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Encyclopedia > Electrical generator
Early 20th century alternator made in Budapest, Hungary, in the power generating hall of a hydroelectric station

Electrostatic generators are used for scientific experiments requiring high voltages. Because of the difficulty of insulating machines producing very high voltages, electrostatic generators are made only with low power ratings and are never used for generation of commercially-significant quantities of electric power. Before the connection between magnetism and electricity was discovered, generators used electrostatic principles. The Wimshurst machine used electrostatic induction or "influence". Some electrostatic machines (such as the more modern Van de Graaff generator) uses either of two mechanisms: An electrostatic generator, or electrostatic machine, is a mechanical device that produces static electricity, or electricity at high voltage and low continuous current. ... This article or section is in need of attention from an expert on the subject. ... For other senses of this word, see magnetism (disambiguation). ... Electricity (from New Latin Ä“lectricus, amberlike) is a general term for a variety of phenomena resulting from the presence and flow of electric charge. ... Wimshurst machine with two Leyden jars. ... Van de Graf generator. ...

• Charge transferred from a high-voltage electrode
• Charge created by the triboelectric effect using the separation of two insulators (the belt leaving the lower pulley)

The triboelectric effect is a type of contact electrification in which certain materials become electrically charged after they come into contact with another different material and are then separated (such as through rubbing). ... This article or section is in need of attention from an expert on the subject. ...

In 1831-1832 Michael Faraday discovered that a potential difference is generated between the ends of an electrical conductor that moves perpendicular to a magnetic field. He also built the first electromagnetic generator called the 'Faraday disc', a type of homopolar generator, using a copper disc rotating between the poles of a horseshoe magnet. It produced a small DC voltage, and large amounts of current. Leopold I 1831 (MDCCCXXXI) was a common year starting on Saturday (see link for calendar). ... Year 1832 (MDCCCXXXII) was a leap year starting on Sunday (link will display the full calendar) of the Gregorian Calendar (or a leap year starting on Friday of the 12-day slower Julian calendar). ... Michael Faraday, FRS (September 22, 1791 â€“ August 25, 1867) was an English chemist and physicist (or natural philosopher, in the terminology of that time) who contributed to the fields of electromagnetism and electrochemistry. ... Potential difference is a quantity in physics related to the amount of energy that would be required to move an object from one place to another against various types of force. ... Magnetic field lines shown by iron filings In physics, the space surrounding moving electric charges, changing electric fields and magnetic dipoles contains a magnetic field. ... A homopolar generator, also known as a unipolar generator, acyclic generator, or disk dynamo, is an electrical generator in which the magnetic field has the same polarity at every point, so that the armature passes through the magnetic field lines of force continually in the same direction. ... For other uses, see Copper (disambiguation). ... For other uses, see Magnet (disambiguation). ...

### Dynamo

The Dynamo was the first electrical generator capable of delivering power for industry. The dynamo uses electromagnetic principles to convert mechanical rotation into a pulsing direct electric current through the use of a commutator. A dynamo machine consists of a stationary structure, which provides a constant magnetic field, and a set of rotating windings which turn within that field. On small machines the constant magnetic field may be provided by one or more permanent magnets; larger machines have the constant magnetic field provided by one or more electromagnets, which are usually called field coils. Electromagnetism is the physics of the electromagnetic field: a field which exerts a force on particles that possess the property of electric charge, and is in turn affected by the presence and motion of those particles. ... In electricity, current refers to electric current, which is the flow of electric charge. ... Conventional continuous current flows from the battery. ...

The first dynamo based on Faraday's principles was built in 1832 by Hippolyte Pixii, a French instrument maker. It used a permanent magnet which was rotated by a crank. The spinning magnet was positioned so that its north and south poles passed by a piece of iron wrapped with wire. Pixii found that the spinning magnet produced a pulse of current in the wire each time a pole passed the coil. Furthermore, the north and south poles of the magnet induced currents in opposite directions. By adding a commutator, Pixii was able to convert the alternating current to direct current. Year 1832 (MDCCCXXXII) was a leap year starting on Sunday (link will display the full calendar) of the Gregorian Calendar (or a leap year starting on Friday of the 12-day slower Julian calendar). ... Hippolyte Pixii (1808 - 1835) was an instrument maker from Paris, France. ... Conventional continuous current flows from the battery. ... City lights viewed in a motion blurred exposure. ... Direct current (DC or continuous current) is the continuous flow of electricity through a conductor such as a wire from high to low potential. ...

Unlike the Faraday disc, many turns of wire connected in series can be used in the moving windings of a dynamo. This allows the terminal voltage of the machine to be higher than a disc can produce, so that electrical energy can be delivered at a convenient voltage.

#### Reversible power conversion

 The relationship between mechanical rotation and electric current in a dynamo is reversible; the principles of the electric motor were discovered when it was found that one dynamo could cause a second interconnected dynamo to rotate if current was fed through it. The transformative ability of a dynamo to change energy from electrical power to mechanical power and back again could be exploited as a current-compensation and balancing device to even out power distribution on interconnected, unbalanced circuits. Two dynamos acting on each other to balance power differences between two loads. The two separate dynamos can be merged together into a single frame.

Image File history File links Size of this preview: 800 Ã— 502 pixelsFull resolution (1003 Ã— 629 pixel, file size: 37 KB, MIME type: image/png) This is an example of how two dynamos can be connected to each other to balance out the load across a split-field transformer. ... Image File history File links Size of this preview: 800 Ã— 502 pixelsFull resolution (1003 Ã— 629 pixel, file size: 37 KB, MIME type: image/png) This is an example of how two dynamos can be connected to each other to balance out the load across a split-field transformer. ...

### Jedlik's dynamo

 In 1827, Hungarian Anyos Jedlik started experimenting with electromagnetic rotating devices which he called electromagnetic self-rotors. In the prototype 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 before Siemens and Wheatstone. In essence the concept is that instead of permanent magnets, two electromagnets opposite to each other induce the magnetic field around the rotor. Ányos Jedlik's single pole electric starter (dynamo) (1861)

This article or section does not cite any references or sources. ... Anyos Jedlik (Hungarian Jedlik IstvÃ¡n Ãnyos, Slovak Å tefan AniÃ¡n JedlÃ­k) (January 11, 1800, SzimÅ‘ (now ZemnÃ© in Slovakia) -December 13, 1895,GyÃµr, Hungary) was a Hungarian inventor, engineer, physicist, and Roman Catholic Priest of Slovak origin. ... Werner von Siemens Ernst Werner von Siemens (known as Werner von Siemens) (December 13, 1816 â€“ December 6, 1892) was a German inventor and industrialist. ... Charles Wheatstone Sir Charles Wheatstone (February 6, 1802 - October 19, 1875) was the British inventor of many innovations including the English concertina the Stereoscope an early form of microphone the Playfair cipher (named for Lord Playfair, the person who publicized it) He was a major figure in the development of... Image File history File links Jedlikdynamo. ... Image File history File links Jedlikdynamo. ... Year 1861 (MDCCCLXI) was a common year starting on Tuesday (link will display the full calendar) of the Gregorian calendar (or a common year starting on Sunday of the 12-day slower Julian calendar). ...

### Gramme dynamo

Both of these designs suffered from a similar problem: they induced "spikes" of current followed by none at all. Antonio Pacinotti, an Italian scientist, fixed this by replacing the spinning coil with a toroidal one, which he created by wrapping an iron ring. This meant that some part of the coil was continually passing by the magnets, smoothing out the current. Zénobe Gramme reinvented this design a few years later when designing the first commercial power plants, which operated in Paris in the 1870s. His design is now known as the Gramme dynamo. Various versions and improvements have been made since then, but the basic concept of a spinning endless loop of wire remains at the heart of all modern dynamos. The Gramme dynamo was an electrical generator patented in 1870 by Belgian engineer Zénobe Gramme (April 4, 1826 - January 20, 1901). ... Antonio Pacinotti (Pisa, June 7, 1841 - Pisa, May 22, 1912) was a Professor of Physics at the University of Pisa. ... A toroid is a doughnut-shaped object whose surface is a torus. ... ZÃ©nobe Gramme, by Mathurin Moreau ZÃ©nobe ThÃ©ophile Gramme (April 4, 1826 - January 20, 1901) was a Belgian electrical engineer. ... This article is about the capital of France. ... // The invention of the telephone (1876) by Alexander Graham Bell. ... The Gramme dynamo was an electrical generator patented in 1870 by Belgian engineer Zénobe Gramme (April 4, 1826 - January 20, 1901). ...

### Other Rotating Electromagnetic Generators

Without a commutator, the dynamo is an example of an alternator, which is a synchronous singly-fed generator. With an electromechanical commutator, the dynamo is a classical direct current (DC) generator. The alternator must always operate at a constant speed that is precisely synchronized to the electrical frequency of the power grid for non-destructive operation. The DC generator can operate at any speed within mechanical limits but always outputs a direct current waveform. Conventional continuous current flows from the battery. ... Singly-Fed Electric Machines (i. ...

Other types of generators, such as the asynchronous or induction singly-fed generator, the doubly-fed generator, or the brushless wound-rotor doubly-fed generator, do not incorporate permanent magnets or field windings (i.e, electromagnets) that establish a constant magnetic field, and as a result, are seeing success in variable speed constant frequency applications, such as wind turbines or other renewable energy techologies. Singly-Fed Electric Machines (i. ... Doubly-fed electric machines (i. ... The Brushless wound-rotor [synchronous] doubly-fed electric machine (i. ... This article is about the machine for converting the kinetic energy in the wind into mechanical energy. ... Renewable energy effectively utilizes natural resources such as sunlight, wind, tides and geothermal heat, which are naturally replenished. ...

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, which by itself offer cost, reliability and efficiency benefits. Doubly-fed electric machines (i. ... The Brushless wound-rotor [synchronous] doubly-fed electric machine (i. ...

### MHD generator

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 a steam power plant. The first practical design was the AVCO Mk. 25, developed in 1965. The U.S. government performed substantial development, culminating in a 25Mw demonstration plant in 1987. MHD generators operated as a topping cycle are currently (2007) less efficient than combined-cycle gas turbines. // The MHD (magnetohydrodynamic) generator or dynamo transforms thermal energy or kinetic energy directly into electricity. ... The Rankine cycle is a thermodynamic cycle. ... A power station (also power plant) is a facility for the generation of electric power. ... Combined cycle is a term used when a power producing engine or plant employs more than one thermodynamic cycle. ... The worlds first commercial, oil-free gas turbine is manufactured by Capstone. ...

## Concepts

The generator moves an electric current, but does not create electric charge, which is already present in the conductive wire of its windings. It is somewhat analogous to a water pump, which creates a flow of water but does not create the water inside. Other types of electrical generators exist, based on other electrical phenomena such as piezoelectricity, and magnetohydrodynamics. The construction of a dynamo is similar to that of an electric motor, and all common types of dynamos could work as motors. Electrical phenomena are commonplace and unusual events that can be observed which illuminate the principles of the physics of electricity and are explained by them. ... Piezoelectricity is the ability of some materials (notably crystals and certain ceramics) to generate an electric potential[1] in response to applied mechanical stress. ... Magnetohydrodynamics (MHD) (magnetofluiddynamics or hydromagnetics) is the academic discipline which studies the dynamics of electrically conducting fluids. ... For other kinds of motors, see motor. ...

## Excitation

A generator that uses field coils instead of permanent magnets requires a current flow to be present in the field coils for the generator to be able to produce any power at all. If the field coils are not powered, the rotor can spin without the generator producing any usable electrical energy.

For older and very large power generating equipment, it has been traditionally necessary for a small separate exciter generator to be operated in conjunction with the main power generator. This is a small permanent-magnet generator which produces the constant current flow necessary for the larger generator to function.

Most modern generators with field coils feature a capability known as self-excitation where some of the power output from the rotor is diverted to power the field coils. Additionally the rotor or stator contains a small amount of magnetizable metal, which retains a very weak residual magnetism when the generator is turned off. The generator is turned on with no load connected, and the initial weak field creates a weak flow in the field coils, which in turn begins to slightly affect the rotor to begin to produce current that then further strengthens the field. This feedback loop continues to increase field voltage and output power until the generator reaches its full operating output level.

This initial self-excitation feedback process does not work if the generator is started connected to a load, as the load will quickly dissipate the slight power production of the initial field buildup process.

It is additionally possible for a self-exciting generator either turned off or started with a load connected to result in dissipation of the residual magnetic field, resulting in complete non-function of the generator. In the case of a 220v portable generator commonly used by consumers and construction contractors, this loss of the residual field can usually be remedied by shutting down the generator, disconnecting all loads, and connecting what are normally the high-voltage/amperage generator outputs to the terminals of a common 9-volt battery. This very small current flow from the battery (in comparison with normal generator output) is enough to restore the residual self-exciting magnetic field. Usually only a moment of current flow, just briefly touching across the battery terminals, is enough to restore the field.

## Terminology

The parts of a dynamo or related equipment can be expressed in either mechanical terms or electrical terms. Although distinctly separate, these two sets of terminology are frequently used interchangeably or in combinations that include one mechanical term and one electrical term. This causes great confusion when working with compound machines such as a brushless alternator or when conversing with people who work on a machine that is configured differently than the machines that the speaker is used to.

Mechanical

• Rotor: The rotating part of an alternator, generator, dynamo or motor.
• Stator: The stationary part of an alternator, generator, dynamo or motor.

Electrical

• Armature: The power-producing component of an alternator, generator, dynamo or motor. The armature can be on either the rotor or the stator.
• Field: The magnetic field component of an alternator, generator, dynamo or motor. The magnetic field of the dynamo or alternator can be provided by either electromagnets or permanent magnets mounted on either the rotor or the stator.

## Equivalent circuit

Equivalent circuit of generator and load.
G = generator
VG=generator open-circuit voltage
RG=generator internal resistance

The equivalent circuit of a generator and load is shown in the diagram to the right. To determine the generator's VG and RG parameters, follow this procedure: - Generator and load equivalent circuit. ... Generator and load equivalent circuit. ...

• Before starting the generator, measure the resistance across its terminals using an ohmmeter. This is its DC internal resistance RGDC.
• Start the generator. Before connecting the load RL, measure the voltage across the generator's terminals. This is the open-circuit voltage VG.
• Connect the load as shown in the diagram, and measure the voltage across it with the generator running. This is the on-load voltage VL.
• Measure the load resistance RL, if you don't already know it.
• Calculate the generator's AC internal resistance RGAC from the following formula:

$R_{GAC} = {R_L} left( {{{V_G}over{V_L}}-1} right)$ An Ohmmeter is an electrical measuring instrument that measures electrical resistance, the opposition to the flow of an electric current. ...

Note 1: The AC internal resistance of the generator when running is generally slightly higher than its DC resistance when idle. The above procedure allows you to measure both values. For rough calculations, you can omit the measurement of RGAC and assume that RGAC and RGDC are equal.

Note 2: If the generator is an AC type (distinctly not a dynamo), use an AC voltmeter for the voltage measurements.

### Maximum power

The maximum power theorem applies to generators as it does to any source of electrical energy. This theorem states that the maximum power can be obtained from the generator by making the resistance of the load equal to that of the generator. However, under this condition the power transfer efficiency is only 50%, which means that half the power generated is wasted as heat and Lorentz force or back emf inside the generator. For this reason, practical generators are not usually designed to operate at maximum power output, but at a lower power output where efficiency is greater. In electrical engineering, the maximum power (transfer) theorem states that, to obtain maximum power from a source with a fixed internal resistance, the resistance of the load must be made the same as that of the source. ...

## Vehicle-mounted generators

Early motor vehicles tended to use DC generators with electromechanical regulators. These were not particularly reliable or efficient and have now been replaced by alternators with built-in rectifier circuits. These power the electrical systems on the vehicle and recharge the battery after starting. Rated output will typically be in the range 50-100 A at 12 V, depending on the designed electrical load within the vehicle - some cars now have electrically-powered steering assistance and air conditioning, which places a high load on the electrical system. Commercial vehicles are more likely to use 24 V to give sufficient power at the starter motor to turn over a large diesel engine without the requirement for unreasonably thick cabling. Vehicle alternators do not use permanent magnets and are typically only 50-60% efficient over a wide speed range. Motorcycle alternators often use permanent magnet stators made with rare earth magnets, since they can be made smaller and lighter than other types. See also hybrid vehicle. Early 20th century Alternator made in Budapest, Hungary, in the power generating hall of a hydroelectric station. ... Power steering is a system for reducing the steering effort on cars by using an external power source to assist in turning the wheels. ... Note: in the broadest sense, air conditioning can refer to any form of heating, ventilation, and air-conditioning. ... In 1903, the first U.S. patent for an automobile electric self-starter was issued to Clyde J. Coleman of New York City (No. ... A diesel engine built by MAN AG in 1906 Rudolf Diesels 1893 patent on his engine design A Diesel engine is an internal combustion engine which operates using the Diesel cycle. ... The stator is the fixed part of a rotating machine. ... Rare earth ore Rare earth elements and rare earth metals are trivial names sometimes applied to a collection of 17 chemical elements in the periodic table, namely scandium, yttrium, and the lanthanides. ... For other types of Hybrid Transportation, see Hybrid (disambiguation)#Transportation. ...

Some of the smallest generators commonly found power bicycle lights. These tend to be 0.5 ampere, permanent-magnet alternators supplying 3-6 W at 6 V or 12 V. Being powered by the rider, efficiency is at a premium, so these may incorporate rare-earth magnets and are designed and manufactured with great precision. Nevertheless, the maximum efficiency is only around 60% for the best of these generators - 40% is more typical - due to the use of permanent magnets. A battery would be required in order to use a controllable electromagnetic field instead, and this is unacceptable due to its weight and bulk. Bicycle lighting has two purposes: seeing and being seen. ... Ferrofluid on glass, with a rare-earth magnet underneath. ...

Sailing yachts may use a water or wind powered generator to trickle-charge the batteries. A small propeller, wind turbine or impeller is connected to a low-power alternator and rectifier to supply currents of up to 12 A at typical cruising speeds. For other uses, see Propeller (disambiguation). ... This article is about the machine for converting the kinetic energy in the wind into mechanical energy. ... An impeller is a rotor inside a tube or conduit to increase the pressure and flow of a fluid. ...

## Engine-generator

Portable generator side view showing gasoline engine.
Engine - generator for a radio station (Dubendorf museum of the military aviation). The generator worked only when sending the radio signal (the receiver could operate on the battery power)
Hand-driven electric generator for a radio station (Dubendorf museum of the military aviation)

In addition to the engine and generator, engine-generators generally include a fuel tank, an engine speed regulator and a generator voltage regulator. Many units are equipped with a battery and electric starter. Standby power generating units often include an automatic starting system and a transfer switch to disconnect the load from the utility power source and connect it to the generator. Josephson junction array chip developed by NIST as a standard volt. ... Transfer switches allow switching from a primary power source to a secondary or tertiary power source and are employed in some electrical power distribution systems. ...

Engine-generators are often used to supply electrical power in places where utility power is not available and in situations where power is needed only temporarily. Small generators are sometimes used to supply power tools at construction sites. Trailer-mounted generators supply power for temporary installations of lighting, sound ampliification systems, amusement rides etc.

Standby power generators are permanently installed and kept ready to supply power to critical loads during temporary interruptions of the utility power supply. Hospitals, communications service installations, sewage pumping stations and many other important facilities are equipped with standby power generators. In telecommunication, the term standby has the following meanings: In computer and communications systems operations, pertaining to a power-saving condition or status of operation of equipment that is ready for use but not in use. ...

Small and medium generators are especially popular in third world countries to supplement grid power, which is often unreliable. Trailer-mounted generators can be towed to disaster areas where grid power has been temporarily disrupted.

The generator can also be driven by the human muscle power (for instance, in the field radio station equipment).

The generator voltage (volts), frequency (Hz) and power (watts) ratings are selected to suit the load that will be connected. Josephson junction array chip developed by NIST as a standard volt. ... For other uses, see Frequency (disambiguation). ... For delivered electrical power, see Electrical power industry. ...

Engine-generators are available in a wide range of power ratings. These include small, hand-portable units that can supply several hundred watts of power, hand-cart mounted units, as pictured above, that can supply several thousand watts and stationary or trailer-mounted units that can supply over a million watts. The smaller units tend to use gasoline (petrol) as a fuel, and the larger ones have various fuel types, including diesel, natural gas and propane (liquid or gas). A cart is a vehicle or device, using two wheels and normally one horse, designed for transport. ... Stationary can mean: Look up stationary in Wiktionary, the free dictionary. ... Utility trailer A Trailer is generally an unpowered vehicle pulled by a powered vehicle. ...

There are only a few portable three-phase generator models available in the US. Most of the portable units available are single phase power only and most of the three-phase generators manufactured are large industrial type generators. Portable communications devices refer to hand-held or wearable devices. ...

Portable engine-generators may require an external power conditioner to safely operate some types of electronic equipment. A power conditioner (also known as a line conditioner) is an electronic device, commonly taking the form of a powerstrip, that smooths out the peaks and dips of common household AC power. ...

### Human powered electrical generators

Human powered direct current generators are commercially available, and have been the project of some homebrew enthusiasts. Typically operated by means of pedal power, a converted bicycle trainer, or a foot pump, such generators can be practically used to charge batteries as large as 12 volts, and in some cases are designed with an integral inverter. Homebrew is an album by Paul Lansky. ...

A preferred hand-held generator is one that has an inverter. They are the smallest, quietest, and most fuel-efficient generators. Small portable generators have a standard A.C. alternator and run at a faster R.P.M. to generate power. Inverter models can run at slower RPMs to generate the power that is necessary, thus reducing the noise of the engine and making it more fuel-efficient. Inverter generators are best to power sensitive electronic devices such as computers and lights that use a ballast. The power output of a true sine wave inverter is more stable and is equal to or better than household electrical power. Regular generators that do not have AVR (Automatic Voltage Regulation) or which use low cost non-sine or modified sine wave inverters can damage electronics such as computers and sound systems due to their varying voltage. An inverter may be: inverter (electrical), which converts direct current (DC) to alternating current (AC) inverter (logic gate), also called a NOT gate. ...

### Mid-size stationary engine-generator

Side view of a large Perkins diesel generator, manufactured by F&G Wilson Engineering Ltd. This is a 100 kVA set.

The mid-size stationary engine-generator pictured here is a 100 kVA set which produces 415 V at around 110 A per phase. It is powered by a 6.7 litre turbocharged Perkins Phaser 1000 Series engine, and consumes approximately 27 litres of fuel an hour, on a 400 litre tank. Diesel engines in the UK run on red diesel and rotate at 1500 rpm. This produces power at a frequency of 50 Hz, which is the frequency used in the UK. In areas where the power frequency is 60 Hz (United States), generators rotate at 1800 rpm or another divisor of 3600. Diesel engine-generator sets operated at their peak efficiency point can produce between 3 and 4 kilowatthours of electrical energy for each litre of diesel fuel consumed, with lower efficiency at part load. Image File history File linksMetadata No higher resolution available. ... Image File history File linksMetadata No higher resolution available. ... In the United States the term (Volt-amps) in Electrical terms, means watts. ... In the United States the term (Volt-amps) in Electrical terms, means watts. ... Josephson junction array chip developed by NIST as a standard volt. ... For other uses, see Ampere (disambiguation). ... Three phase systems have 3 waveforms (usually carrying power) that are 2/3&#960; radians (120 degrees,1/3 of a cycle) offset in time. ... Turbocharger Cut-away A turbocharger is a device used in internal-combustion engines to increase the power output of the engine by increasing the mass of oxygen and fuel entering the engine. ... Diesel is a product used as a fuel in a diesel engine invented by Rudolf Diesel, and perfected by Charles F. Kettering. ...

## Patents

• U.S. Patent 222,881  -- Magneto-Electric Machines : Thomas Edison's main continuous current dynamo. The device's nickname was the "long-legged Mary-Ann". This device has large bipolar magnets. It is inefficient.
• U.S. Patent 373,584  -- Dynamo-Electric Machine : Edison's improved dynamo which includes an extra coil and utilizes a field of force.
• U.S. Patent 359,748  -- Dynamo Electric Machine - Nikola Tesla's construction of the alternating current induction motor / generator.
• U.S. Patent 406,968  -- Dynamo Electric Machine - Tesla's "Unipolar" machine (i.e., a disk or cylindrical conductor is mounted in between magnetic poles adapted to produce a uniform magnetic field).
• U.S. Patent 417,794  -- Armature for Electric Machines -Tesla's construction principles of the armature for electrical generators and motors. (Related to patents numbers US327797, US292077, and GB9013.)
• U.S. Patent 447,920  -- Method of Operating Arc-Lamps - Tesla's alternating current generator of high frequency alternations (or pulsations) above the auditory level.
• U.S. Patent 447,921  -- Alternating Electric Current Generator - Tesla's generator that produces alternations of 15000 per second or more.

â€œEdisonâ€ redirects here. ... Direct current (DC or continuous current) is the continuous flow of electricity through a conductor such as a wire from high to low potential. ... Nikola Tesla (1856-1943)[1] was a world-renowned Serbian inventor, physicist, mechanical engineer and electrical engineer. ... City lights viewed in a motion blurred exposure. ... Induction Motor (IM) is one kind of AC motor where power is supplied to the rotating device by induction. ...

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