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Thread: Magnetic Field of an electric generator.

  1. #1 Magnetic Field of an electric generator. 
    Forum Freshman Dani's Avatar
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    In order to produce an electric current in an electric generator you must have first a magnetic field. So basically (wikipedia):
    -The EMF generated is proportional to the rate of change of the magnetic flux-
    So, my doubt is how these magnetic fields are first generated for instance in the electric generators of a dam and what order of magnitude are they typically?

    Thank you very much for your answers.


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  3. #2  
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    The rotating magnetic field is produced by a coil on the rotor of the generator. The direct current which supplies the magnetizing current in this coil comes from another machine called an exciter.

    http://www.whitbyhydro.on.ca/pdf/5.2.C_GenBasics.pdf


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    Forum Freshman Dani's Avatar
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    Hi Harold, thanks for your answer. But then, how does the exciter generates the current that drives the magnetizing coil in the first place?
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    The exciter can use permanent magnets to generate its required magnetic flux.

    Another way to get the excitation current is to use the rectified output of the a-c generator. To get the initial excitation current you would use a battery to "flash the field" of the generator, then the battery can be disconnected once the generator is creating its own field current.
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  6. #5  
    Forum Freshman Dani's Avatar
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    ahh, that pretty much answers my question, thanks again Harold.
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