The effect of two - mass system factors on the quality and quality of transient states , particularly the effect of mechanical rigidity has been studied in this research . Besides , mathematical expression which can calculate the optimal value of rigidity and provide the minimum extent of electromechanical vibrations have been obtained . Characteristics and schematic diagrams that prove the effect of mechanical rigidity on the behaviour of the transient state are illustrated . These methods help to improve the performance of automatic control systems in order to provide the minimum dynamic loads without reduction of the machine productivity.