This paper presents a methodology for a convenient modification of induction motor equivalent circuit parameters, taking into consideration switching frequency iron losses in case of inverter supply. The method is based on the determination of harmonic iron losses in laminated iron cores under nonsinusoidal excitation by using a particular three-dimensional (3-D) finite-element model adopting a reduced scalar potential formulation. Eddy currents in iron laminations are considered by means of convenient surface current densities. Experimental verification is performed in case of a 20-kW experimental setup.