单片机自动控制无功功率补偿的应用

许多用电设备正常运行时，能够产生大量的滞后电流而引起用电系统功率因数的大幅度下降，从而增加了电能损耗。以兴隆林业局贮木加工厂为例，１９９７年１月份总用电费为６５３６５．３６元，利率罚款为．１３８６９．０２元，占总费用的 ２１％，其原因就是功率因数太低（ｃｏｓ　＝０．５２）。为解决这一问题，必须提高功率因数，进行人工无功功率补偿。 功率因数补偿有三种方式：即①调相机补偿；②同步电动机补偿；③电容器补偿。但①、②两种补偿方式投资大、维修量大。而采用电容器补偿具有有功损耗小、无旋转部分、维护量小、补偿量…     

电力变压器的节能

在很多单位开展的节能工作 中，往往只注重抓用电设备的合理 使用和采取限制非生产用电等措 施，忽略了电力变压器（简称变压 器）的节能。而变压器是一种长期连 续运行的设备，如果能设法提高其 运行效率及功率因数，设计合理的 配电方式，将会有明显的节能效 果。 １提高变压器的运行效率 １．１合理选用变压器的容量及数量 从理论上讲，要使变压器发挥 最大效率，应使平均负荷率为额定 容量的５０％～７５％。但因为变压器 本身的负载及功率因数是变化的， 且有超载运行的可能性，故不必按最大效率的准则来选择变压器的容量。通常工厂及…     

SVG在工厂低压电力系统中的应用

通过对无功补偿装置的介绍,分析了安装该装置的必要性,根据公司供电系统无功补偿现状,提出无功补偿方案,改造后效果分析充分说明了用SVG提高功率因数,可降低系统中的无功功率,可大幅降低线路和变压器的电能损耗,达到节能降耗的目的。     

功率因数在电力系统中的应用

在电力系统中,提高功率因数对于降低电力系统损耗、节约电能、提高供电质量等方面意义重大。文章分析了提高功率因数的原理及影响功率因数的因素,得出了补偿电容容量的计算方法,推导了提高功率因数和降低网损之间的关系,概述了提高功率因数所带来的经济效益和社会效益。     

先进的节能(电)技术

河北恒达能源科技有限公司研发的节电系统有照明、路灯、中央空调、风机水泵节电系统等六个系列,适用于很多场合。照明节电系统是一种电磁平衡式外加系统净化和补偿功能节电器,通过提高电路系统的功率因数,调节电路的电压、电流的幅度,降低负载和线路的工     

电子节能灯

电子节能灯该系列电子节能灯具有工作效率高、光线柔和稳定，温度自动补偿，工作安全可靠等特点。其节电效率可达７５％，一只９Ｗ的电子节能灯，发光效率相当于一只４０Ｗ的白炽灯，提高效率近５倍。该灯功率因数≥９５％；总谐波含量≤２８％、三次谐波含量≤１８％；工...     

密封平衡式管道补偿器

密封平衡式管道补偿器专利号：９５２１５０６５管道补偿器是避免由于管道吸收冷热引起轴向位移变形造成管道破坏的补偿设备。随着我国石油、化工、热电、冶金、轻纺、供水、集中供热等行业迅速发展，在热力管道敷设中补偿器已逐步替代传统Ｕ形弯管。该补偿器适用于热力管...     

波纹管补偿器实际应用中应注意的问题

波纹管补偿器的失效主要有腐蚀泄漏和失稳两种形式.通过正确地选择波纹管制作材料和结构、合理设计波形参数和疲劳寿命、保证安装质量等措施,可提高波纹管补偿器的安全可靠性.     

工厂供电系统无功补偿问题研究

主要对工厂供电系统无功补偿问题进行研究分析,以及利用无功补偿来提高工厂供电系统功率因数的方法和途径。设法提高供电系统的功率因数以提高电能质量,保证供电可靠性,实现工厂供电系统的高效节能运行,提高工厂的综合生产效率和经济性。     

企业供电网络的无功补偿

近年来，由于工农业生产及家用电器用电量的迅速增长，供用电之间的矛盾日趋突出。如何提高供电能力，节约电能，是当前研究的一个重要课题。而企业采取无功负荷补偿，提高功率因数的方法，则可以降低电力网的损耗，是节约电能的一项重要技术措施。     

Browsing Damage on Pine (Pinus sylvestris and P. contorta) by a migrating moose (Alces alces) Population in Winter: Relation to Habitat Composition and Road Barriers

In Scandinavia, moose (Alces alces L.) sometimes cause severe browsing damage to economically-important pine. Moose-vehicle accidents have spurred construction of fences along roads, and these may interfere with moose migration between summer and winter ranges, or the road alone may be a barrier. If this happens and moose build up along roads, landowners may suffer economically. Therefore, this study investigated whether roads, fences or other factors influence the use of young pine stands by moose. Eighty stands along roads in northern Sweden were evaluated in which individually-browsed branches were counted on 9972 pines. Moose browsing was not significantly related to birch (Betula pendula Roth, B. pubescens Ehrh.) density, nor did it differ between pines (Pinus contorta Douglas or P. sylvestris L.). However, increased pine density, site productivity and proximity to a highway were associated with increased browsing. Further large-scale studies are needed to understand moose habitat selection and the effects of roads.     

Effects of Root Freezing on the Physiology and Growth of Picea glauca,Picea mariana and Pinus banksiana Seedlings Under Different Soil Moisture Regimes

The root systems of 2-yr-old Picea glauca, Picea mariana and Pinus banksiana seedlings were submitted to various frost temperatures during an artificial frost to induce different levels of root damage. Frost-damaged and control seedlings were placed in a greenhouse under high and low soil moisture regimes. Seedling growth and physiology were evaluated periodically. Seedling survival was reduced when root damage reached levels of 60-80%. Root systems of all three species showed partial to total recovery by the end of the experiment. In general, root freezing damage caused reductions in seedling growth, with these reductions becoming less significant over time. Root damage had little to no effect on black spruce and jack pine seedling physiology, while white spruce CO 2 uptake decreased with increasing root damage. Shoot nitrogen content of all three species decreased slightly with increasing root damage.     

Stand Structure in Pine,Spruce and Deciduous Forests: A Comparison Between Finnish and Russian Karelia

This study investigated the stand structure in pine, spruce and deciduous forests in the border district of Finland and Russia. A total of 46 mature forest stands was selected as pairs, the members of each pair being as similar as possible with respect to their forest site type, age, moisture and topography. The stands were then compared between the two countries by means of basal areas and number of stems. The proportions of dominating tree species were 2-12% lower, and correspondingly the proportions of secondary tree species higher, in Russian forests. The density of the forest stock was also higher in each forest type in Russia. The forests in the two countries differed most radically in terms of the abundance of dead trees. The amount was two to four times higher in Russian deciduous and spruce forests, and in pine forests the difference was 10-fold. The stand structures indicated that Russian coniferous stands, in particular, were more heterogeneous than intensively managed pine and spruce stands in Finland.     

Growth and Terminal Bud Formation in Picea abies Seedlings Grown with Alternating Diurnal Temperature and Different Light Qualities

The root collar diameter and the height:diameter ratio are of particular importance in container-grown seedlings where a high density in the containers may produce spindly seedlings. Temperature regimes and light quality are known to affect plant growth. The aim of this study was to identify responses in Picea abies (L.) Karst. seedlings grown with light providing different red:far-red ratios and under temperature regimes with alternating day (DT) and night temperature (NT) from negative (DT < NT) to positive (DT > NT) difference (DIF) between DT and NT. Experiments were conducted in controlled environment chambers and in a daylight phytotron. Only limited thermoperiodic responses appeared in P . abies seedlings with respect to seedling height and dry weight accumulation. The formation of terminal buds, however, was clearly delayed in seedlings grown at negative DIF. The results indicate a requirement for day extension light that is high in far-red, to prevent terminal bud formation under natural short-day conditions. An extended study should be conducted to clarify the minimum level of light intensity and the optimal light quality needed to prevent terminal bud formation under natural short-day conditions.     

CAD与建筑设计的关系

本文分析了CAD在设计中引起的正面和负面影响,并进行了系统的阐述,从而使设计者在应用中能够保持客观的态度。     

Natural Regeneration in Clear-cuts: Effects of Scarification,Slash Removal and Clear-cut Age

The effects of soil scarification (mounding), slash removal and clear-cut age on the natural regeneration in clear-cuts was evaluated using data from four sites in southern Sweden. The treatments were carried out during a good seed and establishment year for birch ( Betula pubescens Ehrh. and B. pendula Roth). Scarification had the strongest positive effect on the density of naturally regenerated seedlings, especially in birch, but also in pine ( Pinus sylvestris L.) and spruce [ Picea abies (L.) Karst]. Slash removal had a positive effect on birch density. No statistically significant effect of clear-cut age was found. In addition, no statistically significant interactions between clear-cut age and scarification or slash removal were found. The ingrowth of field vegetation was the fastest in areas that were not scarified, less rapid in areas scarified on old clear-cuts, and the slowest after scarification in fresh clear-cuts. In conclusion, it may be possible to control the density of birch during a good establishment year for birch. If birch is desired, the best combination of treatments is to remove the slash and scarify; otherwise, these treatments should be avoided.     

Risk Perception Among Non-industrial Private Forest Owners

Based on an enquiry, risk perception among non-industrial private forest owners is described in relation to climate change and forestry hazards. Of the respondents, 11% took action to remedy the effects of climate change. Out of a given set, hazards were ranked according to each respondent's experience of recent substantial financial loss to the estate and in relation to his or her willingness to make investments aimed at risk reduction. For each hazard, the respondent assessed the risk in four classes ranging from very high to negligible risk. Six hazards were considered most problematic in all three aspects: browsing damage, falling timber prices, damage by wind, spruce bark beetle, root rot and pine weevil. A majority of the respondents claimed to take action to reduce the risk associated with at least one hazard, while 35% did not know whether they did. Excluding climate change, the need for decision support was the largest in relation to damage by wind owing to a combination of perceived high risk and a high level of ignorance in relation to whether risk-reducing measures were taken.     

Interactions in decomposition and N mineralization between tropical legume residue components

In situ produced plant residues contain a mixture of different plant components of varying quality. To assess synergistic or antagonistic interactions occurring during the decomposition and mineralization of such mixtures, individual plant parts (stems, leaves, leaf litter and roots) or the mixture of stems, leaves and leaf litter of the agroforestry species pigeonpea (Cajanus cajan) or of crop residues of peanut (Arachis hypogaea) or of the weed hairy indigo (Indigofera hirsuta) were incubated in pots for 19 weeks. Periodically, remaining plant residues were sieved out (>2 mm), weighed and N content as well as soil mineral N determined. Above- and below-ground residues of peanut decomposed fastest and showed the largest N release in agreement with their high N concentration and low-acid detergent fibre (ADF) : N ratio. Hairy indigo was hypothesized to be of lower quality than pigeonpea because of its high-polyphenol content. However, it decomposed faster than pigeonpea, largely because of the higher N and lower lignin concentration of its components. Ranking of individual plant components for N mineralization resulted in the following pattern, leaves > leaf litter > roots > stems. In mixtures of the different plant components a similar species order in decomposition was obtained, e.g. peanut > hairy indigo > pigeonpea. The amount of N released from the mixture was dominated by stem material that comprised 46–61% of the mixture. The interactions in mixtures were relatively small for peanut (generally high-quality components) as well as for pigeonpea (low proportion of high-quality components, i.e. N rich leaf material). However, a positive interaction occurred during later stages of N mineralization in the mixture of hairy indigo as it had a significant proportion of N rich components and absence of highly reactive polyphenols. Thus, for plants with low to intermediate chemical quality attributes, manipulating plant composition (e.g. by varying harvest age, affecting stem and leaf proportions) will be important to obtain significant interactions during decomposition when its components are mixed.     

Pasture production and tree growth in a young pine plantation fertilized with inorganic fertilizers and milk sewage in northwestern Spain

The use of organic waste materials such as milk sewage as an organic fertilizer could have the dual advantages of organic-waste disposal and reduced dependence on inorganic fertilizers. The effects of fertilization with (1) conventional mineral fertilization, (2) milk sewage sludge at 40 kg N ha⁻¹ target rate and (3) no fertilization on pasture production and tree growth were examined in an experiment consisting of two pasture mixtures under a one-year-old Pinus radiata plantation with a density of 2500 trees ha⁻¹. The two pasture mixtures were: (1) Dactylis glomerata L. var. saborto (25 kg ha⁻¹) + Trifolium repens L. group Ladino (4 kg ha⁻¹) + Trifolium pratense L. var. Marino (1 kg ha⁻¹); (2) Lolium perenne L. var. Tove (25 kg ha⁻¹) + Trifolium repens L. group Ladino (4 kg ha⁻¹) + Trifolium pratense L. var. Marino (1 kg ha⁻¹). The experiment began in the spring of 1995 using a randomized block design with three replicates in Castro Riberas de Lea (Lugo, Galicia, north-western Spain). Plot size was 12 × 8 m², with a 1 m buffer strip between plots. Two-year data showed that fertilization with either material had a positive effect on pasture production, with no significant difference between the two fertilization treatments. Tree growth in the milk sewage sludge plot was significantly higher than in the control plots. Inorganic fertilization increased pasture production, but affected tree growth negatively. The results show that milk sewage sludge could be used as a fertilizer in silvo-pastoral systems. This revised version was published online in June 2006 with corrections to the Cover Date.