Page 113 - Handbook of Electrical Engineering

94 HANDBOOK OF ELECTRICAL ENGINEERING

Figure 4.5 Open-circuit voltage in per unit versus exciter field voltage in per unit. For use in determining the
SE75 and SE100 parameters of the exciter.

V a31 − V a32
S 3 = (4.15)
V a32
Use V fd1 as the reference output voltage and convert V fd3 into a per unit factor of V fd1 ,
denoted as V fd3pu .
V fd3
V fd3pu = (4.16)
V fd1
By simple proportions,
(4.17)
V a32 = V a12 .V fd3pu
Choose a factor u> 1, such that,

V a32 V a12 .V fd3pu
u = = (4.18)
V a22 V a22
Therefore,
V a12 .V fd3pu
V a22 = (4.19)
u
Substitute (4.19) into (4.14), and (4.17) into (4.15),

V a21 − V a22 BVf d2
S 2 = u = Ae (4.20)
V a12 V fd3pu