Physical concept of leakage reactance

LEAKAGE REACTANCE has been the subject of discussion in the technical literature from time to time since the adoption of alternating current for the generation and utilization of electric power. In the beginning it was customary for the designer to estimate the number of leakage lines per ampere inch of the embedded portion and end connections of the windings and multiply these by the respective lengths to obtain the reactance. Early writers treated this subject under the title of magnetic dispersion and took account of its effect through the use of a leakage coefficient. About the leakage coefficient R. E. Hellmund writes: The chief reason for determining this value is, however, the fact that it fixes directly the excellence of a motor in almost every respect and, therefore, the values obtained for this factor form a direct means for determining the relative merits of various designs. If properly designed a motor will always be better the smaller the leakage coefficient. The leakage coefficient no matter how it is defined is always the ratio between the effects of the leakage field and the main field.