Screened coil for few turns flat winding - leakage flux is reduced by close fitting screen with overlapped joints

摘要

A coil carrying alternating current, especially one of a few turns of a flat conductor, such as used for inductive linkage between a tracked vehicle and a trackside conductor having a U shaped frame core of ferrite with a winding (3) on the yoke (2) surrounded by a closely fitting screen (4) leaving the pole faces (5) of the core exposed. To prevent the screen acting as a short-circuited turn it is electrically interrupted by an overlapping joint (6) with an electrical insulator, which may be an adhesive coating between the overlapping surfaces. The overlap joint extends round the interior of the core over the full length of the screen so as to coincide with that of the magnetic flux in the space enclosed by the screen and reduce leakage flux.