The Contribution or Motors and Generators to a Short Circuit Results of Laboratory and Marine Tests

Short-circuit currents, which are particularly high on ships, result from the combined contribution of generators and motors. This phenomenon can be analyzed with equations expressing the transient conditions of 3-phase rotating machines. Some simplification of these equations allows an easy calculation of short-circuit currents; however, tests are necessary to determine accurate maximum peak and symmetrical component values, especially for the motors. In the specifications of the International Electrotechnical Commission (IEC), some coefficients which allow quick evaluation of the contribution of motors to short-circuit currents have been standardized; these are confirmed by the laboratory and marine tests described in this paper.