The influence of various factors upon the leakage reactance of transformers

This paper investigates the leakage reactance of transformers by means of Roth´s potential-vector method of analysis. The potential vector is divided into three components. The first component gives rise to the normal reactance as calculated by Kapp´s equation; this is termed the ¿axial reactance.¿ The second, which is responsible for additional leakage reactance, is termed the ¿radial component¿. The third, which does not lend itself to easy mathematical treatment, is shown to modify the axial term, giving a closer degree of approximation by its inclusion. In order to enable the total leakage reactance of various winding arrangements to be calculated, three Tables are provided. Thus it is possible to allow for the effects of cooling ducts, tappings, and end-turn reinforcement. In Appendix I a comparison is made between the calculated and tested values of the leakage reactance of two commercial transformers having non-uniform distribution of ampereturns.