Purpose: To develop a methodology for determining energy consumption in synchronous traction generators depending on implemented workload mode. To calculate traction characteristics of a locomotive it is necessary to obtain analytical dependences of energy losses in a synchronous traction generator from rotation frequency of its shaft, electric current and voltage at rectifier plant. To solve the problem of determining significance of various components of losses in a synchronous traction generator under different operating modes. Methods: Investigation of all components of energy losses in a traction synchronous generator. Conclusion of analytical dependencies that allow calculating all components of losses in generator depending on its design parameters by obtaining constant coefficients that depend on design parameters of generator. Results: The values of capacity spending for energy conversion in a synchronous traction generator are determined. The obtained dependences allow us to perform refined analysis of losses in a traction drive. It is shown that the capacity of mechanical losses at a nominal speed reaches 50 kW, capacity of electrical and magnetic losses can reach 20 kW. Practical importance: The results obtained allow us to clarify the amount of energy consumption in a traction drive of locomotives and improve the accuracy of traction calculations. The nature of the change in losses in a synchronous traction generator depending on speed, voltage and current at the output of rectifier plant and its design parameters is shown. The results can be used, among other things to clarify traction characteristics of locomotives.