This document specifies the principal characteristics of alternating current (a.c.) generators under the control of their excitation control system when used for reciprocating internal combustion (RIC) engine driven generating set applications and supplements the requirements given in IEC60034-1. It covers the use of such a.c. generators for land and marine applications, excluding generating sets used on aircraft or to propel land vehicles and locomotives. NOTE For some specific applications (e.g. essential hospital supplies, high-rise buildings, operation parallel with the grid), supplementary requirements can be necessary. The provisions of this document can be regarded as the basis for establishing any supplementary requirements.For a.c. generating sets driven by other reciprocating-type prime movers (e.g. steam engines) the provisions of this document can be used as basis for establishing these requirements.