Dynamic behaviour investigation of electromagnetic force densities

The present paper deals with the electromagnetic forces due to the rotatory magnetic field in an alternating current machine. The time dependent pulsations of the elliptic force density field are investigated. Applying the method of Maxwell stress the distribution of the electromagnetic force densities is studied in theoretical aspect at first. A factor is defined for a numerical valuation of dynamic force density behaviour in a period. As a numerical example the electromagnetic force density field is considered in the end region of 200 MW turbine-generator. The calculations are made using FEM. On the basis of the defined factor the dynamic loads rate is estimated and the relevant conclusions are drawn with respect to the critical regimes and the critically loaded parts of the device. It is shown that the approach based on the local electromagnetic forces studying could to be used in detailed analysis and computer aided design.