What are the benefits of using a permanent magnets for field excitation on a generator/turbine?
916842
I have a small wind turbine which uses permanent magnets instead of a field coil.  The main benefit I can see is in keeping the electronics on the ground.  As the wind speed increases, the output voltage (and power) from the generator will increase as well.  I have a shunt regulator at the batteries to prevent overcharging.  Everything outside on the tower is very simple and less likely to break.  Other than mechanical breakdown, repairs to the system can usually be made on the ground level.\n\nOn a gasoline powered generator, sometimes permanent magnets are turned inside the AC output coils.  This eliminates the need for brushes and the voltage regulator board.  AC output coils have been designed to supply 120VAC at 3600RPM.  If the engine speed changes, the output voltage will change as well.  Output voltage will also change with load variations.\n\nI have more generator information online.\nhttp://members.rennlist.org/warren/genfaq.html\nhttp://members.rennlist.org/warren/generator.html
755807
In order to know how 3-phases of voltage (separated by 120 degrees) are produced, one would have to know how a 3-phase generator works and know a bit about electromagnetic theory.\n\nIn nearly all power plants (except for some wind turbines), a 3-phase synchronous generator is used.  This type of generator has one or more wire coils attached to the shaft (the rotor) and a set of coils evenly spaced around the frame surrounding the shaft (this area is known as the stator).\n\nThe coils on the rotor are energized by a small DC source and become constant electromagnets with north/south poles determined by the direction in which the current flows.  The shaft is moved by a source of mechanical power.  Generally a steam turbine is used where the steam is heated from some source of energy like coal, natural gas, nuclear etc.\n\nSo as you can imagine, we have one or more electrogmagnets attached to a shaft being rotated by a turbine.  Remember that these rotating electromagnets are inside the evenly spaced windings on the stator.  Faraday's law states that a time-changing magnetic flux in a coil will produce a voltage in that coil.  Since the rotor electromagnets are constantly changing position relative to the stator coils, the magnetic flux seen by the stator coils is also constantly changing.  The wire coils on the stator frame are evenly spaced such that the induced voltage waveforms will be spaced 120 degrees apart.\n\nSo, we then have sinusoidal voltage waveforms produced on the stator coils such that they are 120 degrees apart.  These coils on the stator are then connected in either wye or delta configurations and carefully hooked up to the power grid.\n\nSo that is a somewhat simplified view of what is happening.  There are various other complications that I have not mentioned, but are not important in getting the general idea.  You might be able to find a nice 3-phase electric generator animation on howstuffworks.com or Wikipedia.
616514
Generating static electricity.
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An electric generator is a device used to convert mechanical energy into electrical energy.\n\nThe generator is based on the principle of "electromagnetic induction" discovered in 1831 by Michael Faraday, a British scientist. Faraday discovered that if an electric conductor, like a copper wire, is moved through a magnetic field, electric current will flow (be induced) in the conductor. So the mechanical energy of the moving wire is converted into the electric energy of the current that flows in the wire.The mechanical energy needed to turn the generator comes from the brown hand crank at the front of the generator. In a hydroelectric power plant, the mechanical energy to turn the generator comes from the water turbine, which is turned by the force of falling water. The hand crank causes the red wire to spin inside a magnetic field (the blue lines). As Faraday learned, moving the wire through the magnetic field causes electric current to flow in the wire. The turning red wire is connected to a volt meter, which shows the amount of electric current that is produced. In a hydroelectric plant, the generator is connected to transmission lines that deliver the electricity to your home or business.\n\nThe controls allow you to control the speed and direction of the generator and turn portions on and off for greater clarity. You can also use the radio buttons to show a direct current, or DC generator (with commutator) or an alternating current, or AC generator (without commutator).
1054406
And just how do you propose I put a diagram on Y!A?\n\nNonetheless, electricity can be used to generate electricity, as mentioned.  Put three magnets around a rotating shaft & you get 3Φ electricity.\n\nMagnets work in compasses to help a person find direction.\n\nMagnets can be used to hold cabinet doors closed.\n\nMagnets can be used to lift things (like in a junkyard to move vehicles to a compactor), or to remotely move magnetic items (like if you can't reach your car keys, you could retrieve them with a strong enough magnet).
154800
From what I know about permanent magnets, the heat is the killer when you get near the transistion temperature of the material.  When you do this, the magnetic domains become randomly aligned again and the pole force gets reduced.  If you keep heating it, you can totally demagnatize the material.  In fact, during the manufacturing process, the material is heated very hot under a very strong magnetic field and cooled, allowing the aligned domains to be "frozen" making a high force pole.  \n\nSo in motor design, the aerodynamics of the rotor, the eddy currents generated while running, and the torque loads, will all contribute to heating the magnets.  If you can master the thermal design, you can make very powerful motors.
905984
Not just any A/C motor will.\n\nCurrent is generated by ,,"Waving a MAGNET past a COIL"\n\nUsing a NON-Magnet produces nothing.\n\nMost A/C motors do not have permanent magnets.\n\nA/C Motor's "magnetism" is typically created by the Supply Current---Electromagnetism\n\nA/C motors can be converted to generate,,but it's not so simple as just spinning the shaft of a DC motor or any permanent magnet motor.\n\nThere's stuff all over the net which explains what type A/C motor is easiest/best to convert,,and what's required.\n\nhttp://users.aber.ac.uk/iri/WIND/TECH/MISC/MotorsAsGenerators.html\n\nhttp://www.otherpower.com/otherpower_wind_alternators.html
1005187
At its simplest, a generator involves a spinning object inside a coil, and produces electricity.  It's tempting to think that if there were no friction, that the spinning object would turn forever always generating electricity, but that's not the case.\n\nWhen energy is extracted from the generator, it is because the generator is producing a current in its coil.  This current in the coil creates a magnetic field that actually slows down the spinning object.  Friction isn't the only force slowing down the system, it's not even an important force.  The important force is this electromagnetic braking force which arises as a direct and unavoidable consequence of the extraction of energy from the generator.
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MAGNET THATS POWERED BY ELECTRICITY
202402
A long straight coil of wire can be used to generate a nearly uniform magnetic field similar to that of a bar magnet. Such coils, called solenoids, have an enormous number of practical applications. The field can be greatly strengthened by the addition of an iron core. Such cores are typical in electromagnets. \n\nSolenoid Field from Ampere's Law:-\n\nTaking a rectangular path about which to evaluate Ampere's Law such that the length of the side parallel to the solenoid field is L gives a contribution BL inside the coil. The field is essentially perpendicular to the sides of the path, giving negligible contribution. If the end is taken so far from the coil that the field is negligible, then the length inside the coil is the dominant contribution.
1185123
The only motionless electromagnetic generator I know of is a solar panel.  While you can generate energy with coils you need a strong changing magnetic field.   The only way I know how to make one  without a preexisting current is spinning some kind of a magnet by wind, water or steam.\n\nNo something does not have to work to get a patent.  It is not the patent offices job to make sure something works.\nA patent is only good if you can successfully sue someone for infringing on it.\nI can patent an teleportation device right now if I want too but unless builds one almost exactly like the one I describe I am just wasting my time and money.
958598
Here are a few ideas on reducing generator noise, taken from my generator web site.\nhttp://members.rennlist.org/warren/generator.html\n\nChoose an operating location as far away as possible. Note that a larger gauge wire is needed to reduce voltage drop as line length increases. Reducing line loss is required to minimize power loss and to ensure maximum power is available to the house. Lights will flicker less when heavy loads are attached. \n\nChange the exhaust system. Noise from the portable generator systems comes primarily from two sources, the engine block and the exhaust system. With an air cooled engine there is little you can do about block noise. Some engines can have a larger muffler attached or make other changes to the exhaust system. Merely mounting exhaust pipe vertically will noticeably reduce noise. \n\nBuild a noise shielding enclosure. This could be as simple as a piece of plywood to reflect sound away from the house to a separate shed to hold the generator. Design your enclosure with safety in mind. Provide adequate air circulation and ventilation to prevent heat buildup and to remove carbon monoxide. \n\nIf the noise bothers your neighbors, invite them over for coffee or offer to run line to their home to power the freezer or a few lights. Talk to them before starting the engine, ask they let you know if the noise is bothersome before they phone the police or harbor any resentment. A little diplomacy can go a long way. \n\nLast resort, shut off the engine or buy a quiet generator.
335160
great question. but u can witness these type in powerplants only. tat to it will be a.c. and not d.c. these have a prime mover of steam turbine. it will be largest ever found and if it d.c. it will have lots of losses and usually they produce a.c. go to the powerplants and visit the generators. u can use the formula n=(120f/p) where n is the rpm and p is the no.of poles and f is the frequency. they may have salient pole type rotor. i don know the dimensions. but the conductors are not cooled by air but with nitrogen..
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a generator is technology based on the scientific phenomenon that is today known as faraday's law.    \n\nif you have a loop of wire and you stick it into a magnetic field, well, then you'll have a loop in a magnetic field.  no big deal.  but if you then do something that changes the magnetic field somehow - either by changing the strength of the field, or its orientation relative to the loop - then if you are paying attention to such things you will notice that there is suddenly a current flowing in the wire.  and when you stop moving the field around, the current stops flowing.  faraday's law is a mathematical statement of this observed natural phenomenon, which is called induction.\n\nanyway, a generator is a thing that uses induction to convert mechanical energy to electrical energy.  it is basically what i just said - some big permanent magnets arranged such that there is a region of space with a strong magnetic field between them - and some big coil of wire in the middle.  \n\nthis coil is attached to a rod which leads out of the device and to a handle, or gears, or engine or turbine, or basically some -thing- that makes it spin.  the mechanical energy of the spinning is then converted into electrical energy, which drives the current in the loop, and powers whatever electrical device the two ends of the loop are attached to!\n\nand, basically that's it.  because the coil goes around and around, the current flows back and forth in a sine-wave pattern, and that's why generators are used for making alternating current, which is what is in the power grid and the walls of your house.\n\nnote that an electric motor is essentially a generator that operates in reverse - you connect some driving AC voltage to the coils, and the changing current causes a magnetic field to form which opposes that of the permanent magnets, so (as anyone who has ever played with magnets will tell you) there is a considerably strong force that pushes the coil away from the magnet.  with proper design you can make it keep pushing itself all the way around a circle, and voila, you have a motor.
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go 4 d c motor ,,,, model of it is easy n interesting, eye catcher.... i made that last yr n got highest marks... :-)... it ll include both elec n magnetics..
91676
I answered your question already.  Magnetic field strength is governed by amount of current flow.
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Electricity and magnetism are closely related.  When a current goes through a wire, it creates a magnetic field around the wire.  Similarly, if a magnetic field is moved past a wire, it can induce a current.\n\nA generator spins a magnet past a series of coiled wires, inducing currents in them.  Generators and alternators both work in this way.  The difference between the two is that in a generator, the current always goes in the same direction, while in an alternator, it switches directions due to the fact that the polarity of the magnet changes as it rotates.\n\nGenerators always produce Direct Current (DC current), while alternators always produce Alternating Current (AC current).\n\nThe difference in nuclear, steam, coal, oil and hydroelectric powerplants is simply in how the rotation of the generator is produced.  The generators work in exactly the same way in each case.\n\nSolar power is different.  In the case of solar power, the current can be generated in one of several different ways.  These are more complicated, however, and I don't know the specifics of how they work.  Sorry.