Abstract ISO 8528-3:2005 specifies the principal characteristics of Alternating Current (a.c.) generators under the control of their voltage regulators when used in generating set applications. It supplements the requirements of IEC 60034-1. ISO 8528-3:2005 applies to a.c. generators used in a.c. generating sets driven by reciprocating internal combustion (RIC) engines for land and marine use, excluding generating sets used on aircraft or to propel land vehicles and locomotives. For some specific applications (e.g. essential hospital supplies, high-rise buildings) supplementary requirements may be necessary. The provisions of ISO 8528-3:2005 should 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 ISO 8528-3:2005 should be used as a basis for establishing these requirements.