This book focuses on the role and application of tap changers to power transformers and the power transmission industry in general. Starting with an elementary introduction to the fundamentals of tap changers, the book discusses the evolution of resistance tap changers and their current applications. It also includes the most recent technologies in the field like the vacuum and reactor tap changers, and discusses the driving mechanisms, operations and maintenance. This book can be a very useful reference for power systems professionals, engineering consultants, transformer manufacturers, and R&D organizations in the specification, installation, operation and maintenance of tap changers.