This paper presents a new user-friendly graphic interface for EMTP file generation using the Galaxy CAD system. Galaxy was originally designed for the schematic editing and simulation of digital systems. For this application the schematic editor is updated for power circuits modeling and include features such as parameter passing and hierarchical component generation. We found that this modular design feature not only reduces errors in input file preparation, but also allows for the creation of a library of hierarchical components. This graphic interface is available for the Macintosh, H p 9 o o 0 -3~~ and 4xx, Sun-3, Apollo and other Motorola MC680x0 processor based systems.