Soft-magnetic materials in large turbo-alternators

The economic design of large turbo-alternators is greatly affected by the properties of the soft magnetic materials available for building them. The saturation magnetization of the stator iron effectively determines the power output of a machine of given physical size. Losses in the iron waste power, and so must be minimized, while increasing the depth of a stator core, to reduce losses, leads to increased transportation costs. Localized loss concentrations, particularly in the end region, can cause operational difficulties; the severity of the associated ´hot spots´ depends not only on the electro-magnetic properties of the iron but on the thermal properties as well. Mechanical rigidity of the assembled core is also important; magnetically favorable materials might be rejected by a designer if too flexible.