The DC Generator

Discussion in 'Homework Help' started by J.ELKINS, Jun 8, 2008.

  1. J.ELKINS

    Thread Starter New Member

    Jun 8, 2008
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    I have been asked a question on DC generators for my assignment about motors and generators. I have become stuck as couldnt find great resources to help me answer the question. It is as follows.

    A shunt generator has a ‘drooping’ characteristic of output voltage verses load current, and the series generator has a ‘rising’ characteristic of output voltage verses load current. By combining the two characteristics an output voltage which changes very little with change in load current is achieved. By what name is this combination of characteristics known?
     
  2. Newton1Law

    Member

    Aug 22, 2007
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    The most common connection for DC generators combines both the shunt and series winding and is named a compound generator.
    Hope this helps.
     
  3. J.ELKINS

    Thread Starter New Member

    Jun 8, 2008
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    Yes thanks very much for your reply, i realise from my motors essay (and from work, im an apprentice elevator engineer on day release to college) that the compound wound is a series and shunt wound configuration. I think maybe that the question is worded badly as I dont think its asking for the winding configuration, it wants to know what charicteristic is produced from the output voltage to load current if the shunt wound has a drooping curve, and the series a rising curve, if you put them together then i agree you get a compound wind but is that what the question is asking? does it want me to produce the curve for a compound wound generator? what would this characteristic be known as if the shunts drooping and series rising? any ideas? thanks again
     
  4. Newton1Law

    Member

    Aug 22, 2007
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    Maybe this will help. The shunt wound generator has the field windings in placed in parallel with the output voltage terminals of the generator. Thus the current that is driven through the field windings (and by this current, the strength of the magnetic field produced) is subject to the output voltage of the generator. As the load supplied by the generator goes up, the resulting voltage drop in the armature windings increase and your output voltage goes down. As this voltage goes down, the field current also goes down since it is attached in parallel to the output terminals of the generator. This in turn decreases the magnetic field strength and further reduces the output of the generator.

    The series wound field generates its field current (and thus the resulting magnetic field) with the same current flow that is supplied to the load since the field winding is in series with the armature windings supplying the load. As the load increases, the field current also must increase and the magnetic field then will increase forcing the terminal voltage of the generator to increase. (All this within the operating parameters of the generator).

    Graphically the shunt generator output voltage vs. load current would look like line with a negative slope. The series wound generator curve would have a positive slope. These curves are not linear but the machine may be designed to maximize the outputs of both fields to produce a steady voltage output over a give range of load.
     
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