Abstract This paper presents a methodology for determination of harmonic iron losses in laminated iron cores under non sinusoidal excitation. The methodology adopted is based on a particular 3D finite element model by using a reduced scalar potential formulation. Eddy currents in iron laminations are considered by means of convenient surface current densities. Experimental verification is performed by comparing computed and measured leakage field in an E-shape laminated core case. A convenient modification of induction motor equivalent circuit parameters is proposed enabling consideration of switching frequency iron losses in case of inverter supply.