... constants of (7 .8- 7) and (7 .8- 8) are known. The parameters of the lumped circuit approximation can then be determined. For example, in the case of the two-winding approximation294 MACHINE EQUATIONS ... Synchronous Machines , Vol. 3 , Dover Publications , New York , 19 68 . PROBLEMS 297 Figure 7P-1. Short-circuit stator currents. ias, puibs, puics, pu0.1 second 8 0 8 80 8 80 8 PROBLEMS ... qo()()()()()=+′+′′+′+′′1111ττττ (7 .8- 1) As illustrated in Figure 7 .8- 2 and Figure 7 .8- 3 , the asymptotic approximation of (1 + τ s ) is used to match the plot of the magnitude of X q ( s ) versus frequency....