Ferromagnetic materials are widely used in the construction of electromagnetic devices. In ferromagnetic materials, the internal magnetic fields originated by electrons spinning are well pronounced. When the ferromagnetic material is submitted to an external magnetic field, the domains will be affected, firstly, by wall displacements. The total iron losses in ferromagnetic materials can be divided in hysteresis and dynamic losses. Historically, several researchers studied iron losses and proposed models to simulate their behavior. The dynamic components of iron losses are introduced considering the most employed experimental devices used to separate them: the classical Epstein’s frame and the Single Sheet Tester. Hysteresis losses are related to the irreversible displacement of the magnetic domain walls when they are submitted to a magnetic field. For small frequencies, the hysteresis losses are preponderant. As the frequency increases, the dynamic losses become relevant.