There is analyzed in details the complicated process on which the dynamic stability of a high power synchronous machine (HPSM) depends. There is pointed out the necessity to use dynamic angular characteristics in the stability analysis and the fact that the speed of rotating magnetic field can be widely variable, beyond the operation in synchronism. It is shown that there is an infinity of dynamic angular characteristics and that mathematical models are an efficient and fast way to respond if a given disturbance of a steady state synchronous operation leads or not to loosing synchronism.

Keywords: Synchronous machine, Dynamic stability, Simulation