GB190701855A - Improvements in and relating to Alternating Current Distribution Systems especially applicable to Electric Railways. - Google Patents

Abstract

1855. British Thomson-Houston Co., and Woodbridge, J. E. Jan. 24. Electric railways.-In alternating-current systems of distribution such as are used in electric railways, the potential drop in the return circuit is minimized by employing a cable having a magnetic sheath and containing two conductors which carry the supply and the return currents, thus constituting a combined continuous cable and booster. By these means the greater part of the drop in the return conductor is transferred inductively so as to add to the drop in the supply conductors. Fig. 1 shows the invention as applied to a single section of overhead or track conductor of a railway system. A cable having a minimum reactance is used, for example a concentric cable having a central conductor a surrounded by a cylindrical conductor b, the whole being enclosed within, but insulated from, an iron or steel sheathing c. A lead sheathing d may also be provided round the inner conductor or round both conductors inside or outside the magnetic sheathing. The outer conductor b forms part of the return circuit, being connected in parallel with the track rails g, which may serve to carry the magnetizing-current of the cable transformer ; or a third conductor may be used for this purpose. Fig. 2 shows the application to a system having a number of insulated sections of supply conductor. The outer conductors b<1> of the cable sections are connected tagether by conductors b<11>, and each is also connected to the track rails g' at or near the point of connexion of the inner conductors with the supply conductor e'. The magnetic circuit of the cable may be formed by iron troughing in which the cable is laid.