Many of the electric motors, including squirrel cage induction motors, which operate on the factories, have already exhausted their resource which was guaranteed by the manufacturing plant. Many of them however are still able to perform the assigned tasks. Their use therefore is not stipulated for by the terms of service, but by their technical condition. Hence, their reliable operation significantly depends upon the precise information on the residual resource which is necessary to know. The same is applied to the new electric motors, in the course of operation of which there are many different overloads which may dramatically decrease the remaining resource. The most reliable methods and means for diagnosing squirrel cage induction motors are those that are provided for continuous monitoring of the technical condition of electric motors during their operation. Therefore, it is chosen to determine the residual life of an electric motor during its operation. As the diagnostic features for determining the residual life of a squirrel cage induction motor, there had been chosen the following parameters: currents in each phase of the electric motor, the temperature of the most heated point of the winding, the speed of change in the temperature of the winding, the temperature of the bearing units, the level of vibration. To synthesize the structure of the device aimed at determining the residual life of the electric motor, there had been used the apparatuses of sequences. The paper shows the process of synthesis for two values of current, two values of winding temperatures, two values of speed of changes in winding temperatures, two values of bearings temperature and two vibration values. There had been presented the mathematical model of functioning of the block of calculation of the residual resource of a squirrel cage induction motor in the form of a system of sequences. On the basis of the received sequential model there had been synthesized a functional diagram of the block of calculation of the residual life of the squirrel cage induction motor which enabled to develop the structure of the device to determine its residual resource. The received structure of the device allows to control the parameters of the electric motor during its operation.