Most of the relevant literature related to power transformers design methodologies can be broadly classified into two categories. The first category includes methodologies that adopt a mixed approach of approximate analytical and empirical design equations. The second category includes methodologies that are more accurate yet require expensive software tools and/or massive computation resources. In order to make this book self-contained, characteristics of the main common materials used in fabricating power transformers were reported. Moreover, important basics related to power transformers operation and design aspects were reviewed. The main contribution of this book is its detailed presentation of computationally efficient and reasonably accurate specifications-oriented initial design methodologies that incorporate some guidelines inferred from relevant electromagnetic field analysis studies.