Pressboard

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

Partial Discharge Phenomena in Converter and Traction Transformers: Identification and Reliability

Abstract: After the development of power electronics converters, the number of transformers subjected to non-sinusoidal stresses (including DC) has increased in applications such as HVDC links and traction (electric train power cars). The effects of non-sinusoidal voltages on transformer insulation have been investigated by many researchers, but still now, there are some issues that must be understood. Some of those issues are tackled in this Thesis, studying PD phenomena behavior in Kraft paper, pressboard and mineral oil at different voltage conditions like AC, DC, AC+DC, notched AC and square waveforms. From the point of view of converter transformers, it was found that the combined effect of AC and DC voltages produces higher stresses in the pressboard that those that are present under pure DC voltages. The electrical conductivity of the dielectric systems in DC and AC+DC conditions has demonstrated to be a critical parameter, so, its measurement and analysis was also taken into account during all the experiments. Regarding notched voltages, the RMS reduction caused by notches (depending on firing and overlap angles) seems to increase the PDIV. However, the experimental results show that once PD activity has incepted, the notches increase PD repetition rate and magnitude, producing a higher degradation rate of paper. On the other hand, the reduction of mineral oil stocks, their relatively low flash point as well as environmental issues, are factors that are pushing towards the use of esters as transformer insulating fluids. This PhD Thesis also covers the study of two different esters with the scope to validate their use in traction transformers. Mineral oil was used as benchmark. The complete set of dielectric tests performed in the three fluids, show that esters behave better than mineral oil in practically all the investigated conditions, so, their application in traction transformers is possible and encouraged.

DC characterization of isoparaffinic insulation oil

Abstract: Converter transformers in HVDC stations are subject to both AC and DC stresses. With new oils entering the market it is important that these are characterized both for AC and DC. This paper focuses on DC characterization of one such oil, which is an isoparaffinic oil produced using a gas to liquid production process. The results are compared to mineral oil as reference. The isoparaffinic oil is shown to have a very high resistivity. In fact, the resistivity is so high that it is more resistive than impregnated pressboard with low moisture content. This is a dielectric risk which must be considered if the oil is to be used in converter transformers.

Combined material cell phone case's exhausted formula molding device

Abstract: The utility model relates to a molding device technical field refers in particular to combined material cell phone case's exhausted formula molding device, including the die, the terrace die, go up the hot pressboard, lower hot pressboard, a temperature controller, a weighing sensor and a temperature sensor, the cavity has been offered at the middle part of terminal surface under the die, terrace die up end middle part is equipped with the boss to the epirelief, enclose each other between the boss of terrace die and the cavity of die and close the formation die cavity, temperature sensor stretches into in the die cavity, upward be equipped with the heating pipe in the hot pressboard, be equipped with down the heating pipe down in the hot pressboard, the surface of cavity and boss all forms one deck graphite alkene nanometer film, air discharge duct a plurality of and the cavity intercommunication is offered to the terminal surface under the die, a plurality of air discharge ducts center on the cavity, the utility model discloses utilize the air discharge duct, can exhaust in die?heating pressure processes, glue the gas and the gas between material and the mould that mix with between the thick material through the messenger that exerts pressure and outwards discharge from the air discharge duct, improve product quality.

Press board lamination article for oillfilled electric apparatus

Abstract: PURPOSE:To provide a pressboard lamination article, which is used for oil-filled transformers, power capacitors, reactors, oil-filled tank type circuit breakers and so forth, and also which permits ready automation of its manufacture and does not need a hot oil dry process.