Analysis of Minimum Excitation Limits of Synchronous Machines

The paper analyzes the minimum excitation limits being fed from the stator terminals of a synchronous generator. Mathematical methods are developed for evaluating the effectiveness of a new limit in its different settings and for comparing its characteristics with the "basic limit," which has some of the features of the limits often applied. The effectiveness and characteristics of the new limit can be changed over a wide range in order to match them to special demands. Depending on its setting, the new limit either prevents or permits the generator to work beyond its steady-state stability curve in the steady state.