Practical model of the axial magnetic field in the end region of large turbo-generators

Abstract : Purpose The axial magnetic field occurs in the end-region of large turbo-generators is known to induce hot points or voltages between laminations, that may cause insulation breakdown and thus stator faults. Design/methodology/approach It is important to dispose of simple methods for estimating the axial flux rapidly with regard to the operating point of the machine. Findings The authors provide a practical model of the axial magnetic field based on a simplified vector diagram. The parameters required to build the vector composition of the flux densities are assessed with a limited number of finite element method simulations of the whole end-region of the machine. These simulations were validated by an experimental test on a real turbo-generator. Then the axial flux density was simply estimated for various operating points. Originality/value The originality of the paper concerns the practical model of the axial magnetic field based on a simplified vector diagram.