The objective of this work is to provide theoretical substantiation for the possibility of using power factor as a criterion in the development of optimized automatic control systems for AC electric rolling stock traction drives. The stated objective has been achieved through the solution of the following tasks: development of an algorithm for applying traction drive power factor as an optimization criterion, taking into account stochastic disturbance effects acting on the traction drive from the traction power supply system and mechanical load; development of a structural scheme for an optimized automatic control system of electric rolling stock traction drives, in which the proposed algorithm is implemented. The most important results are: the obtained analytical time dependency of the traction drive power factor, representing a convolution of two-time functions—efficiency and active power utilization coefficient of the traction drive—and the developed algorithm for eliminating stochastic disturbance effects acting on the traction drive from the traction power supply system and mechanical load. The significance of the obtained results lies in improving the quality of AC traction drive control. An electric locomotive traction drive with field-oriented control (FOC) of asynchronous traction motors was selected as the research object. This will enable improved regulation quality in the construction of an optimal automatic control system for traction drives.