Per-Unit System for the Dual-Excited Synchronous Machine

The per-unit systems used for the conventional synchronous machine are not equally applicable to the dual-excited one when the field windings are not located on the rotor axes. This is because the mutual inductances between any of the two inclined field windings and the armature windings are dependent on the permeance in both the direct and the quadrature-axis. In this paper, a sound per-unit system, taking this dependence into consideration, is suggested for this machine. The system is derived in such a way so as to provide normalized equations representing the physical nature of the magnetic couplings between the different machine circuits.