Once again, this equation plots the power characteristics of the machine. Xs should be given from the manufacturer (1 - 1.8 for large machines I believe) while Ef can be calculated knowing that Ia is the current drawn from the machine and it depends on the load (but you can calculate the Ia...
useing the equivalent circuit, Vt is the constant bus (or terminal) voltage per phase and assum it the reference. Ef is the excitation voltage and d is the angle between Vt and Ef (the power angle).
Zs is the synchronous impedance and Xs is the synchronous reactance. Ia' is the conjugate of the...
