Subtransient reactances of synchronous machines

THE THEORETICAL approach so far made in the development of formulas for the direct- and the quadrature-axis subtransient reactances is based on either proportioning the current in the pole-tip bar, depending on its permeance, or evolving an equivalent damper winding on the assumption of sinusoidal distribution of damper currents. Both these methods have their limitations when applied to the case of salient pole synchronous machines. The purpose of this digest is to outline an accurate method of determining the subtransient reactances by estimation of the induced magnetomotive force of each of the rotor circuits in terms of the applied sinusoidal armature magnetomotive force from a knowledge of the field forms for the two axes and the leakage permeances of the damper and the field windings.