Abstract: In this study, a new approach for evaluating the energy losses at start-up conditions for a separately excited DC motor is developed. It is slightly different from the known methods of evaluation the starting losses described in most references of electric drive. Dynamic equations and analytical results have been derived. The obtained results ensure the justification of accuracy of this approach in evaluation of the losses. In further studies, it is expected to extend the approach for the series excitation DC motors and also for the asynchronous motors.