Simplified computation of voltage regulation: With four-winding transformers

COMPUTATIONS of voltage regulation ordinarily are based on the use of an equivalent circuit for the four-winding transformer, using either a six-branch network, or preferably the eight-branch network described by Starr.
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Determination of the equivalent circuit — a tedious analytical task — appears to be unnecessary, however. As a simpler alternative for determining voltage regulation with load on three windings and the fourth winding acting as a source, the necessary constants may be obtained directly from the usual two-terminal impedances.