Download as DOC, PDF, TXT or read online from Scribd Modinagar has prepared this Physics project ac generator In accordance with guide lines This is certify that sakar singhal of class XII-D 'Science of Dayawati modi public school . In order to make the most practical AC generator (or alternator, as it is also known ), which design makes How fast must a pole alternator spin in order to produce 60 Hz AC power? . front of the class, for those who have not seen it. A.C. Generator, Physics Project Report A.C. Generator, AC Generator, Electric Generator, Principle of A.C. Generator, Construction of Generator, Working of A.C.
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The armature is contained within the windings of the stator and is connected to the output. Clipping is a handy way to collect important slides you want to go back to later. Two brushes are spring-held in contact with the slip rings to provide the continuous connection between the field coil and the external excitation circuit. Independently of Faraday, the Hungarian Anyos Jedlik started experimenting in with the electromagnetic rotating devices which he called electromagnetic self-rotors. Tachogenerators are frequently used to power tachometers to measure the speeds of electric motors, engines, and the equipment they power.
According to Faradays laws of electromagnetic induction, whenever a conductor is placed in a varying magnetic field OR a conductor is moved in a magnetic field , an emf electromotive force gets induced in the conductor. The magnitude of induced emf can be calculated from the emf equation of dc generator.
If the conductor is provided with the closed path, the induced current will circulate within the path. In a DC generator, field coils produce an electromagnetic field and the armature conductors are rotated into the field. Thus, an electromagnetically induced emf is generated in the armature conductors.
The direction of induced current is given by Flemings right hand rule. According to Flemings right hand rule, the direction of induced current changes whenever the direction of motion of the conductor changes. Lets consider an armature rotating clockwise and. When the armature completes a half rotation, the direction of motion of that particular conductor will be reversed to downward.
Hence, the direction of current in every armature conductor will be alternating. If you look at the above figure, you will know how the direction of the induced current is alternating in an armature conductor. But with a split ring commutator, connections of the armature conductors also gets reversed when the current reversal occurs. And therefore, we get unidirectional current at the terminals. DC generators can be classified in two main categories, viz; i Separately excited and ii Selfexcited.
In this type, field coils are energized from an independent external DC source. In this type, field coils are energized from the current produced by the generator itself. Initial emf generation is due to residual magnetism in field poles. The generated emf causes a part of current to flow in the field coils, thus strengthening the field flux and thereby increasing emf generation. Self excited dc generators can further be divided into three types a Series wound - field winding in series with armature winding b Shunt wound - field winding in parallel with armature winding c Compound wound - combination of series and shunt winding.
Some AC motors may be used as generators, turning mechanical energy into electric current. Induction generators operate by mechanically turning their rotor faster than the synchronous speed, giving negative 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 reducing 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 leading voltage; this is usually done by connection to an electrical grid, or sometimes they are self-excited by using phase correcting capacitors.
The working principle of an alternator or AC generator is similar to the basic working principle of a DC generator. Above figure helps you understanding how an alternator or AC generator works. According to the Faraday's law of electromagnetic induction, whenever a conductor moves in a magnetic field EMF gets induced across the conductor. If the close path is provided to the conductor, induced emf causes current to flow in the circuit.
Now, see the above figure. Let the conductor coil ABCD is placed in a magnetic field. The direction of magnetic flux will be form N pole to S pole. The coil is connected to slip rings, and the load is connected through brushes resting on the slip rings.
Now, consider the case 1 from above figure. The coil is rotating clockwise, in this case the direction of induced current can be given by Fleming's right hand rule, and it will be along A-BC-D.
As the coil is rotating clockwise, after half of the time period, the position of the coil will be as in second case of above figure. In this case, the direction of the induced current according to Fleming's right hand rulewill be along D-C-B-A.
It shows that, the direction of the current changes after half of the time period, that means we get an alternating current. Main parts of the alternator, obviously, consists of stator and rotor.
But, the unlike other machines, in most of the alternators, field exciters are rotating and the armature coil is stationary. Unlike in DC machine stator of an alternator is not meant to serve path for magnetic flux.
Instead, the stator is used for holding armature winding. The stator core is made up of lamination of steel alloys or magnetic iron, to minimize the eddy current losses. At high voltages, it easier to insulate stationary armature winding, which may be as high as 30 kV or more.
The high voltage output can be directly taken out from the stationary armature. Whereas, for a rotary armature, there will be large brush contact drop at higher voltages, also the sparking at the brush surface will occur. The armature winding can be braced well, so as to prevent deformation caused by the high centrifugal force.
Salient pole type: Salient pole type rotor is used in low and medium speed alternators. Construction of AC generator of salient pole type rotor is shown in the figure above. This type of rotor consists of large number of projected poles called salient poles , bolted on a magnetic wheel.
These poles are also laminated to minimize the eddy current losses. Alternators featuring this type of rotor are large in diameters and short in axial length. Cylindrical type: Cylindrical type rotors are used in high speed alternators, especially in turbo alternators.
This type of rotor consists of a smooth and solid steel cylinder havingg slots along its outer periphery. Field windings are placed in these slots. The DC suppy is given to the rotor winding through the slip rings and and brushes arrangement.
Linear electric generator In the simplest form of linear electric generator, a sliding magnet moves back and forth through a solenoid - a spool of copper wire. An alternating current is induced in the 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. Variable speed constant frequency generators Many renewable energy efforts attempt to harvest natural sources of mechanical energy wind, tides, etc. Because these sources fluctuate in power applied, standard generators using permanent magnets and fixed windings would deliver unregulated voltage and frequency.
The overhead of regulation whether before the generator via gear reduction or after generation by electrical means is high in proportion to the naturally-derived energy available. New generator designs such as the asynchronous or induction singly-fed generator, the doubly fed generator, or the brushless wound-rotor doubly fed generator are seeing success in variable speed constant frequency applications, such as wind turbines or other renewable energy technologies.
These systems thus offer cost, reliability and efficiency benefits in certain use cases. Common use cases Vehicular generators Roadway vehicles. Motor vehicles require electrical energy to power their instrumentation, keep the engine itself operating, and recharge their batteries.
Until about the s motor vehicles tended to use DC generators 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 Bicycles require energy to power running lights and other equipment. There are two common kinds of generator in use on bicycles: In reality, neither of these is a dynamo, properly speaking - they are small permanent-magnet alternators. Sailboats Sailing boats 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 generator to supply currents at typical wind or cruising speeds.
An engine-generator 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. The primary advantage of engine-generators is the ability to independently supply electricity, allowing the units to serve as backup power solutions.
Human powered electrical generators. A generator can also be driven by human muscle power for instance, in field radio station equipment. Protesters at Occupy Wall Streetusing bicycles connected to a motor and one-way diode to charge batteries for their electronics Human powered direct current 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 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. At the end of which an undetermined period of rest and recovery will be required.
At Watts the average "healthy human" becomes exhausted within 10 minutes. It is important to note that the power figures referenced above are for direct human output and not the electrical power that can be generated from it. 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 the Air , medical and other needs in remote stations and towns.
Mechanical measurement Designed to measure shaft speed, a tachogenerator is a device which produces an output voltage proportional to that speed.
Tachogenerators are frequently used to power tachometers to measure the speeds of electric motors, engines, and the equipment they power. With precise construction and design, generators can be built to produce very precise voltages for certain ranges of shaft speeds. Equivalent circuit. Equivalent circuit of generator and load. The generator is represented by an abstract generator consisting of an ideal voltage source and an internal resistance.
The generator's and parameters can be determined by measuring the winding resistance corrected to operating temperature , and measuring 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.
Flag for inappropriate content. Related titles. Jump to Page. Search inside document. Acknowledgement Acknowledgement is the most beautiful page in any project s file page.
For electrostatic generators like the Van de Graff machine, U. Terminology Dynamos generate direct current, usually with voltage or current fluctuations, usually through the use of a commutator Alternators generate alternating current, which may be rectified by another external or directly incorporated system. Mechanically a generator consists of a rotating part and a stationary part Rotor: The rotating part of an electrical machine Stator: The stationary part of an electrical machine, which surrounds the rotor Electrically, generators contain two sets of wire windings Armature: Faraday disk generator The Faraday disk was the first electric generator.
Direct current generators This large belt-driven high-current dynamoproduced amperes at 7 volts. Alternating Current Generator Ferranti alternating current generator, c. Need of a Split ring commutator: Self excited dc generators can further be divided into three types a Series wound - field winding in series with armature winding b Shunt wound - field winding in parallel with armature winding c Compound wound - combination of series and shunt winding Alternating current Generator Induction generator Some AC motors may be used as generators, turning mechanical energy into electric current.
Field exciter winding is placed in rotor, and the low dc voltage can be transferred safely. Connecting an alternator in grid is called as synchronization of alternator Linear electric generator In the simplest form of linear electric generator, a sliding magnet moves back and forth through a solenoid - a spool of copper wire. Common use cases Vehicular generators Roadway vehicles Motor vehicles require electrical energy to power their instrumentation, keep the engine itself operating, and recharge their batteries.
Genset An engine-generator is the combination of an electrical generator and an engine prime mover mounted together to form a single piece of self-contained equipment. Human powered electrical generators A generator can also be driven by human muscle power for instance, in field radio station equipment.
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Anonymous U4YeY3t3U. Shubham Birange. Srinivas Kamapantula. Kaiba Seto. Sambasivarao Karlakunta. Zaid Al-Ali. All of our household appliances runs on ac current. Differentiate w. It make angle q with vertical. Let position of the coil at any time t. If w is uniform angular speed of the coil. Flag for inappropriate content. Related titles. Jump to Page. Search inside document. Murat Canbaz. Kamlesh Motghare. Rigoberto Urrutia. Guillermo Leon Uribe Jimenez.
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