Novel Technique to Compute the Leakage Reactance of Three-Phase Power Transformers

A practical and novel technique to compute the leakage reactance of step lap-core power transformers is presented. It can be applied to helical or continual disc windings. The developed technique is based on computing the magnetic flux lines produced by each active conductor in the windings. Thus, the magnetic linkages are obtained by applying the concept of geometric mean distance of rectangular areas to the magnetic potential. The obtained analytical formulae enable straightforward calculation of the transformer reactance with better accuracy than traditional methods currently used in the design of power transformers. Leakage reactance was computed for 12 power transformers with different coil configurations, and the results were compared with results calculated from the short-circuit test. A difference of no higher than 3% was obtained between values measured with our proposed technique and values calculated with the short-circuit test.