Study of Field Weakening Traction Direct-Current Engine with the Help of the Computer simulation. Analyzed traction engine modes of electric train, equipping it exiting coils of shunting electrical circuit with non-contact high-speed commutation element. By means of computer modeling the results of transient process are obtained in circumstances of contact network voltage rise while electric train is accelerating, as well as in case of engine keeper’s circuit insulation fault. The results reflect the performance of the electronic protective knot on the basis of current sensors signals, according to the algorithm used.