Some Proximity Effect Formulas for Bus Enclosures

Proximity effect currents, caused by parallel conductors in proximity with each other, are important chiefly because of the increase in resistance loss that they cause. Large, nonmagnetic tubular enclosures for buses have low resistances, and special formulas are required. Formulas are given for open-circuit 3-phase enclosures and for bonded single-phase enclosures. The measurement of such circuits, giving curves of loss versus frequency, is best made on small metallic models at about 1,000 cycles, according to experience with other skineffect problems. The results can be adapted very precisely to 60-cycle cases, and they are needed to check the algebraic formulas and to determine the end effects in open-circuit tubes. Electromagnetic centimeter-gram-second units are used throughout.