Pressboard

About: Pressboard is a research topic. Over the lifetime, 1123 publications have been published within this topic receiving 9089 citations.

Cooling device for industrial belt hot-press

Abstract: The invention relates to a cooling device for an industrial belt hot-press, which comprises a hot pressboard with cooling function. The hot pressboard is provided with pore passage which is manufactured in a heating plate; the pore passage is a structure which is parallel to the upper plane and the lower plane of the hot-press board and is manufactured along the vertical direction in a board bodyof the hot pressboard; and a cooling medium can directly pass through the pore passage to realize the cooling of the hot pressboard. The cooling device has high cooling efficiency with the effect improved by over 80 percent compared with the prior cooling device, has a small volume without assembly positioning problem, works stably without water leakage problem, and has no restriction on the length of the hot pressboard.

Light emission study in transformer oil and along oil/cellulose interface using a spark-gap system

Abstract: Interfaces between oil and oil-impregnated-pressboard are known to weaken insulation system strength. The work here describes differences in the observed discharges in transformer oils and along oil/oil-impregnated-pressboard interfaces. Oil breakdown in a uniform electric field was initiated by triggering a spark gap either at the anode or at the cathode using a liquid trigatron. Light emission during the breakdown processes was detected using a photomultiplier tube. Breakdown voltage, time to breakdown, streamer propagation speed and polarity effect were seen to differ in a transformer oil and along an oil/oil-impregnated pressboard interface.

Capacitance change during the aging of a combined system of a solid-liquid dielectric under switching impulse voltages

Abstract: This paper presents the result of an experimental investigation of the arising non-linear phenomena in bakelite and phenol impregnated pressboard specimens (pertinax), immersed in insulating oil, under the application of high voltage impulses. For this purpose, bakelite and pertinax samples were electrically stressed with 250/2500 /spl mu/s switching impulse voltages through a tip-plane electrode assembly. The total electric charge flow through the specimens and the overall capacitance C of the metal tip-solid dielectric-metal plane combination were measured in the high-field regime, the experimental results show an exponential increase of the overall capacitance which may be attributed to the excessive charge flow due to the electron avalanche effect. The aforementioned capacitance involved with the partial discharges depends on the environment temperature (partial discharges enhanced by temperature). Further theoretical consideration leads to a mathematical model which gives an expression for C. The theoretical expectations on the basis of this model are found to be in good agreement with the obtained experimental results.

Effect of DC bias on surface strength of processed pressboard under lightning and switching impulses

Abstract: The surface strength of processed transformer pressboard is determined in a practical configuration under additive polarity composite DC plus switching impulse and DC plus lightning impulse voltages. Results obtained with specimens impregnated with field-aged oil are presented. With both types of composite voltage, most breakdowns occurred in the oil away from the interface. There is no significant influence of gap length on the location of the breakdown. With increasing DC bias fewer breakdowns occurred on the surface. >