变频调速分级恒压灌溉自动控制系统及应用

为解决机电泵利用工频电源(50 Hz)作恒速运转条件下,灌溉面积或地形高差变化较大的管道式喷微灌系统灌水均匀度不能满足灌溉要求的问题,提出了一种变频调速分级恒压灌溉自动控制系统,该系统将变频技术和自动化技术相结合,具有变频调速和全自动闭环控制功能的机电一体化智能设备,可同时对1台或多台三相380 V,50 Hz水泵电动机进行自动控制.该系统设计了多段压力设置转换电路,可根据预先设定的压力控制值自动进行压力等级切换,并对管网的电磁阀开启、关闭进行控制,实现分级恒压自动供水灌溉.通过工程实例分析表明,采用水泵工频控制时喷灌系统水头最大差值为12.89 m,采用变频分级恒压控制时喷灌系统水头最大差值为3.38 m,满足设计压力变幅不大于4.00 m的要求.同时该系统具有节水、节能、自动化程度高、运行管理方便以及保证管网和水泵安全运行等功能,能够根据灌溉分区进行分级恒压自动供水灌溉,满足灌水均匀度要求.

Variable frequency and adjustable constant pressure automatic control irrigation system and its application

In a sprinkler irrigation system with long pipe, there is a constant frequency(50 Hz)motor to derive the pump for delivering water. If the irrigating area or elevation change greatly in an irrigation field, the sprinkler irrigation uniformity will become unsatisfactory. In order to solve this problem, a variable frequency and adjustable constant pressure automatic control irrigation system is proposed. In the system, frequency conversion and automation technique are combined, and it is a kind of mechatronic-intelligent device with variable frequency motor and closed-loop fully automatic control function, and it can control for one or more AC 380 V, 50 Hz pump motors automatically at the same time. An electrical circuit is designed for setting different constant pressure levels. As a result, the system can vary the pressure in a pipe network automatically according to the pressure levels prescribed, by opening and closing the electromagnetic valves installed in the network; eventually, an automatically adjustable constant pressure water supply irrigation process is realized. Through the analysis of an engineering project, it is shown that the maximum difference in sprinkler system head is 12.89 m while the pump operating at 50 Hz, by using variable frequency adjustable constant pressure control system, however, the maximum difference in the sprinkler head is 3.38 m, which has met the requirement on pressure variation. Also, this system has a few advantages, such as water saving, energy saving, high degree of automation, convenient operation and management, guaranteed safe operation of pipe network and pump. It allows a pump to supply water to the sprinkler under a prescribed pressure level according to an irrigation field partition, thus the irrigation uniformity of sprinkler is favourable and satisfactory.