Anastasios , Karakatsanis S. Theoklitos VIBRATION ANALYSIS OF A DYNAMIC MAINTENANCE SYSTEM FOR ELECTRIC MOTOR’S During the last years there have become a lot of studies concerning the preventive maintenance of mechanical equipment and fault diagnosis, each one of them having a different approach. <...> This paper presents the development of a smart – dynamic maintenance system for electric motor’s failure prognosis. <...> The method is based on the analysis of the motor into his subsystems by using neural networks and by recording their relations and interactions. <...> In this model are also embodied the possible damages of every subsystem and its symptoms, respectively. <...> The objective goal of this analysis is to develop an algorithm for the calculation of the probability of showing the damage in a motor’s part according to its dynamic operational status. <...> The creation of a data basis reflects the techniques experience concerning the causes and the possible preventive actions that are necessary. <...> The suggested method is general and can be applied in every part or system of the mechanical equipment. <...> Finally, the paper presents a simple study case for the rotor and practical conclusions are drawn which can lead to a better focus on preventive maintenance. <...> Keywords: preventive maintenance, electric motor, failure prognosis, Neural Networks (NN), Dynamic Neural Networks (DNN). 1. <...> It is a fact that no equipment, especially when it comprises mechanical features or movable parts, can normally or continuously operate without having maintenance. <...> The necessary time for the restoration of service of the installations varies and it depends on the time of searching the cause, the availability of possible spare parts and the time of the main repair. <...> The preventive maintenance includes the replacement of the equipment that has finished the time of its useful life, despite being necessary or not, the control of the possible wear and fatigue points and the lubrication of the movable parts. <...> The criteria applied are the quality and reliability of the equipment, the time and the repair and replacement cost, the availability of spare parts and the storehouse capacity. <...> These methods consider as being stable the spare parts’ lifetime, the machines’ operating conditions and the pre-set tolerance and stressing of the spare parts, without taking into account the dynamic operational status of the equipment [2]. <...> The prognostic maintenance is based in the objective evaluation of the special functional and environmental equipment <...>