Agricultural production line in the People's Daily life， and often need to some parameters， such as the air-conditioning system to control the temperature， water system， ventilation system of air pressure， the system with ac motor is most of the Due to the motor speed cannot before， in order to achieve convenient adjustment to the physical control， people had to using some simple methods， such as by regulating valves， air pressure to adjust the flow in the system， which not only such reach good adjustment effect， and large amounts of energy is wasted baffle and According to statistics， China's current use of fans and pumps about 25% of energy consumption is Therefore， the state economic and trade commission in 1994 issued 763 files on strengthening the energy-saving reconstruct fans and pumps， encourage and support in frequency energy-saving technical In addition， according to the characteristics of ac motor， to realize the continuous smooth speed adjustment， the best method is to use frequency conversion governor， is the standard of alternating current， voltage variable frequency converted the ac motor， supply and can adjust to ChengJinHang motor Using frequency converter for energy saving transformation of fans and pumps， not only avoid due to adopt baffle or valve caused power waste， but also will greatly enhance the accuracy and adjusting control， we can really convenient to achieve an air conditioning system and the temperature constant pressure water supply 来源于希望对你有所帮助
序言的英文：preface ['prefis] (书籍、演讲等的)序言，前言，绪言，引语，开场白introduction [，intrə'dʌkʃən] 前言，引言，序言；导论；(音乐的)序曲foreword ['fɔ:wə:d] (文章、杂志等的)序，序言，序文，前言，绪言，同近义词: introduction; perface英文preface、foreword都含“书的正式篇章开始之前的一段文字”的意思。preface 指“由书的作者或他人为该书写的序言或序文，它是与本书分开的一部分，用来解释写书的目的、重要性等，篇幅一般比foreward长”。 如:This book has a preface written by the 这本书有作者写的序言。foreword 指“书的简短的序文”， 如:That book has a preface， not a 那本书有序文， 没有前言。参考例句： The preface to this book is on the preceding page 前边一页是这本书的序言。 To preface a Book By a life of the writer 以作者的生平作为一本书的序言 In her preface she pours out vials of wrath on her 在序言里她对她的诽谤者表示愤慨。 This Book has a preface written By the 这本书有作者写的序言。 This foreword of the book is writed by a famouse writer 这本书的序言是由一个著名作家写的。 The preface is complete in 这前言本身就是完整的。 The accident was the preface to a great scientific 这一偶然事件成了一项重大科学发现的开端。 Can you please preface my book? 你能给我这本书作序吗？ The preface of the book includes an account of the author's 该书前言记述了作者生平。 Jame's prefaces are always important 詹姆斯小说的前言总是重要的。 The introduction explains how the chapters are organized 前言部分说明各章的怎样组织。 In his preface hawthorne seeks to explain the attraction that italy has for the writers of romances 霍桑在前言中试图阐明意大利对传奇作家的吸引力。
Line in the industrial and agricultural production of people's daily lives， often need to control a number of physical quantities， such as the temperature of air-conditioning systems， water supply system， water pressure， ventilation system， air flow and so on， the vast majority of these systems is to use AC motor drive Previously due to the motor speed can not be easily adjusted in order to achieve the above-mentioned physical quantities of control， people have to use some simple methods， such as adjustable air volume with the bumpers， with valves to regulate flow and pressure， resulting in these systems not only from a very good adjustment effects， but also a lot of power tailgate and valves have been According to statistics，China's current use of fans， pumps about 25% of the energy is unnecessarily Thus， the State Economic and Trade Commission in 1994 issued a 763 Nianxia document "on the strengthening of fans， pumps energy-saving advice，" encourage and support energy-saving inverter technology in promoting the use of all walks of In addition， according to the characteristics of AC motor to achieve smooth， continuous speed control， the best way is to use frequency converter， frequency converter is to convert the standard AC frequency， variable voltage alternating current， the supply of electrical motors and can speed into the device to With frequency inverter fans， water pumpsEnergy-saving， not only to avoid the use of baffles or valves due to a result of energy wasted， but also greatly improve the precision of the control and regulation， we can easily achieve a real system and the constant pressure constant temperature air conditioning and water
