The core losses quantification of magnetic components with geometrically diverse cores for power converters remains a challenge and an area of active research. By using finite element analysis software Ansys Maxwell, a simulation method for core losses calculation under PWM voltage excitation is proposed based on the modified Steinmetz equation(MSE) in this paper. The magnetic properties measurement and model of core material are specified, which are basis of core losses simulation. Furthermore, the work conducts a comprehensive error analysis to identify primary sources of simulation inaccuracies, accompanied by targeted mitigation strategies. To validate the methodology, core losses of a ferrite EE shaped core are simulated and subsequently compared with experimental measurements acquired through the DC power method. The close agreement between simulated and empirical results demonstrates the efficacy of the proposed methodology.