I. Introduction
The transformer is a device fundamentally based on Faraday's law of induction. Its design requires knowledge of electromagnetism, magnetic circuit analysis, electric circuit analysis, loss mechanisms, and heat transfer. Initially, transformers were designed for low-frequency bulk power transmission and distribution. Indeed, the power transformer is one of the main reasons for the widespread use of ac power systems. With the advent of power electronic converters operating at ever increasing frequencies, the need for high-frequency transformers emerged. Thus, the transformer design problem remained an active research area.