Electricity: conductors and insulators – With fluids or vacuum – With cooling or fluid feeding – circulating or distributing
Patent
1982-09-07
1984-10-23
Braun, Fred L.
Electricity: conductors and insulators
With fluids or vacuum
With cooling or fluid feeding, circulating or distributing
174 15C, 2191379, H01B 734
Patent
active
044790295
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to electrical engineering and, more particularly, to electric cables, namely, bipolar flexible water-cooled cables.
DESCRIPTION OF THE PRIOR ART
At present, transformers are normally connected to welding guns by means of bipolar flexible water-cooled cables of the type in which the go (positive) and return conductors are placed in a common hose; they alternate in the direction of the current and are insulated from each other by a profiled rubber sheath (cf., "Welding Reference Book", ed. by S. V. Sokolov, vol. 1, Moscow, 1961, p. 368).
Cables of this type suffer from fast wear of the conductors due to electrodynamic shocks. This disadvantage is partially eliminated in a cable produced by the British "Huddon" company.
A bipolar flexible water-cooled cable, produced by Huddon, comprises go (positive) and return water-cooled conductors which are placed in a common hose, alternate in the direction of the current and are insulated from each other by a profiled sheath; the go and return conductors are stranded at a pitch of 300 mm.
In the latter type of cable, electrodynamic shocks are reduced or countered by directing current to three separate alternating conductors and by reducing the electrodynamic interaction length from 2,500 mm to 300 mm, which, in turn, is attained by stranding the conductors at a pitch of 300 mm.
However, the use of three alternating conductors in which current flows in different directions and the reduction of the length over which the conductors interact with one another do not fully eliminate electrodynamic shocks, because the go and return conductors in the Huddon cable are parallel; it must be borne in mind that electrodynamic forces grow weaker if the go and return conductors intersect. The dynamic characteristics of a cable can be improved by increasing the number of conductors, but this leads to a very complicated cable design; on the other hand, it is impossible to reduce the stranding pitch because of plastic deformation of the conductors. In the cable under review, electrodynamic shocks account for rapid wear of the conductors throughout the cable length; the wear is the strongest at points where the conductors are coupled to welding connectors. In welding connectors, the radial electrodynamic forces produce a tangential component which breaks the cable conductors in immediate proximity to the welding connector. Besides, the conductor stranding and cable assembly conditions are such that the dielectric sheath can only be 1 mm thick; abrasion, bending and heat lead to fast wear of such a thin sheath, wherefore conductors of different polarity may be shorted at any point along the cable.
The stranding of the positive and negative polarity conductors in combination with the insulating sheath and neutral conductor is a complicated process that has to be done by highly skilled operators, keeping in mind that the final stage of the stranding operation is carried out manually. The most important thing is to ensure normal stranding of the conductors. If the strand pitch is greater than 300 mm, the conductors of different polarities are brought together during the initial two days of operation, the conductors of different polarities no longer alternate, and electrodynamic shocks gain in strength. The cable starts "dancing" in the hands of the operator, a single workshift is enough to put such a cable out of operation. A strand pitch of less than 300 mm seriously affects the cooling of the conductors placed in the shaped insulating sheath, because the conductors are firmly pressed together and there is not enough space for the passage of cooling water. The resultant overheating renders the cable inoperative.
SUMMARY OF THE INVENTION
The present invention essentially aims at providing a bipolar flexible water-cooled cable design which would minimize electrodynamic shocks, while ensuring excellent electrical characteristics of the cable.
The invention provides a bipolar flexible water-cooled cable comprising a go (positive) condu
REFERENCES:
patent: 3596786 (1971-08-01), Bernard
patent: 3801724 (1974-04-01), Goodman
patent: 3808350 (1974-04-01), Kluge et al.
patent: 3917898 (1975-11-01), Iketani et al.
patent: 4310718 (1982-01-01), Eng
Welding Reference Book, Ed. by E. V. Sokolov, vol. 1.
Banov Mikhail D.
Chernyshev Alexandr N.
Oshkin Anatoly I.
Braun Fred L.
Nimmo Morris H.
Toliyattinsky Politekhnichesky Institut
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