Damping of synchronous machines -analytical estimations versus finite element results

For dynamic stability studies, the supply of synchronous generators´ characteristic data is frequently requested. Most of these values, such as reactances, time constants and moment of inertia, are obtained by the electromagnetic design calculations. Others, such as the damping coefficient of the synchronous machine, are calculated more or less straight-forwardly for conventional damper configurations but not for machines with unconventional dampers, such as canned permanent magnet generators, for instance. In the paper, analytical approaches will be compared against the numerical determination of damping coefficients for different types of synchronous machines, such as salient pole, cylindrical and canned rotor generators.