Short circuit current supplied by induction generators is becoming a matter of concern due to the increasing power share. Besides, in spite of that the induction generator operation principle is analogous to the traditional synchronic generator, its excitation and thus short-circuit supply is widely dissimilar. Induction generators are mainly applied to produce electric energy through wind turbines. Several papers showing analytical studies have been published, but just a few experimental results have come out. The present work is carried out mainly experimentally, extending the results by applying simulation software. Experiments using laboratory scale induction generator are presented. Four induction generator excitation types where investigated: remnant magnetism excitation, capacitor excitation, dc rotor excitation, and double feed induction generator. As rarely just one type of excitation is available, combined excitations were also studied. The research shows that induction machine short circuit contribution is closely related to excitation type and that the currently used initial and successive damped values represent an overestimation.