Foreword
(This Foreword is not a part of ANSI/IEEE Std 421.1-1986, IEEE Standard DeÞnitions for Excitation Systems for Synchronous Machines.)
This standard deÞnes elements and commonly used components in excitation systems and contains deÞnitions for excitation systems applied to synchronous machines, for general requirements of a synchronous machine refer to ANSI C50.10-1977.
A synchronous machine excitation control system operating under automatic control is a feedback control system.Thus, the working group Terminology of the Excitation Subcommittee of the Power Generation Committee adopted deÞnitions that had common basis to excitation systems. Efforts were made not to conßict terms found in ANSI/IEEE Std 100-1984 , IEEE Standard Dictionary of Electrical and Electronics Terms, but to clarify or more fully deÞne terms as related speciÞcally to excitation of synchronous machines. The task of the working group can be divided into two areas