Calculation of the magnetic field of rotating machines. Part 5: Field in the end region of turbogenerators and the eddy-current loss in the end plates of stator cores

A method of calculating the magnetic field in the end region of a turbogenerator is described. Allowance is made for nonmagnetic stator-core clamping plates and for the magnetic shaft and casing of the machine. The effect of a magnetic rotor-retaining ring is studied, the ring being regarded as a tube of finite permeability separating the stator and rotor end windings. Calculations are compared with experimental results. The field calculated at the surface of the stator-core end plates is used to estimate the eddy-current loss in these plates, and the effect upon this loss of the retaining-ring permeability and the stator-winding cone angle is considered.