Pressboard

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

Moulded hot press

Abstract: The utility model is a molding hot press, which comprises a doorframe, a delivery mechanism, a lower pressboard, an upper pressboard and an oil pressure elevating system, as well as a guide pole and a guide plate. The delivery mechanism is comprised of a guide way, a guide fixing frame and a moving platen; the guide pole is arranged between the homolateral doorframes; a side of the guide plate is positioned on the lower pressboard, while the other side slides in concert with the guide plate lateral wall. Meanwhile, the guide is positioned on the guide plate and the homolateral guides between two guide plates can be positioned on the guide pole. Moreover, because the guide fixing frame is adopted, the vibration when the moving platen feeds is reduced and the mechanical deformation of the lower pressboard subject to repeated pressing of a workpiece and the moving platen is eliminated. Furthermore, through the guide plate and the guide pole, the deviation can be reduced when the lower pressboard is working, so as to not only improve the product quality, but also greatly promote work efficiency and even relieve labor strength of operators.

Positive streamer characteristic at the interface of TiO 2 nanofluid/pressboard under lightning impulse voltage

Abstract: Recent studies have found that the creeping flashover strength of oil-impregnated pressboard can be improved by the modification of nanoparticles. To further explore the modification effect of nanoparticles, this paper studied the effect of TiO 2 nanoparticles on the creeping flashover strength of transformer oil-impregnated pressboard and its prebreakdown streamer characteristics under positive lightning impulse voltage. The test results indicate that the creeping flashover voltage is increased by 34.6% with the addition of TiO 2 nanoparticles. Furthermore, positive streamer characteristic at the interface of nanofluid/pressboard including shape, propagation length and velocity was greatly changed in the presence of nanoparticles. Streamers at the interface of pure oil/pressboard tend to propagate closely along the pressboard surface with a rapidly increased length. Whereas streamers at the interface of nanofluid/pressboard have more lateral branches extending into the surrounding oil and develop with a much shorter length. This demonstrates that the propagation of positive streamers is dramatically restrained by the addition of TiO 2 nanoparticles, resulting in the increase of creeping flashover strength.

Electrical discharge analysis on nanofluid/pressboard surface under AC voltage application

Abstract: Electrical discharge on pressboard surface is one of the major failure mechanisms in power transformer. This study aims to analyze the effect of nanofluid on the electrical discharge at the surface of pressboard material used in power transformers under AC application. A needle to plane configuration with constant gap length was implemented on the surface of pressboard. First, the value and polarity of applied AC voltage during electrical discharge was measured in base transformer oil. Then, alumina nanoparticles were added with different weight fractions. The discharge behavior in nanofluids was obtained and compared with that of base oil. Discharge magnitudes for all nanofluid samples were better than that of base oil. The results were discussed in terms of surface charging of nanoparticles and its role in discharging phenomenon on nanofluid/pressboard surface.

Pre-Breakdown Streamer Propagation and Positive Lightning Breakdown Characteristics of Palm Oil Impregnated Aged Pressboard

Abstract: This paper presents the investigation on the breakdown characteristics and pre-breakdown streamer propagation of Palm Oil (PO) impregnated aged pressboard under positive lightning impulse voltages. The experimental work was carried out under a non-uniform field with needle-plane electrodes configuration. The streamer stopping length and breakdown voltage of 2 types of refined, bleached, and deodorized palm oil were examined in the presence of new and aged pressboards. The pressboard was placed in parallel to the needle-plane electrode at a gap distance of 50 mm. The lightning breakdown voltage was applied to the samples based on 1 shot per step rising voltage method under positive polarity as per IEC 60897. The presence of impregnated pressboard in both PO slightly increases the 50% positive lightning breakdown voltages. PO impregnated pressboards have lower 50% positive lightning breakdown voltages than MO. After subjected to ageing, the positive lightning breakdown voltages for PO and MO impregnated pressboards decrease. In the presence of aged pressboard, the streamers in PO generally propagate further than MO at the same voltage level.

Plate type polishing device

Abstract: The utility model relates to a hand grinding and polishing tool featured in non rotary polishing, which comprises a flat type grinding plate with a handle, grinding and polishing materials coated on the grinding plate surface, and an active pressboard mechanism used to fix the grinding and polishing materials on the pressed grinding plate surface. The pressboard mechanism is composed of a pressboard, a spring, and a pin, and the pressboard mechanism is in active connection with the grinding plate. According to the lever principle, a sand cloth pressed on the grinding plate surface flatly and turned over is fixed and pressed tightly or loosened for changing. The utility model has the advantages of simple structure, labor saving, and high usage and convenient changing of the sand cloth.