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DC Generator Animation





DC machine is generally an alternating current machine in which the current vary sinusoidally and is furnished with a special device named commutator. 
The commutation is the process by which the AC is converted into DC. 
The commutation process also helps in keeping the armature field stationary in space.
The DC generator is the device which helps in converting the mechanical energy into electrical energy. 

It is based on the principal that when the conductor is rotated in a magnetic field and amount of induced voltage is generated in the conductor. DC generators are used only for special applications and localised DC power generator.

Construction of DC Generator:
A DC generator mainly consists of four main parts: (a) field windings (b) armature (c) commutator (d) brushes

Field Windings:
The magnetic field windings or system is stationary part of the DC generator. 
The main prpose of the field system is to produce a uniform magnetic field in the air gap, within which the armature rotates. 
Electromagnets are used and preferred in comparison to with permanent magnet due to its greater magnetic effect. 

Armature
The armature is the rotating part of the DC generator, the generator of the DC generator cosists of a shaft ipon which a laminated cyclindrical core is mounted called armature core. 
The armature core has slots in its outer surface. The laminations are insulated from each other and tightly clamped together. 
The armature is the one of the very important requirement of DC generator without the whole operation would fail. 
The connected arrangement of slots and conductor is better known as armature winding.

Commutator:
The commutator is one of very important part of DC machine which rotates with the armature; the main function of commutator is to convert DC to AC which also keeps the magnetic flux stationary. 
As alternating voltage is produced in the coil, which is rotating in a magnetic field but direct is required in the external circuit and for this purpose we need a commutator.  
The commutator receives the current from brushes which are placed in the rotating armature as well.

Brushes
Carbon brushes are used in DC generators and are generally needed to collect from the armature winding. 
Two or more brushes are used in commutator for uniform current distribution. 
Each brush is supported in metal box called brush box. 
The current so produced in the armature is then passed to the external circuit with the help of these brushes.

Excitation of DC Machine
In DC generator the field coils is excited in order to produce the magnetic flux.
The production of the useful magnetic flux with the application of electric current to the field windings is better termed as excitation.
 

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From Yahoo Answers

Question:Any information to help me for example links and resources for usefull information for the questions. thanks biggest help 10 points!!! questions for referencing, 1.Describe the characteristics and principles of operation of a DC electromagnetic generator. You should discuss the use commutators and brush gear and illustrate your answer with sketches or other graphic images. 2.Describe the characteristics and principles of operation of an AC electromagnetic generator. For example, you should discuss the relative motion between conductors and magnetic fields, production and regulation of AC using field/ slip-ring control. Give examples of how the basic principles of AC generation are used in electrical power generating systems.

Answers:Hi again, Joe, I just updated my initial answer to your rv question. I suggest you rely more on careful search of google than this forum. We try to help, but really there is is usually more information on the net than we can give. However, check this excellent reference: http://www.animations.physics.unsw.edu.au/jw/electricmotors.html and then give google a try. e.g. http://www.google.com/search?hl=en&rls=com.microsoft%3Aen-US&q=ac+and+dc+generators&btnG=Search&aq=f&oq=&aqi=g-m3 .

Question:In my algebra/triganometry-based physics class (on electricity and magnetism) and yesterday our professor went over how to convert and AC generator into a DC generator; it got kind of confusing so i tried to read it over in our book but there's only like 3 senteceson it... could anyone help explain it to me in a simpler way? thanks. in response to the first reply... sorry, i meant how would you convert an ac generator into a dc one, not change it up entirely

Answers:Do you mean, convert AC into DC, which would use a diode bridge circuit, or take an actual AC generator and turn it into a DC generator? I can't think why anyone would want to do the latter. At the least is would mean swapping the slip rings for a commutator......that really would be confusing. Surely not. I think you need to repost and be a bit more explicit about what the problem is. :-)

Question:and why DC generator cannot be converted into an AC generator?please also explain why alternating voltage can travel long distance but DC cannot?

Answers:AC generators can be converted into DC generator by means of a RECTIFIER. DC generator can be converted into AC generator by means of an INVERTER, just it is more complicated. DC and AC can both travel long distances just it easier to work with AC than DC. In order to avoid losses in the transmission lines is better to have very high voltages in there, however we actually use low voltages in houses and industry so in order to have a efficient electrical system we need to be able to change from low voltage to high and back easily, this can be done for AC, easily, by means of a TRANSFORMER. To change the levels of voltage in DC is much more complicated and much less efficient (but it can be done), then it is much easier and much less costly to use AC and if we need DC we can easily get it from AC.

Question:* DC generators, slip rings, produce direct current * DC generators, commutators produce direct current * Ac generators, commutators produce alternating current * Ac generators, no commutators or slip rings are used YES, this is homework help. NO, this is not for a quiz. And if you do not know please do not post. Thanks.

Answers:Generators (AC or DC) can be manufactured to produce output from either the rotor or the stator. If from the stator, the output is AC and one or more diodes are needed if DC is wanted. If from the rotor, the current within the rotor is AC and can be (1) picked off with slip rings, providing AC, and converted to DC with diodes if needed, or (2) picked off with commutator and brushes if DC is needed. So one answer to the question would be, ...except that any DC generator must use commutator/brushes or diodes. I guess you have listed multiple-choice options. If so the only correct answer is #2.

From Youtube

generators DC and AC :Simple video about different between Dynamo (DC generator) and Alternator (AC generator). I think this animation can be useful for education of basic about electricity. YOU CAN DOWNLOAD AND SAVE THIS VIDEO FOR EDUCATIONAL OR OTHER NON-COMMERCIAL USE.

Dc Generator :Check us out at www.tutorvista.com Simple direct current (DC) generators contain an armature (or rotor), a commutator, brushes, and a field winding. The interactive tutorial presented below examines the operation of a simple DC or direct current generator. Translate the slider back and forth to adjust the frequency of the current. Note that the voltage amplitude increases with frequency. A variety of sources can supply mechanical energy to the DC generator to turn its armatures in order for its coils to cut through the lines of force in a magnetic field. These sources include steam, wind, a waterfall, or even an electric motor. In a direct current generator, the commutator's job is to change the alternating current (AC), which flows into its armature, into direct current. To put it another way, commutators keep the current flowing in one direction instead of back and forth. They accomplish this task by keeping the polarity of the brushes stationed on the outside of the generator positive. The commutator is made up of copper segments, with a pair (of segments) for every armature coil being insulated from all the others. The stationary brushes, which are graphite connectors on the generator, form contact with opposite parts of the commutator. As the armature coil turns, it cuts across the magnetic field, and current is induced. At the first half turn of the armature coil (clockwise direction), the contacts between communicator and brushes are reversed. The first brush now ...