DC GeneratorsDC GENERATOR CONSTRUCTIONRev. 0 Page 15ES-05Figure 10 Series-Wound DC GeneratorFigure 11 Output Voltage-vs-Load Current for Series-WoundDC GeneratorSeries-WoundDCGeneratorsWhen the field winding of a DCgenerator is connected in serieswith the armature, the generatoris called a series-woundgenerator (Figure 10).The excitation current in aseries-wound generator is thesame as the current thegenerator delivers to the load.If the load has a high resistanceand only draws a small amountof current, the excitationcurrent is also small. Therefore,the magnetic field of the seriesfield winding is weak, makingthe generated voltage low.Conversely, if the load draws a large current, the excitation current is also high. Therefore,the magnetic field of the series field winding is very strong, and the generated voltage is high.As you can see in Figure 11, in aseries generator, changes in loadcurrent drastically affect thegenerator output voltage. Aseries generator has poor voltageregulation, and, as a result, seriesgenerators are not used forfluctuating loads. As is the casefor the shunt-wound generator, aseries-wound generator alsoexhibits some losses due to theresistance of the windings andarmature reaction. These lossescause a lower terminal voltagethan that for an idealmagnetization curve.
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