For every generator which is used as a self excited generator there must exist some residual magnetic flux. When armature rotates, conductors cut this small residual flux to produce the e.m.f. Er. This e.m.f. drives small current through field winding. Thus field current If now produces more flux which is greater than residual flux. Hence more e.m.f. gets induced. This further drives more current through field to produce more flux.which is greater than residual flux. Hence more e.m.f. gets induced. This further drives more current through field to produce more flux. This process is cumulative and continues till rated voltage gets build up. This is shown in the Fig. 1.
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| Fig. 1 Voltage building in self excited generator |
1.1 Causes of Failure to Excite Self Excited Generators
The causes of failure, the method of detection and the corresponding remedy are given in table 1.
