The article presents research results and issues related to of magnetic component of electromagnetic field on the environment and electronic systems used in the electric traction unit. The electronic systems used and built into an electric power unit are operated in a wide variety of environmental conditions. Electrical and electronic systems with different purposes coexist on the vast railroad area, and an important operational problem, apart from environmental changes in which these technical objects are operated, is also the issue of external and internal electromagnetic compatibility. Depending on the extent of the railroad area, the intentional or unintentional emission of electromagnetic fields over a range of frequencies, the construction, technical configuration and method of ensuring electromagnetic compatibility for the electrical and electronic systems in use and electronic systems in use are different. It is necessary to skillfully and appropriately use all measures included in the electromagnetic compatibility pyramid to ensure the appropriate level of robustness, immunity and susceptibility of the above mentioned systems. Due to the impact and propagation of electromagnetic waves in the railroad environment, individual frequency bands of interfering signals should be considered separately for the whole spectrum of interfering signals. The article presents the results of research on the generated magnetic fields from the very low frequency (ELF) range by electric power units. Diagnosing the electromagnetic environment over the entire frequency range enables the realization and proper protection of the electrical and electronic systems used in an electric power train from the effects of unintended interference. Knowledge of the parameters of interfering signals - e.g. amplitude, frequency range, spectrum, etc. - will enable designers of electrical and electronic train systems systems to properly protect these facilities from adverse environmental conditions.