Three-phase Induction Generators (IGs) are increasingly being used as smallscale energy producing devices in nonconventional energy conversion systems. Both squirrel-cage and wound rotor types of induction motors used as generators are popular in this regard. The aim of this paper is to discuss critically the important contributions of researchers on the applications in both grid-connected and isolated modes of operations and critical evaluation of performance of these generators under different operating conditions. The major focus has been on the evaluation performance of squirrel-cage induction motor used as Self-Excited Induction Generator (SEIG), and both experimental and theoretical results are provided to represent the important characteristics of this generator. Finally, the future trend of research in this field has been pointed out.