In cogenerator operation, the most important parameter considered by manufacturers is the number of operating hours, based on which the coupling connecting the motor to the generator is chosen. In this paper the authors conducted a study on the influence of factors leading to the occurrence of major flaws in cogenerator operation. Experimental tests were performed on three identical cogenerators placed in the same location, operating under similar conditions. The results of the experimental analysis have demonstrated that the most important parameter which must be taken into account in operation is the number of starts/stops (transient states) of the cogenerator. These actions involve mechanical shocks which can be characterized (interpreted) mathematically. The modelling of vibration phenomena is achieved through parabolic equations and the solution of these equations, obtained by different analytical mathematical methods, validating the results. Identifying and analyzing the main flaws found in cogenerator operation entitle us to recommend using elastic couplings with better characteristics than those utilized currently.