Induction generators are an important alternative for producing electric power because they have some advantages over synchronous generators. This paper analyzes the effect of induction generators on the transient stability studies of a laboratory electric power system (LEPS) that is composed of a squirrel cage induction generator interconnected to a synchronous generator. Three different arrangements of the LEPS are utilized: isolated, infinite bus-bar machine and multi-machine power system. Results are presented mainly for a three-phase fault applied at a bus-bar of the LEPS, determining the transient stability of both generators (synchronous and induction). Digital simulations are compared with test results for all configurations. The effect of the static load model characteristics in the assessment of the critical clearing time of each arrangement is also studied.