IEEE/AIEE 66-1957

This Guide presents general recommendations for determining, by approximate methods from nameplate data and by more exact methods from design data, the short-circuit characteristics of direct-current motors and generators. Both methods are applicable to General Purpose, General Industrial Mill Motors, and Special Purpose direct-current machines. This includes constant-speed and adjustable-speed motors and machines with and without compound windings, and with and without compensating windings. 1.0.2 This Guide is intended to help those concerned with the transient characteristics of directcurrent machines and direct-current systems and the effects of these transients on their operation. The calculated values of rate of rise and peak armature current will facilitate the proper selection of system components which will safely withstand the mechanical and thermal stresses during fault. When only nameplate data is available, the approximate methods presented will yield results sufficiently accurate for estimates. Values computed by this method will be high, in general, thus on the safe side. Additional data from machine design sheets, or tests, will permit use of the more exact methods of computation with the view of minimizing the size of components and circuit protective equipment

The purpose of this Guide is to: (a) Review the factors that affect the short circuit characteristics of direct-current machinery. (b) Recommend equations for calculating the transient armature and field current from design parameters. (c) Recommend methods for approximating the rate of rise and peak value of armature current from nameplate data. (d) Discuss the causes of flashover and its effect on short-circuit current and effective armature-circuit resistance.

- Inactive-Withdrawn.