GB574618A - Means for the determination of the eccentricity of the conductor with regard to the dielectric in insulated wires and cables - Google Patents

Abstract

574,618. Locating conductors; detecting, Indicating, and locating faults. PLANER, V., and PLANER, F. E. Feb. 9, 1944, No. 2377. [Class 37] For determining the eccentricity of a conductor in a cable an alternating current flowing in the conductor produces inductive effects in elements designed for arrangement in different angular or radial positions with regard to the axis of the cable and these effects are compared. The conductor A<1>, Fig. 1, of a cable A<2> carries an alternating or pulsating current during passage of the cable through the extruder or other machine. Surrounding the cable is a non-magnetic or insulating ring formed in two parts B<1>, B2 hinged together at B<3>. The whole is mounted on a bench or a stand C<1>. The cable is centralised in the ring by rollers (not shown). On the ring are mounted two inductance coils D<1> containing cores of high permeability iron or nickel alloys in the form of wires, stampings, or dust. Each coil is arranged in a small casing E<1> the surface E<2> of which is pressed against the cable A by a spring E<4> in an outer casing E<3>. The casings E<3> are mounted on an inner ring F<1>, F<2> revolubly mounted in the ring B<1>, B<2> so that the angular position of the coils D<1> with respect to the cable may be varied. The halves F<1>, F<2> of the inner ring may be hinged together or otherwise joined, or the ring may be in one piece, as shown. Insulated rollers bearing on the surface of the cable may be carried by the casings E<1>. The coils D<1> are connected in opposition giving zero voltage if the conductor A<1> is central. If the conductor is eccentric a resultant voltage is induced which is a measure of the degree of eccentricity. By rotating the coils the eccentricity in different planes may be determined. Alternatively two pairs of oppositely connected coils may be fixed to the ring B<1>, B<2> with their axes at right angles. The two pairs of coils may be connected in a bridge circuit or through amplifiers to the two pairs of deflecting plates of a cathode ray oscillograph. Alternatively the position of the conductor within the dielectric may be indicated by a spot of light reflected from mirrors operated by the amplified voltages. The coils with their associated amplifiers may form part of a differential or bridge circuit using a well indicator such as a meter, cathode ray tuning indicator, or headphones. The bridge is balanced and the degree of eccentricity read from the balancing control. The bridge may be balanced by varying a resistance or by adjusting one of the coils radially by a micrometer screw, the eccentricity then being read directly from the calibrated screw head. The opposite coils may be replaced by a single coil having straight portions L<1>, L<2>, Fig. 4, parallel to the conductor. Fig. 6 shows an arrangement in which the voltage derived from the coil R<1>, depending on the eccentricity of the conductor, is compared with that derived from the conductor but independent of its eccentricity. This voltage is obtained from a toroidal winding P<1>, with or without an iron core P<2>, enclosing the cable Q. The coil R<1> may be rotatable round the cable either by hand or continuously by a motor. Instead of the toroidal coil a larger iron cored inductance coil may be mounted at such a distance from the cable as to make the voltage induced in it independent of any eccentricity of the conductor.