Inductances of a Portion of the Armature Winding of Synchronous Machines

The main and leakage inductances are found from the flux linkages with the short-circuited part of the armature winding. The mutual inductances between the short-circuited part of the armature winding and the remaining part of the armature and rotor windings are proportional to the main inductance. A synchronous machine with a single phase-to-ground fault embracing a number of turns, Nf, can be regarded as an imaginary symmetrical machine having the armature winding with Nf turns in each phase and the same rotor construction as the actual machine. With such a provision, the synchronous and subtransient inductances of a part of the armature winding can be determined by the general theory of a synchronous machine. The damping of harmonic fluxes by currents in the short-circuited rotor winding is taken into consideration by the calculation of the subtransient inductances. The measurements of the subtransient reactances of portions of the armature winding have been performed on a synchronous machine. The calculated subtransient inductances deviate from the measured values; however, they can be used for the internal fault calculations within the permissible engineering accuracy.