The use of single-core armoured cables for alternating currents

The paper is intended to form a corollary to that of Professor Cramp and Miss Calderwood ¿ and deals with the losses involved in the distribution of alternating currents in sheathed cables in which the sheath is of magnetic material. Single-core rubber-insulated cables, each enclosed in a separate iron tube, and also single-core cables armoured with one or two layers of galvanized iron or steel wires, are dealt with, and experimental data are given showing the measured losses in each case. It is shown that, while the losses due to induction in a tube are considerable, those in a wire-armoured cable are comparatively very small, and also that the distance separating the individual cables forming a circuit has very little effect in determining the losses involved. In the case of the wire-armoured cable, also, the connection of the sheaths of separate cables so as to form a closed sheath circuit has no appreciable effect upon the losses, and the current which will flow in such a circuit is so small as to produce no considerable heating.