largest MHD plant rating in the world at that time. MHD generators operated as

460-698: A topping cycle are currently (2007) less efficient than combined cycle gas turbines . Induction AC motors may be used as generators, turning mechanical energy into electric current. Induction generators operate by mechanically turning their rotor faster than the simultaneous speed, giving negative slip. A regular AC non-simultaneous motor usually can be used as a generator, without any changes to its parts. Induction generators are useful in applications like minihydro power plants, wind turbines, or in reducing high-pressure gas streams to lower pressure, because they can recover energy with relatively simple controls. They do not require another circuit to start working because

552-479: A British electrician, J. E. H. Gordon , in 1882. The first public demonstration of an "alternator system" was given by William Stanley Jr. , an employee of Westinghouse Electric in 1886. Sebastian Ziani de Ferranti established Ferranti, Thompson and Ince in 1882, to market his Ferranti-Thompson Alternator , invented with the help of renowned physicist Lord Kelvin . His early alternators produced frequencies between 100 and 300 Hz . Ferranti went on to design

644-430: A crystalline solid. In an antiferromagnet , unlike a ferromagnet, there is a tendency for the intrinsic magnetic moments of neighboring valence electrons to point in opposite directions. When all atoms are arranged in a substance so that each neighbor is anti-parallel, the substance is antiferromagnetic . Antiferromagnets have a zero net magnetic moment because adjacent opposite moment cancels out, meaning that no field

736-436: A foot pump, such generators can be practically used to charge batteries, and in some cases are designed with an integral inverter. An average "healthy human" can produce a steady 75 watts (0.1 horsepower) for a full eight hour period, while a "first class athlete" can produce approximately 298 watts (0.4 horsepower) for a similar period, at the end of which an undetermined period of rest and recovery will be required. At 298 watts,

828-456: A generator and load is shown in the adjacent diagram. The generator is represented by an abstract generator consisting of an ideal voltage source and an internal impedance. The generator's V G {\displaystyle V_{\text{G}}} and R G {\displaystyle R_{\text{G}}} parameters can be determined by measuring the winding resistance (corrected to operating temperature ), and measuring

920-430: A generator consists of a rotating part and a stationary part which together form a magnetic circuit : One of these parts generates a magnetic field, the other has a wire winding in which the changing field induces an electric current: The armature can be on either the rotor or the stator, depending on the design, with the field coil or magnet on the other part. Before the connection between magnetism and electricity

1012-662: A magnet is also possible. Only a few substances are ferromagnetic; the most common ones are iron , cobalt , nickel , and their alloys. All substances exhibit some type of magnetism. Magnetic materials are classified according to their bulk susceptibility. Ferromagnetism is responsible for most of the effects of magnetism encountered in everyday life, but there are actually several types of magnetism. Paramagnetic substances, such as aluminium and oxygen , are weakly attracted to an applied magnetic field; diamagnetic substances, such as copper and carbon , are weakly repelled; while antiferromagnetic materials, such as chromium , have

SECTION 10

#1732855975354

1104-446: A magnetic field produces a current which changes direction with each 180° rotation, an alternating current (AC). However many early uses of electricity required direct current (DC). In the first practical electric generators, called dynamos , the AC was converted into DC with a commutator , a set of rotating switch contacts on the armature shaft. The commutator reversed the connection of

1196-402: A material is put in a magnetic field, the electrons circling the nucleus will experience, in addition to their Coulomb attraction to the nucleus, a Lorentz force from the magnetic field. Depending on which direction the electron is orbiting, this force may increase the centripetal force on the electrons, pulling them in towards the nucleus, or it may decrease the force, pulling them away from

1288-403: A million amperes , because the homopolar generator can be made to have very low internal resistance. A magnetohydrodynamic generator directly extracts electric power from moving 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

1380-496: A more complex relationship with a magnetic field. The force of a magnet on paramagnetic, diamagnetic, and antiferromagnetic materials is usually too weak to be felt and can be detected only by laboratory instruments, so in everyday life, these substances are often described as non-magnetic. The strength of a magnetic field always decreases with distance from the magnetic source, though the exact mathematical relationship between strength and distance varies. Many factors can influence

1472-511: A needle." The 11th-century Chinese scientist Shen Kuo was the first person to write—in the Dream Pool Essays —of the magnetic needle compass and that it improved the accuracy of navigation by employing the astronomical concept of true north . By the 12th century, the Chinese were known to use the lodestone compass for navigation. They sculpted a directional spoon from lodestone in such

1564-524: A paramagnetic substance, has unpaired electrons. However, in addition to the electrons' intrinsic magnetic moment's tendency to be parallel to an applied field, there is also in these materials a tendency for these magnetic moments to orient parallel to each other to maintain a lowered-energy state. Thus, even in the absence of an applied field, the magnetic moments of the electrons in the material spontaneously line up parallel to one another. Every ferromagnetic substance has its own individual temperature, called

1656-502: A permanent magnet that needs no power, an electromagnet requires a continuous supply of current to maintain the magnetic field. Electromagnets are widely used as components of other electrical devices, such as motors , generators , relays , solenoids, loudspeakers , hard disks , MRI machines , scientific instruments, and magnetic separation equipment. Electromagnets are also employed in industry for picking up and moving heavy iron objects such as scrap iron and steel. Electromagnetism

1748-416: A person's body. In ancient China , the earliest literary reference to magnetism lies in a 4th-century BC book named after its author, Guiguzi . The 2nd-century BC annals, Lüshi Chunqiu , also notes: "The lodestone makes iron approach; some (force) is attracting it." The earliest mention of the attraction of a needle is in a 1st-century work Lunheng ( Balanced Inquiries ): "A lodestone attracts

1840-577: A re-adjustment of Garzoni's work. Garzoni's treatise was known also to Giovanni Battista Della Porta . In 1600, William Gilbert published his De Magnete, Magneticisque Corporibus, et de Magno Magnete Tellure ( On the Magnet and Magnetic Bodies, and on the Great Magnet the Earth ). In this work he describes many of his experiments with his model earth called the terrella . From his experiments, he concluded that

1932-565: A result of elementary point charges moving relative to each other. Wilhelm Eduard Weber advanced Gauss's theory to Weber electrodynamics . From around 1861, James Clerk Maxwell synthesized and expanded many of these insights into Maxwell's equations , unifying electricity, magnetism, and optics into the field of electromagnetism . However, Gauss's interpretation of magnetism is not fully compatible with Maxwell's electrodynamics. In 1905, Albert Einstein used Maxwell's equations in motivating his theory of special relativity , requiring that

SECTION 20

#1732855975354

2024-478: A series of discoveries, the dynamo was succeeded by many later inventions, especially the AC alternator , which was capable of generating alternating current . It is commonly known to be the Synchronous Generators (SGs). The synchronous machines are directly connected to the grid and need to be properly synchronized during startup. Moreover, they are excited with special control to enhance the stability of

2116-487: A sliding magnet moves back and forth through a solenoid , a copper wire or a coil. An alternating current is induced in the wire, or loops of wire, by Faraday's law of induction each time the magnet slides through. This type of generator is used in the Faraday flashlight . Larger linear electricity generators are used in wave power schemes. Grid-connected generators deliver power at a constant frequency. For generators of

2208-434: A small DC voltage . This design was inefficient, due to self-cancelling counterflows of current in regions of the disk that were not under the influence of the magnetic field. While current was induced directly underneath the magnet, the current would circulate 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

2300-450: A stable power supply. Electric scooters with regenerative braking have become popular all over the world. Engineers use kinetic energy recovery systems on the scooter to reduce energy consumption and increase its range up to 40-60% by simply recovering energy using the magnetic brake, which generates electric energy for further use. Modern vehicles reach speed up to 25–30 km/h and can run up to 35–40 km. An engine-generator

2392-417: A water- or wind-powered generator to trickle-charge the batteries. A small propeller , wind turbine or turbine is connected to a low-power generator to supply currents at typical wind or cruising speeds. Recreational vehicles need an extra power supply to power their onboard accessories, including air conditioning units, and refrigerators. An RV power plug is connected to the electric generator to obtain

2484-592: A way that the handle of the spoon always pointed south. Alexander Neckam , by 1187, was the first in Europe to describe the compass and its use for navigation. In 1269, Peter Peregrinus de Maricourt wrote the Epistola de magnete , the first extant treatise describing the properties of magnets. In 1282, the properties of magnets and the dry compasses were discussed by Al-Ashraf Umar II , a Yemeni physicist , astronomer , and geographer . Leonardo Garzoni 's only extant work,

2576-570: A wealthy man. In 1880, the Anglo-American Brush Electric Light Corporation was established in Lambeth , London. Its formation was to exploit the invention of Brush's first electric dynamo in 1876. As the business grew, due to the demand for new electrical apparatus, larger premises were sought, and in 1889 the corporation moved 100 miles north into the newly acquired Falcon Engine and Car Works at Loughborough under

2668-562: Is an industrial facility that generates electricity . Most power stations contain one or more generators, or spinning machines converting mechanical power into three-phase electrical power . The relative motion between a magnetic field and a conductor creates an electric current . The energy source harnessed to turn the generator varies widely. Most power stations in the world burn fossil fuels such as coal , oil , and natural gas to generate electricity. Cleaner sources include nuclear power , and increasingly use renewables such as

2760-416: Is anti-aligned. This is called a canted antiferromagnet or spin ice and is an example of geometrical frustration . Like ferromagnetism, ferrimagnets retain their magnetization in the absence of a field. However, like antiferromagnets, neighboring pairs of electron spins tend to point in opposite directions. These two properties are not contradictory, because in the optimal geometrical arrangement, there

2852-497: Is impossible according to classical physics, and that a proper understanding requires a quantum-mechanical description. All materials undergo this orbital response. However, in paramagnetic and ferromagnetic substances, the diamagnetic effect is overwhelmed by the much stronger effects caused by the unpaired electrons. In a paramagnetic material there are unpaired electrons; i.e., atomic or molecular orbitals with exactly one electron in them. While paired electrons are required by

Brush Electrical Machines - Misplaced Pages Continue

2944-410: Is more magnetic moment from the sublattice of electrons that point in one direction, than from the sublattice that points in the opposite direction. Most ferrites are ferrimagnetic. The first discovered magnetic substance, magnetite , is a ferrite and was originally believed to be a ferromagnet; Louis Néel disproved this, however, after discovering ferrimagnetism. When a ferromagnet or ferrimagnet

3036-403: Is produced by them. Antiferromagnets are less common compared to the other types of behaviors and are mostly observed at low temperatures. In varying temperatures, antiferromagnets can be seen to exhibit diamagnetic and ferromagnetic properties. In some materials, neighboring electrons prefer to point in opposite directions, but there is no geometrical arrangement in which each pair of neighbors

3128-497: Is provided by one or more electromagnets, which are usually called field coils. 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 transformed to and from very high voltages to permit low losses over large distances. Through

3220-415: Is self- excited , i.e. its field electromagnets are powered by the machine's own output. Other types of DC generators use a separate source of direct current to energise their field magnets. A homopolar generator is a DC electrical generator comprising an electrically conductive disc or cylinder rotating in a plane perpendicular to a uniform static magnetic field. A potential difference is created between

3312-408: Is sufficiently small, it acts like a single magnetic spin that is subject to Brownian motion . Its response to a magnetic field is qualitatively similar to the response of a paramagnet, but much larger. Japanese physicist Yosuke Nagaoka conceived of a type of magnetism in a square, two-dimensional lattice where every lattice node had one electron. If one electron was removed under specific conditions,

3404-405: Is the ability to independently supply electricity, allowing the units to serve as backup power sources. A generator can also be driven by human muscle power (for instance, in field radio station equipment). Human powered electric generators are commercially available, and have been the project of some DIY enthusiasts. Typically operated by means of pedal power, a converted bicycle trainer, or

3496-485: Is the combination of an electrical generator and an engine ( prime mover ) mounted together to form a single piece of self-contained equipment. The engines used are usually piston engines, but gas turbines can also be used, and there are even hybrid diesel-gas units, called dual-fuel units. Many different versions of engine-generators are available – ranging from very small portable petrol powered sets to large turbine installations. The primary advantage of engine-generators

3588-696: The Curie temperature , or Curie point, above which it loses its ferromagnetic properties. This is because the thermal tendency to disorder overwhelms the energy-lowering due to ferromagnetic order. Ferromagnetism only occurs in a few substances; common ones are iron , nickel , cobalt , their alloys , and some alloys of rare-earth metals. The magnetic moments of atoms in a ferromagnetic material cause them to behave something like tiny permanent magnets. They stick together and align themselves into small regions of more or less uniform alignment called magnetic domains or Weiss domains . Magnetic domains can be observed with

3680-781: The Deptford Power Station for the London Electric Supply Corporation in 1887 using an alternating current system. On its completion in 1891, it was the first truly modern power station, supplying high-voltage AC power that was then "stepped down" for consumer use on each street. This basic system remains in use today around the world. After 1891, polyphase alternators were introduced to supply currents of multiple differing phases. 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 motors. As

3772-449: The Due trattati sopra la natura, e le qualità della calamita ( Two treatises on the nature and qualities of the magnet ), is the first known example of a modern treatment of magnetic phenomena. Written in years near 1580 and never published, the treatise had a wide diffusion. In particular, Garzoni is referred to as an expert in magnetism by Niccolò Cabeo, whose Philosophia Magnetica (1629) is just

Brush Electrical Machines - Misplaced Pages Continue

3864-519: The Earth was itself magnetic and that this was the reason compasses pointed north whereas, previously, some believed that it was the pole star Polaris or a large magnetic island on the north pole that attracted the compass. An understanding of the relationship between electricity and magnetism began in 1819 with work by Hans Christian Ørsted , a professor at the University of Copenhagen, who discovered, by

3956-506: The Greek term μαγνῆτις λίθος magnētis lithos , "the Magnesian stone, lodestone". In ancient Greece, Aristotle attributed the first of what could be called a scientific discussion of magnetism to the philosopher Thales of Miletus , who lived from about 625 BC to about 545 BC. The ancient Indian medical text Sushruta Samhita describes using magnetite to remove arrows embedded in

4048-466: The Pauli exclusion principle to have their intrinsic ('spin') magnetic moments pointing in opposite directions, causing their magnetic fields to cancel out, an unpaired electron is free to align its magnetic moment in any direction. When an external magnetic field is applied, these magnetic moments will tend to align themselves in the same direction as the applied field, thus reinforcing it. A ferromagnet, like

4140-569: The standard model . Magnetism, at its root, arises from three sources: The magnetic properties of materials are mainly due to the magnetic moments of their atoms ' orbiting electrons . The magnetic moments of the nuclei of atoms are typically thousands of times smaller than the electrons' magnetic moments, so they are negligible in the context of the magnetization of materials. Nuclear magnetic moments are nevertheless very important in other contexts, particularly in nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI). Ordinarily,

4232-668: The Air ), medical and other needs in remote stations and towns. A tachogenerator is an electromechanical device which produces an output voltage proportional to its shaft speed. It may be used for a speed indicator or in a feedback speed control system. Tachogenerators are frequently used to power tachometers to measure the speeds of electric motors, engines, and the equipment they power. Generators generate voltage roughly proportional to shaft speed. With precise construction and design, generators can be built to produce very precise voltages for certain ranges of shaft speeds. An equivalent circuit of

4324-469: The Falcon Works site, but throughout this period Brush Electrical Machines Ltd manufacturing generators and motors has always been the largest company. Over 5,000 staff were employed on the site during the 1960s and 70s. The following products are manufactured by Brush: In 2022, Brush Electrical Machines became a part of Baker Hughes. In 1915, Brush Electrical was one of a number of companies outside

4416-500: The accidental twitching of a compass needle near a wire, that an electric current could create a magnetic field. This landmark experiment is known as Ørsted's Experiment. Jean-Baptiste Biot and Félix Savart , both of whom in 1820 came up with the Biot–Savart law giving an equation for the magnetic field from a current-carrying wire. Around the same time, André-Marie Ampère carried out numerous systematic experiments and discovered that

4508-473: The armature winding to the circuit every 180° rotation of the shaft, creating a pulsing DC current. One of the first dynamos was built by Hippolyte Pixii in 1832. The dynamo was the first electrical generator capable of delivering power for industry. The Woolrich Electrical Generator of 1844, now in Thinktank, Birmingham Science Museum , is the earliest electrical generator used in an industrial process. It

4600-436: The armature winding. When the generator first starts to turn, the small amount of remanent magnetism present in the iron 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

4692-402: The assistance of power electronic devices, these can regulate the output frequency to a desired value over a wider range of generator shaft speeds. Alternatively, a standard generator can be used with no attempt to regulate frequency, and the resulting power converted to the desired output frequency with a rectifier and converter combination. Allowing a wider range of prime mover speeds can improve

SECTION 50

#1732855975354

4784-458: The average "healthy human" becomes exhausted within 10 minutes. The net electrical power that can be produced will be less, due to the efficiency of the generator. Portable radio receivers with a crank are made to reduce battery purchase requirements, see clockwork radio . During the mid 20th century, pedal powered radios were used throughout the Australian outback , to provide schooling ( School of

4876-409: The bicycle's tire on an as-needed basis, and hub dynamos which are directly attached to the bicycle's drive train. The name is conventional as they are small permanent-magnet alternators, not self-excited DC machines as are dynamos . Some electric bicycles are capable of regenerative braking , where the drive motor is used as a generator to recover some energy during braking. Sailing boats may use

4968-597: The center of the disc and the rim (or ends of the cylinder), the electrical polarity depending on the direction of rotation and the orientation of the field. It is also known as a unipolar generator , acyclic generator , disk dynamo , or Faraday 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. They are unusual in that they can produce tremendous electric current, some more than

5060-436: The copper disc. Later homopolar generators would solve this problem by using an array of magnets arranged 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 multiple turns of wire in a coil could produce higher, more useful voltages. Since

5152-407: The difficulty of insulating machines that produced very high voltages, electrostatic generators had low power ratings, and were never used for generation of commercially significant quantities of electric power. Their only practical applications were to power early X-ray tubes , and later in some atomic particle accelerators . The operating principle of electromagnetic generators was discovered in

5244-420: The domains aligned with the magnetic field grow and dominate the structure (dotted yellow area), as shown at the left. When the magnetizing field is removed, the domains may not return to an unmagnetized state. This results in the ferromagnetic material's being magnetized, forming a permanent magnet. When magnetized strongly enough that the prevailing domain overruns all others to result in only one single domain,

5336-416: The electrons preferentially adopt arrangements in which the magnetic moment of each electron is canceled by the opposite moment of another electron. Moreover, even when the electron configuration is such that there are unpaired electrons and/or non-filled subshells, it is often the case that the various electrons in the solid will contribute magnetic moments that point in different, random directions so that

5428-401: The enormous number of electrons in a material are arranged such that their magnetic moments (both orbital and intrinsic) cancel out. This is due, to some extent, to electrons combining into pairs with opposite intrinsic magnetic moments as a result of the Pauli exclusion principle (see electron configuration ), and combining into filled subshells with zero net orbital motion. In both cases,

5520-597: The established aviation contractors selected by the Royal Navy to receive orders for aircraft to meet the expanding needs of the Royal Naval Air Service . Brush completed 650 aircraft by the end of 1919, including 400 Avro 504s and 142 Short Type 184s . It also built de Havilland Dragon Rapides during the Second World War , taking over production from de Havilland in 1943 and building 346 aircraft (47.5% of

5612-413: The first major industrial uses of electricity. For example, in the 1870s Siemens used electromagnetic dynamos to power electric arc furnaces for the production of metals and other materials. The dynamo machine that was developed consisted of a stationary structure, which provides the magnetic field, and a set of rotating windings which turn within that field. On larger machines the constant magnetic field

SECTION 60

#1732855975354

5704-476: The generator reaches a steady state power output. Very large power station generators often utilize a separate smaller 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 fields of their largest generators, in order to restore customer power service. A dynamo uses commutators to produce direct current. It

5796-488: The lattice's energy would be minimal only when all electrons' spins were parallel. A variation on this was achieved experimentally by arranging the atoms in a triangular moiré lattice of molybdenum diselenide and tungsten disulfide monolayers. Applying a weak magnetic field and a voltage led to ferromagnetic behavior when 100-150% more electrons than lattice nodes were present. The extra electrons delocalized and paired with lattice electrons to form doublons. Delocalization

5888-408: The laws held true in all inertial reference frames . Gauss's approach of interpreting the magnetic force as a mere effect of relative velocities thus found its way back into electrodynamics to some extent. Electromagnetism has continued to develop into the 21st century, being incorporated into the more fundamental theories of gauge theory , quantum electrodynamics , electroweak theory , and finally

5980-434: The magnetic field are necessarily accompanied by a nonzero electric field, and propagate at the speed of light . In vacuum, where μ 0 is the vacuum permeability . In a material, The quantity μ 0 M is called magnetic polarization . If the field H is small, the response of the magnetization M in a diamagnet or paramagnet is approximately linear: the constant of proportionality being called

6072-430: The magnetic field of an object including the magnetic moment of the material, the physical shape of the object, both the magnitude and direction of any electric current present within the object, and the temperature of the object. Magnetism was first discovered in the ancient world when people noticed that lodestones , naturally magnetized pieces of the mineral magnetite , could attract iron. The word magnet comes from

6164-427: The magnetic field. The wire turns are often wound around a magnetic core made from a ferromagnetic or ferrimagnetic material such as iron ; the magnetic core concentrates the magnetic flux and makes a more powerful magnet. The main advantage of an electromagnet over a permanent magnet is that the magnetic field can be quickly changed by controlling the amount of electric current in the winding. However, unlike

6256-453: The magnetic force between two DC current loops of any shape is equal to the sum of the individual forces that each current element of one circuit exerts on each other current element of the other circuit. In 1831, Michael Faraday discovered that a time-varying magnetic flux induces a voltage through a wire loop. In 1835, Carl Friedrich Gauss hypothesized, based on Ampère's force law in its original form, that all forms of magnetism arise as

6348-409: The material is magnetically saturated . When a magnetized ferromagnetic material is heated to the Curie point temperature, the molecules are agitated to the point that the magnetic domains lose the organization, and the magnetic properties they cause cease. When the material is cooled, this domain alignment structure spontaneously returns, in a manner roughly analogous to how a liquid can freeze into

6440-402: The material will not be magnetic. Sometimes—either spontaneously, or owing to an applied external magnetic field—each of the electron magnetic moments will be, on average, lined up. A suitable material can then produce a strong net magnetic field. The magnetic behavior of a material depends on its structure, particularly its electron configuration , for the reasons mentioned above, and also on

6532-704: The new name, Brush Electrical Engineering Company Limited. In 1914, the company began manufacturing Ljungstrom steam turbines under licence. Over the next sixty years, the business grew by acquisitions, until in 1957, the Brush companies were incorporated into the Hawker Siddeley Group. Within the group, the company manufactured a vast range of electrical products, including turbo generators , salient pole machines, induction motors, traction motors and generators, traction locomotives, switchgear, transformers and fuses. In November 1991 Hawker Siddeley Electric Power Group

6624-461: The nucleus. This effect systematically increases the orbital magnetic moments that were aligned opposite the field and decreases the ones aligned parallel to the field (in accordance with Lenz's law ). This results in a small bulk magnetic moment, with an opposite direction to the applied field. This description is meant only as a heuristic ; the Bohr–Van Leeuwen theorem shows that diamagnetism

6716-436: The open-circuit and loaded voltage for a defined current load. This is the simplest model of a generator, further elements may need to be added for an accurate representation. In particular, inductance can be added to allow for the machine's windings and magnetic leakage flux, but a full representation can become much more complex than this. Magnetism Magnetism is the class of physical attributes that occur through

6808-413: 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. Independently of Faraday, Ányos Jedlik started experimenting in 1827 with the electromagnetic rotating devices which he called electromagnetic self-rotors . In the prototype of

6900-443: The overall energy production of an installation, at the cost of more complex generators and controls. For example, where a wind turbine operating at fixed frequency might be required to spill energy at high wind speeds, a variable speed system can allow recovery of energy contained during periods of high wind speed. A power station , also known as a power plant or powerhouse and sometimes generating station or generating plant ,

6992-419: The paramagnetic behavior dominates. Thus, despite its universal occurrence, diamagnetic behavior is observed only in a purely diamagnetic material. In a diamagnetic material, there are no unpaired electrons, so the intrinsic electron magnetic moments cannot produce any bulk effect. In these cases, the magnetization arises from the electrons' orbital motions, which can be understood classically as follows: When

7084-472: The power system. Alternating current generating systems were known in simple forms from Michael Faraday 's original discovery of the magnetic induction of electric current . Faraday himself built an early alternator. His machine was a "rotating rectangle", whose operation was heteropolar : each active conductor passed successively through regions where the magnetic field was in opposite directions. Large two-phase alternating current generators were built by

7176-399: The requirements for larger scale power generation increased, a new limitation rose: the magnetic fields available from permanent magnets. Diverting a small amount of the power generated by the generator to an electromagnetic field coil allowed the generator to produce substantially more power. This concept was dubbed self-excitation . The field coils are connected in series or parallel with

7268-653: The resulting theory ( electromagnetism ) is fully consistent with special relativity. In particular, a phenomenon that appears purely electric or purely magnetic to one observer may be a mix of both to another, or more generally the relative contributions of electricity and magnetism are dependent on the frame of reference. Thus, special relativity "mixes" electricity and magnetism into a single, inseparable phenomenon called electromagnetism , analogous to how general relativity "mixes" space and time into spacetime . All observations on electromagnetism apply to what might be considered to be primarily magnetism, e.g. perturbations in

7360-449: The single-pole electric starter (finished between 1852 and 1854) both the stationary and the revolving parts were electromagnetic. It was also the discovery of the principle of dynamo self-excitation , which replaced permanent magnet designs. He also may have formulated the concept of the dynamo in 1861 (before Siemens and Wheatstone ) but did not patent it as he thought he was not the first to realize this. A coil of wire rotating in

7452-510: The stator field. Wheatstone's design was similar to Siemens', with the difference that in the Siemens design the stator electromagnets were in series with the rotor, but in Wheatstone's design they were in parallel. The use of electromagnets rather than permanent magnets greatly increased the power output of a dynamo and enabled high power generation for the first time. This invention led directly to

7544-611: The sun , wind , waves and running water . Motor vehicles require electrical energy to power their instrumentation, keep the engine itself operating, and recharge their batteries. Until about the 1960s motor vehicles tended to use DC generators (dynamos) with electromechanical regulators. Following the historical trend above and for many of the same reasons, these have now been replaced by alternators with built-in rectifier circuits. Bicycles require energy to power running lights and other equipment. There are two common kinds of generator in use on bicycles: bottle dynamos which engage

7636-476: The synchronous or induction type, the primer mover speed turning the generator shaft must be at a particular speed (or narrow range of speed) to deliver power at the required utility frequency. Mechanical speed-regulating devices may waste a significant fraction of the input energy to maintain a required fixed frequency. Where it is impractical or undesired to tightly regulate the speed of the prime mover, doubly fed electric machines may be used as generators. With

7728-407: The temperature. At high temperatures, random thermal motion makes it more difficult for the electrons to maintain alignment. Diamagnetism appears in all materials and is the tendency of a material to oppose an applied magnetic field, and therefore, to be repelled by a magnetic field. However, in a material with paramagnetic properties (that is, with a tendency to enhance an external magnetic field),

7820-607: The total number produced) by the time production ended in 1945. Electrical generators In addition to electricity- and motion-based designs, photovoltaic and fuel cell powered generators use solar power and hydrogen-based fuels, respectively, to generate electrical output. The reverse conversion of electrical energy into mechanical energy is done by an electric motor , and motors and generators are very similar. Many motors can generate electricity from mechanical energy. Electromagnetic generators fall into one of two broad categories, dynamos and alternators. Mechanically,

7912-421: The turning magnetic field is provided by induction from the one they have. They also do not require speed governor equipment as they inherently operate at the connected grid frequency. An induction generator must be powered with a leading voltage; this is usually done by connection to an electrical grid, or by powering themselves with phase correcting capacitors. In the simplest form of linear electric generator,

8004-409: The years of 1831–1832 by Michael Faraday . The principle, later called Faraday's law , is that an electromotive force is generated in an electrical conductor which encircles a varying magnetic flux . Faraday 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

8096-452: Was discovered in 1820. As a consequence of Einstein's theory of special relativity , electricity and magnetism are fundamentally interlinked. Both magnetism lacking electricity, and electricity without magnetism, are inconsistent with special relativity, due to such effects as length contraction , time dilation , and the fact that the magnetic force is velocity-dependent. However, when both electricity and magnetism are taken into account,

8188-429: Was discovered, electrostatic generators were invented. They operated on electrostatic principles, by using moving electrically charged belts, plates and disks that carried charge to a high potential electrode. The charge was generated using either of two mechanisms: electrostatic induction or the triboelectric effect . Such generators generated very high voltage and low current . Because of their inefficiency and

8280-435: Was prevented unless the lattice electrons had aligned spins. The doublons thus created localized ferromagnetic regions. The phenomenon took place at 140 millikelvins. An electromagnet is a type of magnet in which the magnetic field is produced by an electric current . The magnetic field disappears when the current is turned off. Electromagnets usually consist of a large number of closely spaced turns of wire that create

8372-624: Was subject to a successful hostile takeover bid of £1.5 billion from BTR plc , a large engineering conglomerate. In November 1996 the FKI Group of Companies acquired the Hawker Siddeley Electric Power Group from BTR for a price of £182 million. On 1 July 2008 Melrose plc , a specialist investor in the manufacturing industry, bought FKI. During the last 125 years, various Brush companies (Brush Switchgear, Brush Transformers , Brush Traction and Brush Control Gear) have existed on

8464-590: Was used by the firm of Elkingtons for commercial electroplating . The modern dynamo, fit for use in industrial applications, was invented independently by Sir Charles Wheatstone , Werner von Siemens and Samuel Alfred Varley . Varley took out a patent on 24 December 1866, while Siemens and Wheatstone both announced their discoveries on 17 January 1867 by delivering papers at the Royal Society . The "dynamo-electric machine" employed self-powering electromagnetic field coils rather than permanent magnets to create

#353646