A field plot of a turbogenerator with a massive rotor on the basis of the actual current distributions during a sudden short circuit

A well known fact is not to neglect the difference between the calculated and the measured reactance values of a turbogenerator with a massive rotor. This difference can be minimised on the basis of an extended mathematical model which considers the influence of the eddy currents in the massive parts of the machine. The effects of the eddy currents in the massive rotor can be modelled by an additional complete damper cage. For a standard built damper cage there are analytic formulas for its parameters. But for a damper cage, which should replace the effects of the eddy currents in the massive rotor, the parameter identification is difficult, because the calculation of the eddy current distribution in the rotor teeth is complex. This is the reason why the parameters of this second damper cage are found by field plots of the machine. These field plots are based on currents which are measured during a sudden short circuit