久久黄色国产精品一区视频,日本高清一级二级三级,少妇下面好爽好紧好湿一区二区,精品人妖一区二区三区四区,一二三四五区av蜜桃,人妻一区二区三区av,男女真人后进式猛烈视频网站,日本不卡在线视频二区三区,91九色免费视频网站,国精产品一区一区三区有限在线

common problem

What should we pay attention to when choosing cable machinery

author:admintime:2019-09-22 22:12click:
            When choosing wire and cable, attention should be paid to the selection of wire and cable types and specifications (conductor cross section).
            1. Selection of Wire and Cable Types            When choosing wires and cables, consideration should be given to their use, laying conditions and safety.
            According to different uses, power cables, overhead insulated cables and control cables can be selected.
            According to different laying conditions, general plastic insulated cables, steel tape armoured cables, steel wire armoured cables and anti-corrosion cables can be selected.
            According to safety requirements, non-flammable cable, flame-retardant cable, halogen-free flame-retardant cable, fire-resistant cable and so on can be selected.
            2. Selection of wire and cable specifications 
           When determining the specifications of wires and cables (conductor cross section), the selection conditions such as heating, voltage loss, economic current density and mechanical strength should generally be considered. According to experience, low-voltage power line usually chooses section according to heating condition because of its large load current, and then checks its voltage loss and mechanical strength; low-voltage lighting line, because of its high requirement for voltage level, can choose section according to the allowable voltage loss condition first, then checks its heating condition and mechanical strength; and high-voltage power line, because of its high requirement for voltage level, can choose section according to the allowable voltage loss condition. First, the section is selected according to the economic current density, then the heating condition and the allowable voltage loss of the cable machinery are checked, and the mechanical strength of the high voltage overhead lines should also be checked. If the user has no experience, he should consult the relevant professional units or
            Personal opinion.
            Explanation: 1. The current carrying capacity of the same specification aluminium-core conductor is about 0.7 times that of the copper-core conductor. The aluminium-core conductor is larger than the copper-core conductor, the crosslinked polyethylene insulator is smaller, and the refractory wire and cable is larger.
            3. The calculation capacity of this table is based on three-phase 380V and Cos_ phi=0.85. If single-phase 220V and Cos_ phi=0.85, the capacity should be *1/3.
            4. When the ambient temperature is high or the open application mode is adopted, the safe current carrying capacity will decrease. At this time, larger specifications should be selected; when used for frequent starting motor, larger 2-3 specifications should be selected.
            5. The PVC insulated wires in this table are calculated by single overhead laying method. If they are for pipe-piercing or multi-laying, 2-3 specifications should be selected.
            6. The above data are for reference only. The final design and determination of cable types and specifications should refer to relevant professional information or electrical manuals.
            Normal, and according to the cable type specifications, length and ambient temperature, the measurement results are corrected appropriately. Small size (solid conductor below 10mm 2) cables should also be measured whether conductors are on or off.
            6. When laying cables directly, attention should be paid to soil conditions. The depth of laying cables under general buildings is not less than 0.3 meters, and the surrounding environment is more complex, such as arable land, construction sites or roads, etc. A certain depth of laying (0.7-1 meters) should be required to prevent accidental damage to the buried cables. When necessary, the cables should be erected clearly. A marked sign.

Telephone

0769-85415700

function

Price

quality

service

Wechat sweep

Mobile phone sweep

国产精品成人国产乱| 中文字幕日韩熟女av| 欧洲-级毛片内射| 国产免费又色又爽又黄软件| 波多野吉衣av无码| 亚洲成人小说| 国产精品厕所| 国产传媒剧情久久久av| 五月天亚洲av优女天堂| 91精品国产综合久久久蜜臀九色| av免费网站不卡观看| 一区二区三区在线乱码| 精品人妻一区二区三区狼人| 一区二区三区四区亚洲免费 | 国内自拍偷拍一区二区| 国产一级一片内射视频在线| 亚洲二区精品婷婷久久精品| 懂色av一区二区三区网久久| 国产精品女主播在线播放| 日韩有码在线观看视频| 国产精品久久免费中文字幕| 国产人妻高清国产拍精品| 国产成人精品日本亚洲专区61| 日韩精品视频一区二区三区| 一区二区三区乱码在线 | 欧洲| 伊人久久久精品区aaa片| 97精品国产手机| 中文亚洲av片在线观看不卡| 婷婷一区二区三区在线| 亚洲中国美女精品久久久 | 日韩在线精品视频免费| 日本超骚少妇熟妇视频| 国产高清在线精品一区二区三区 | 久久国内精品自在自线图片 | 成人性生交大全免费看| 视频在线国产一区二区| 久久影院午夜理论片无码| 大地资源网高清在线播放| 日夜啪啪一区二区三区| 日韩精品无码av中文无码版| 中文字幕有码一区二区三区|