Voltage Build-Up of a Shunt Generator
Voltage Build-Up of a Shunt Generator Before loading a shunt generator, it is allowed to build up its voltage. Usually, there is always present some residual magnetism in the poles, hence a small e.m.f. is produced initially. This e.m.f. circulates a small current in the field circuit which increases the pole flux (provided field circuit is properly connected to armature, otherwise this current may wipe off the residual magnetism). When flux is increased, generated e.m.f. is increased which further increases the flux and so on. As shown in Fig. 3, Oa is the induced e.m.f. due to residual magnetism which appears across the field circuit and causes a field current Ob to flow. These current aids residual flux and hence produces, a larger induced e.m.f. Oc. In turn, this increased e.m.f. Oc causes an even larger current Od which creates more flux for a still larger e.m.f. and so on. Now, the generated e.m.f. in the armature has (a) to supply the ohmic drop 𝑖𝑓𝑅𝑓 in the winding...