Spring and Damping Coefficients of Synchronous Machines and Their Application

This paper develops simple formulas for spring and damping constants of synchronous machines. These formulas include the effects of induced currents in the damper winding and field. An approximation to the effect of primary resistance in producing a negative damping torque is given. An equivalent circuit is given which can represent accurately the mechanical system of several engine-driven generators or compressors operating in parallel. It is concluded that the conventional representation of synchronizing power as full-load power over full-load angle is sufficiently accurate for most cases, but that it is well to have a more accurate method for special cases.