For the accurate electromagnetic simulation of devices containing laminated conductive cores including eddy current effects it often turns out that the full discretization of each sheet of a laminated core and the space between two sheets is computationally costly. The factors considered in reducing the effort refer to the finite integration method. By means of an analytical model the equivalent conductivity of a laminated iron core in the direction normal to the sheets is determined. The applicability of the model is demonstrated by comparison of measured shading ring sensor data and numerical results, performed by the W3 module of the program package MAFIA.