The invention refers to an electric cable for use as phase winding in a three-phase alternating-current winding for linear motors in which the phase windings are fixed in meander-like course in the grooves of an elongated conductor, the cable having a metallic conductor, an inner conductive layer surrounding the conductor, an insulation disposed over said conductive layer, an outer conductive layer surrounding said insulation and a sheathing of electrically conductive material placed over this.
Such a cable can be noted from Federal Republic of Germany Pat. No. 30 06 382. Said cable is formed in three strands into a prefabricated winding of a linear motor, which winding can be wound as a unitary structure on a reel, transported to the place of installation and inserted there in particularly simple manner into the grooves of the inductor of the linear motor. The cable must be capable of being readily worked into a winding and in its worked condition retain its electrical and mechanical properties for a long time in order to produce a traveling magnetic field. This includes, for instance, a tight, firm seat of the inner conductive layer on the conductor, a high conductance and high current-carring capacity of the shield which is formed by the outer conductive layer and the conductive sheathing. The conductance and the load-carrying capacity of the shield must be such that, on the one hand, charge currents do not substantially increase the shield potential and in the event of a grounding fault, the current necessary to detect the grounding can flow and that, on the other hand, there are only negligible losses by secondary currents which flow in the conductor loops of the intersecting cable strands and a ground strand as a result of the induced voltages. One attempt to meet these goals is taught in the construction of a cable in accordance with Federal Republic of Germany Pat. No. 30 06 382. However, no indication as to how the requirements are to be satisfied can be noted from that patent.