Showing papers on "Pressboard published in 1980"

Cable sleeve liner and heat recoverable cable splice case incorporating the liner

Abstract: A liner (1) for a heat-recoverable sleeve of a cable splice is of laminate construction with at least one layer (23, 24) of fibrous pressboard disposed between a metal, moisture-impermeable layer (21) and a microperforated polymeric Mylar layer (25). The liner (1) is sufficiently rigid to support the recovered sleeve, but is foldable about longitudinal creases (10) for wrapping around the splice.

Surge voltage arrester - with gas duct in insulated tube parallel to nonlinear resistor stack

Abstract: Surge voltage arrester consists of at least one stack of nonlinear resistors which are enclosed in heat conductive insulating material. A duct for the discharge of gas parallel to the stack is a bush, made of insulating material such as laminated pressboard, which is also enclosed by the insulating material and has openings in its wall, closed by an insulating foil, such as heat shrinkage polyethylene. The pref. insulating material is a mixt. of porcelain chips and fine alumina particles, inside a ribbed porcelain tube. This prevents any direct contact of a short-circuit arc and of hot gases with the inside of the housing.

Short Circuit Vibration Analysis of a Shell Form Power Transformer

Abstract: The short-circuit axial vibration of a 250 Mva 500 kV single phase shell form transformer is calculated. The displacements of the coils and the stresses on the pressboard insulation between the coils are found for various design and operating conditions. Three different lumped mass models with nonlinear press-board representation are used for calculating the vibration in various parts of the coils because the frame which backs up the coils during short circuit is nonuniform. In shell form transformers manufactured by the authors' company the frame consists of both the core and the tank which have considerably different mechanical impedances. These impedances are shown to be quite important and methods for evaluating them are given. The impedance of the tank is determined from the results of tests of a 1/7 scale model. The results show that dynamic effects are not large. The maximum calculated pressboard stress is 2290 psi (15790 kPa), which is only 27% higher than the statically calculated stress; and the maximum calculated coil displacement is .87 inch (2.21 cm). It is also found that friction in the interleaved core joints is sufficient to prevent core separation.

Laminated pressboard mfr. - with several loading and unloading stations from supply conveyor to parallel auxiliary conveyors

Abstract: The loading and unloading station for a flow line prodn of laminated pressboard sheets has on the feeder conveyor track at >=1(pref-2) stations for loading as well as for unloading. These discharge the sheets to >=2 parallel auxiliary conveyor tracks. The sheets are transported on the auxiliary conveyor tracks intermittently and in synchronism with the conveyor plates to and from the press stations. Arrangement facilitates the mfr. of smaller batches of different specification. The number of sets in circulation at any given time (and therefore the invested capital) can be kept low.

Foot support insole - with specified layers of leather, plastic foam and cork pressboard

Abstract: An insole for shoes to support the metatarsus is made from a last to suit the individual requirements. The layer nearest the foot is made of a material which can breathe, e.g. suede, supported by a layer of fibre-reinforced plastic. A cushion pref. made of crosslinked polyethylene foam follows, resting on a layer of cork pressboard. The whole is enclosed at the bottom by a sheet of EV-material and another layer of cork pressboard. If the central metatarsus bone needs supports, another pad of crosslinked polyethylene foam is arranged at the sport concerned. Simple and low-cost method produce an insole which combines the support needed with freedom for the foot muscles.

Electrical insulation e.g. of pressboard type contains boron - to improve and stabilise loss tangent and resistivity

Abstract: Cellulose-based electrical insulation (of the presspahn or pressboard type) contains 0.02-1.1 wt.% B w.r.t. abs. dry matter. Incorporation of B improves the tan delta and electrical resistivity values and stabilises them during operation. B is pref. added in the form of boric acid (in aq. or aq.-alcoholic soln.) or a B cpd. forming boric acid on reaction with water, e.g. boric oxide or triethylborate (in alcoholic soln.). It can be added during pulp prepn., before pressing or before drying.