This book has presented a theoretical and practical knowledge base related to DC/DC converters for the light rail vehicles. It describes the difficulties connected to the development of power electronics for the rolling stock, provides an analysis of state of the art issues and technology trends in this demanding application field. Analysis includes classification of design requirements, topologies, components, optimization methods, etc. A new power scheme topology for improving power density and reducing component stresses and system volume for the implementation in the onboard auxiliary power supplies has been recommended, analyzed and tested. Practical part of this research covers the design issues of high-frequency inverter and rectifier stages, proposals for compact layout of power electronic stack with new advanced cooling technologies. The developed topology as well as the control methods and algorithms, power layout design, user interfaces, etc. can be directly applied on other electrical transport (trains, electric cars, etc.), on industrial facilities (welding machines, telecom systems, etc.) as well as in aerospace and marine industries.