Page 114 - Handbook of Electrical Engineering
P. 114

AUTOMATIC VOLTAGE REGULATION      95

           And,

                                             V a31 − V a32     BVf d3
                                       S 3 =            u = Ae                           (4.21)
                                             V a12 V fd3pu
           Divide (4.21) by (4.20)

                                     S 3   B(Vf d3−Vf d2)
                                        = e
                                     S 2
           From which,

                                                S 3
                                          log e
                                                S 2
                                     B =                                                 (4.22)
                                          V fd3 − V fd2
           Also,
                                           (V a31 − V a32 )
                                     S 3
                                        =
                                     S 2  (V a21 − V a22 )u
           Since
                                         V fd3
                                     u =       by proportion from (4.18)
                                         V fd2
                                     S 3 = Ae Bu Vf d2
                                     S 2 = Ae BVf d2

           Hence,

                                     log S 3 = log A + uBV fd2                           (4.23)
                                                e
                                        e
           And,
                                     log S 2 = log A + BV fd2                            (4.24)
                                                e
                                        e
           Multiply (4.24) by u, and subtract from (4.23),

                                     log S 3 − u log S 2 = log A − u log A
                                       e         e       e         e
                                                     = (1 − u) log A
                                                                e
           Therefore,


                                               A 1−u  =  S 3
                                                        u
                                                      S 2
           Hence,
                                                      1/(1−u)
                                                    S 3
                                               A =
                                                     u/(1−u)
                                                    S 2
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