Magnetic materials are typically used in the construction of inductors and transformers for power electronic applications. Their selection (material and size) is a critical task that demands good knowledge of the topology under study. An incorrect design may lead into a low-level saturation flux density, additional losses, and negatively affect the overall performance of the power converter. Traditionally, the Steinmetz equation is used to evaluate the core losses of magnetic materials under sinusoidal excitation; nevertheless, in modern power electronic converters the current and voltage waveforms across inductors and transformers are far from sinusoidal, thus, other methods must be considered. The core losses estimation for three different magnetic materials under different waveform conditions is the main aim of this paper. Analytical and experimental results on a 5 kVA three-level half-bridge power converter are compared to evaluate material losses under rectangular-voltage waveform with different duty cycles (D) and switching frequencies (f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">sw</sub> ).