Advancements of power electronic technologies result in significant improvement in efficiency of power delivery to applications that consume or feed electrical energy to a grid. A transformer is an integral part of the power delivery process. Transformers used for power delivery must be efficient, compact and of low cost, and more importantly, they should be compatible with the connected source such as a power inverter. For a desired power density, the transformer design involves optimization of its electrical and magnetic circuits permitted by the thermal limits of core and copper. The limit of the magnetic circuit is indirectly linked to the winding design. Better use of core influences the design of the electrical circuit as well. Therefore, proper choice of core material and geometry is very important design consideration. This article reviews the domain of soft magnetic materials suitable for handling large electrical power from grid frequency to high-frequency applications. The paper covers different examples and elaborates the role of a transformer for one specific application. Review of transformer design considerations used in different applications, which are categorized based on their load characteristics, is a novelty of this work.