根據(jù)電機學原理，交流異步電動機轉(zhuǎn)速由下式確定:
節(jié)能原理,高壓變頻器
節(jié)能原理,高壓變頻器
由式(1)可知，電動機的輸出轉(zhuǎn)速與輸入的電源頻率、轉(zhuǎn)差率、電機的極對數(shù)有關，改變極對數(shù)的成為變極調(diào)速，此種調(diào)速屬于有極調(diào)速，調(diào)速不平滑，主要用于不需要頻繁變速的地方。改變電機轉(zhuǎn)差率的調(diào)速方式有：調(diào)壓調(diào)速，電磁調(diào)速，繞線式電機轉(zhuǎn)子串電阻調(diào)速，該種調(diào)速需要產(chǎn)生新的轉(zhuǎn)差率，消耗轉(zhuǎn)差功率，屬于低效調(diào)速。而通過改變電機的輸入頻率的變頻調(diào)速，近似無級調(diào)速，是高效不耗能的調(diào)速方式，也是現(xiàn)在應用最廣泛的一種調(diào)速方式。
2.2 高壓變頻器節(jié)能原理
根據(jù)流體力學的基本定律可知：風機(或水泵)類設備均屬平方轉(zhuǎn)矩負載，其轉(zhuǎn)速n與流量Q、壓力(揚程)H以及軸功率P具有如下關系：
節(jié)能原理,高壓變頻器
節(jié)能原理,高壓變頻器
由公式(2)、(3)、(4)可知，風機(或水泵)的流量與其轉(zhuǎn)速成正比，壓力(或揚程)與其轉(zhuǎn)速的平方成正比，軸功率與其轉(zhuǎn)速的立方成正比。當風機轉(zhuǎn)速降低后，其軸功率隨轉(zhuǎn)速的三次方降低，驅(qū)動風機的電機所需的電功率亦可相應降低。因此調(diào)節(jié)轉(zhuǎn)速是風機節(jié)能的重要途徑。
3、高壓變頻調(diào)速系統(tǒng)應用情況
3.1 高壓變頻器的組成
森蘭SBH系列高壓變頻器采用單元串聯(lián)多電平技術，采用多個低壓變頻功率單元串聯(lián)的方式實現(xiàn)直接高壓輸出，屬于“高-高“電壓源型變頻器，該變頻器具有對電網(wǎng)諧波污染小，輸入功率因數(shù)高，不必采用輸入諧波濾波器和功率因數(shù)補償裝置，滿足IEEE519-1992國際標準和GB/T14549-93國家標準對輸入諧波的要求。輸出波形質(zhì)量好，不存在諧波引起的電機附加發(fā)熱和轉(zhuǎn)矩脈動、噪音、共模電壓等問題，不必設置輸出濾波器，可直接拖動普通的異步電機。
其原理框圖如圖1 所示：
節(jié)能原理,高壓變頻器
節(jié)能原理,高壓變頻器is in line with the strategic goal of Jintuo company to create high-end reflow welding, comparable to imported similar equipment and create a new brand.
Second, after-sales service
As a new generation controller just launched by Siemens, the development and use environment of this product is indeed very different from that of the original small PLC S7 200, but Siemens' question and answer, powerful and perfect technical service mode has strengthened its determination to choose S7 1200.
Third, product performance
If good brand image and high-quality after-sales service are the indispensable reasons that affect my choice of s7-1200, whether s7-1200 can meet the application requirements of this project is the final factor to determine the choice of s7-1200. At least the following characteristics of s7-1200 are one of the main factors I consider.
The friendly development environment provides good conditions for developing complex and high-quality programs.
The quality of the control procedure of a project or a piece of equipment depends on whether the maintainability of the procedure is good. Program
