Analysis of an Alternator with Two Displaced Stator Windings

To improve efficiency and alleviate certain limitations in large generators, two separate stator windings have been suggested. The behavior of an alternator with two 3-phase stator windings displaced by an angle e;, is analyzed by means of an orthogonal transformation of the a, b, c; A, B, C; and fd variables into a new set: dl, ql, 01; d2, q2, 02; and fd. For balanced operating conditions the differential equations with the new variables have time-indenendent coefficients. Thus a phasor diagram can be drawn using self and mutual reactances Xd, Xqv X12d and X12q, determined from flux linkages. The latter are based on flux plots obtained bysolving the quasi-Poissoniandifferentialequation. The characteristic parameters for a specific operating condition are calculated for a 1200 MVA, 24 kV, 60 Hz, two-pole turbogenerator, and test data are presented covering single circuit operation on a 2-circuit generator with 600 belts connected as an alternate pole and alternate belt type double winding machine.