DC GENERATOR CONSTRUCTIONDC GeneratorsES-05Page 16Rev. 0Figure 12 Compounded DC GeneratorCompoundGeneratorsSeries-wound and shunt-woundgenerators have a disadvantage inthat changes in load current causechanges in generator output voltage.Many applications in whichgenerators are used require a morestable output voltage than can besupplied by a series-wound or shunt-wound generator. One means ofsupplying a stable output voltage isby using a compound generator.The compound generator has a fieldwinding in parallel with thegenerator armature (the same as ashunt-wound generator) and a fieldwinding in series with the generator armature (the same as a series-wound generator) (Figure 12).The two windings of the compounded generator are made such that their magnetic fields will eitheraid or oppose one another.If the two fields are wound so that their flux fields oppose one another, the generator is said to bedifferentially-compounded. Due to the nature of this type of generator, it is used only in specialcases and will not be discussed further in this text.If the two fields of a compound generator are wound so that their magnetic fields aid one another,the generator is said to be cumulatively-compounded. As the load current increases, the currentthrough the series field winding increases, increasing the overall magnetic field strength andcausing an increase in the output voltage of the generator. With proper design, the increase inthe magnetic field strength of the series winding will compensate for the decrease in shunt fieldstrength. Therefore, the overall strength of the combined magnetic fields remains almostunchanged, so the output voltage will remain constant. In reality, the two fields cannot be madeso that their magnetic field strengths compensate for each other completely. There will be somechange in output voltage from the no-load to full-load conditions.
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