GB443017A - Improvements in lead-in conductors for transformers, switchgear and like electrical apparatus enclosed in metal casings - Google Patents

Abstract

443,017. Lead-in conductors. SMETHURST, H., 147, Victoria Road, Fallowfield, and BANCROFT, F. E., 19, Delaine Road, Withington, both in Manchester, BURROWS, G., Lynton, Fownhope Avenue, Sale, Cheshire, and ASSOCIATED ELECTRICAL INDUSTRIES, Ltd., Crown House, Aldwych, London. July 18, 1934, No. 21055. [Classes 36 and 38 (i)] A lead-in device for heavy current or high frequency alternating current electrical apparatus enclosed in a metal casing comprises a pair of insulated coaxial conductors adapted to extend through an aperture in the metal casing and having terminals disposed outside the metal casing. The ends of the conductors within the casing connect to the terminals of the enclosed apparatus. The coaxial arrangement of the conductors prevents inductive heating of the casing due to the current flowing through the lead-in device. As shown in Fig. 1, the device comprises a tubular metal body 4 passing through an aperture 2 in the wall 1 of a metal container of an electrical apparatus, the body, which forms a part of the outer conductor of the lead-in, being supported by a flanged insulating bushing 3 which is clamped to the wall 1 and to which the body 4 is secured by a nut 6. A metal tube 8 is welded to the foot of the body 4 and completes the outer conductor. The inner conductor consists of a tube 9, the lower end of which is closed by a metal member 12 having a flange 14 adapted to bear against an insulating ring 15 which engages a metal ring 8a secured to the end of the tube 8. The upper end of the inner conductor is screw threaded and passes through an insulating ring 10 which fits on the shouldered end 11 of the body 4. A nut 17, which engages the screw-threaded upper end of the inner conductor, is tightened against the insulating ring 10 to secure the inner and outer conductors together. At the lower end of the lead-in, terminals 13, 26 are provided, whilst at the upper end, the inner conductor is furnished with terminal nuts 21 and the body 4 is formed with a screw threaded recess 25 adapted to receive a terminal member (not shown). To provide for cooling of the lead-in, apertures 23, 24 are formed in the inner conductor and body 4, as shown, and the upper end of the inner conductor is adapted for connection to a hose pipe so that air, oil, or other insulating fluid may be circulated through the conductors. Fig. 2 shows a modified construction in which water may be used as the cooling fluid. The inner conductor consists of coaxial metal tubes 28, 29 connected together at their ends, as shown, and communicating with each other through apertures 31 in the tube 28 so that cooling water may be passed through the tube 28 into the space between the two tubes and discharged through an aperture 30 in the tube 29. The outer conductor comprises a tube 33 provided with apertures 45 and jacketed by inner and outer tubes 32, 34 through which water is circulated. In this construction the outer conductor is not insulated from the casing 1. In modified constructions of the form shown in Fig. 2, the outer tube of the inner conductor and the inner jacketing tube of the outer conductor are replaced by a single insulating tube, or one of these tubes is replaced by an insulating covering on the other. Specifications 144,191, [Class 38 (i)], 187,027, [Class 38 (v)], 413,698, and 414,054 are referred to.