The short-circuit characteristics of D-C generators

KNOWLEDGE of the short-circuit characteristics of d-c machines is an essential factor in the design of d-c electric systems having a large low-voltage machine capacity concentrated in a small area. This information is particularly important in the design of systems such as those encountered aboard ship where circuit breakers, fuses, relays, and other protective equipment must be so applied and co-ordinated as to provide a high degree of reliability and service continuity. Available information relative to d-c short-circuit currents has been limited to theoretical analyses based on formal solution of the differential equations of current flow and the machine inductance and resistance values. As a tool in the routine design of d-c systems, this information has not been adequate, particularly when estimates must be made of the effect of fault resistance, choice of machine construction, and so forth.