The typical value of SCR for modern alternator is around:
Correct answer: 1. 0.5
Short circuit ratio or SCR is defined as a measure of the stability of an electromechanical generator. Mathematically it is defined as the ratio of the field current required in order to generate rated voltage on an open circuit to the field current required to circulate rated armature current on short. The SCR value of machine impacts the operating characteristics, physical size, and cost of the machine. The larger the SCR, the smaller is alternator reactance (Xd) and inductance Ld. Conversely, the smaller the SCR, then larger is alternators reactance (Xd).
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The video below further explains in detail the Short circuit ratio: