In this paper an automated multiobjective optimisation based on fuzzy logic is applied to the magnetic core design of induction machines. The fuzzy logic is used in order to merge all the objectives of the vector optimisation in a single scalar function, so that the problem can be handled through a scalar optimisation algorithm. The estimation of the objectives is obtained through the field analysis performed by the Finite Element Method (FEM). The proposed procedure is used to improve performances of industrial induction motors where iron losses, electromotive forces and weight are optimisation objectives, while airgap thickness, external stator radius and stator tooth width are considered as design parameters