D:The service life is long, the automaticity is high, does not need the human to safeguard, maintains the quantity to be few.

Above system the effect is remarkable in the actual application, if brings in PLC and the frequency changer the programmer the function integration, potential becomes some special-purpose frequency changers, such system reliability and the toughness big enhancement, the application is simpler, the system total cost also can drop.

May foresee: The future frequency conversion technology will be able to develop to the below direction:

(1) high performance

Thus including internal leveling circuit, the contravariant electric circuit all use the high frequency PWM electric circuit to cause the input, the output all are sine waves; Uses the multi-densification regarding the large capacity frequency changer and many machine is parallel; Reduces frequency changer own loss, the realization high efficiency; Realizes autotune or from the optimization, the remote control and controls far; Even more faces the user, further enhances the workability and Maintainability: Turns towards, the featherweight development small, as well as reduces the cost and so on.

 (2) intellectualization

 Including two aspects: Reduces the hardware as far as possible, realizes the hardware software; Uses the intelligent electric power electronic device and other intellectualized part. The integration is the intellectualized foundation.

 (3) entire digitization

 In recent years, each kind of modern control theory, the expert system, the fuzzy control and the neuron control and so on all were the development hot spots, will cause the electric power electronic control technological development to a brand-new stage. Estimated the 21st century entire numerical control the application will be more widespread thoroughly, even will substitute for the simulation control.

 (4) systematization 

Frequency conversion technology development is inseparable from the development of related technologies, frequency conversion technology development in the 21st century is to grid, regulators, rely machine, electric motors, production machinery and control systems as a whole, from the system for consideration.

变频器在供水控制系统的应用

目前，在水位控制中有很大一部分水泵电机是不变速拖动系统，不变速电机的电能大多消耗在适应供水量的变化而频繁的开停水泵中。这样不但使电机工作在低效区、减短电机的使用寿命，而且电机的频繁开停使设备故障率很高，导致水资源严重浪费，系统的维护、维修工作量较大。

随着高位生活用水和工业用水逐渐增多，传统的控制方法已经落后。原先用人工进行水位控制，由于无法每时每刻对水位进行准确的定位监测，很难准确控制水泵的起停；使用浮标或机械等水位控制装置使供水状况有了一些改变，但由于机械装置的故障多，可靠性差，给维修带来很大的麻烦。

变频技术以其在节能与恒压方面的优越性能可以解决水压控制系统存在的以上问题。考虑选用单片机或PLC与变频器结合为核心构成的系统都能达到较好的控制效果。但在软件设计上，PLC比单片机的编程更简洁、直观；从硬件接口考虑，单片机电路稍微复杂一些；从经济方面考虑，由于PLC工艺的日渐成熟，小型PLC的成本与单片机相差无几，由于要根据现场情况调整系统参数，PLC的软件中时间参数的调整更简单，这样更有利于售后服务人员掌握。基于以上原因，选用了OMRON的 CPM1系列PLC与ABB的变频器作为控制核心，再加上PSW7调节器与WSP300压力变送器，控制效果非常好，软件设计简单，硬件接口简易可行、可靠性高，整个系统的性价比非常高。来!自~优尔论-文|网www.youerw.com 变频器在供水控制系统的应用英文文献和中文翻译(3):http://www.youerw.com/fanyi/lunwen_77942.html