自動化專業(yè)畢業(yè)設(shè)計--plc與變頻器通訊實現(xiàn)自動門變頻調(diào)速

1、<p>　　目 錄 </p><p>　　1.畢業(yè)實踐任務(wù)書----------------------------------------------------------------------2</p><p>　　2.外文翻譯----------------------------------------------------

2、---------------------------3</p><p>　　3.畢業(yè)實踐調(diào)研報告------------------------------------------------------------------16</p><p>　　4.畢業(yè)設(shè)計說明書-----------------------------------------------------------

3、----------18</p><p>　　5.畢業(yè)實踐總結(jié)------------------------------------------------------------------------49</p><p>　　6.參考文獻--------------------------------------------------------------------------

4、----50</p><p><b>　　畢業(yè)設(shè)計任務(wù)書</b></p><p>　　課題名稱 用PLC和變頻器設(shè)計電梯橋箱開關(guān)門的控制系統(tǒng) </p><p><b>　　x </b></p><p>　　課題需要完成的任務(wù)：</p><p>　?。?）選擇PL

5、C和變頻器及感應器和限位開關(guān)等器件構(gòu)建控制系統(tǒng)。</p><p>　?。?）人靠近時，感應器X0為NO，電動機高速開門,碰到開門減速開關(guān)X1時，變?yōu)闇p速開門，碰到開門極限開關(guān)X2時，電機停轉(zhuǎn)。</p><p>　?。?）開始延時，如在0.5秒內(nèi)感應器監(jiān)測到無人，電動機高速關(guān)門，碰到關(guān)門減速開關(guān)X4時，改為低速關(guān)門，碰到關(guān)門極限開關(guān)X5時，電動機停轉(zhuǎn)。</p><p>

6、;　?。?）在關(guān)門期間若感應器監(jiān)測到有人，停止關(guān)門，T1延時0.5秒轉(zhuǎn)換為高速開門。</p><p>　?。?）高速頻率35HZ，低速25HZ，高速時間2S,低速時間4S。</p><p>　?。?）設(shè)計手動操作門的開關(guān)、停止，設(shè)置高峰期頻率</p><p>　?。?）繪制人機界面的操作畫面</p><p>　　通過運行效果寫出結(jié)論。<

7、/p><p><b>　　課題計劃：</b></p><p>　　2.25～3.1 查資料，系統(tǒng)整體方案設(shè)計。</p><p>　　3.1～3.14 硬件系統(tǒng)設(shè)計；控制器設(shè)計。</p><p>　　3.14～3.25 學習使用專用軟件，編制程序。</p><p>　　3.25～4.1

8、 系統(tǒng)調(diào)試，寫畢業(yè)論文。</p><p>　　4.1～4.16 修改、完善畢業(yè)論文，并做答辯準備。</p><p>　　計劃答辯時間：4.22~4.28</p><p>　　自動控制技術(shù)系 系（部、分院） </p><p>　　Key words: electrical automation; Involving related

9、 content; development; applications . </p><p>　　First,Involving related content</p><p>　　Electric Power Systems </p><p>　　An electrical circuit or network is composed of elements s

10、uch as resistors, inductors, and capacitors connected together in some manner. If the network contains no energy sources, such as batteries or electrical generators, it is known as a passive network. On the other hand, i

11、f one or more energy sources are present, the resultant combination is an active network. In studying the behavior of an electrical network, we are interested in determining the voltages and currents that exist within th

12、e </p><p>　　In the case of a resistor, the voltage-current relationship is given by Ohm's law, which states that the voltage across the resistor is equal to the current through the resistor multiplied by

13、 the value of the resistance. Mathematically, this is expressed a</p><p>　　The voltage across a pure inductor is defined by Faraday’s law, which states that the voltage across the inductor is proportional to

14、 the rate of change with time of the current through the inductor. Thus we have</p><p>　　The voltage developed across a capacitor is proportional to the electric charge q accumulating on the plates of the ca

15、pacitor. Since the accumulation of charge may be expressed as the summation, or integral, of the charge increments dq, we have the equation</p><p>　　Active electrical devices involve the conversion of energy

16、 to electrical form. For example, the electrical energy in a battery is derived from its stored chemical energy. The electrical energy of a generator is a result of the mechanical energy of the rotating armature.</p&g

17、t;<p>　　Active electrical elements occur in two basic forms: voltage sources and current sources. In their ideal form, voltage sources generate a constant voltage independent of the current drawn from the source.

18、The aforementioned battery and generator are regarded as voltage sources since their voltage is essentially constant with load. On the other hand, current sources produce a current whose magnitude is independent of the l

19、oad connected to the source. Although current sources are not as familiar i</p><p>　　A common method of analyzing an electrical network is mesh or loop analysis. </p><p>　　The fundamental law th

20、at is applied in this method is Kirchhoff’s first law, which states that the algebraic sum of the voltages around a closed loop is 0, or, in any closed loop, the sum of the voltage rises must equal the sum of the voltage

21、 drops. Mesh analysis consists of assuming that currents-termed loop currents-flow in each loop of a network, algebraically summing the voltage drops around each loop, and setting each sum equal to 0.</p><p>

22、;　　The development of the transformer and AC transmission by L. Gaulard and JD Gibbs of Paris, France, led to AC electric power systems.</p><p>　　In 1889, the first AC transmission line in North America was

23、put into operation in Oregon between Willamette Falls and Portland.</p><p>　　It was a single-phase line transmitting power at 4,000 V over a distance of 21 km. With the development of polyphase systems by Ni

24、kola Tesla, the AC system became even more attractive. By 1888, Tesla held several patents on AC motors, generators, transformers, and transmission systems. Westinghouse bought the patents to these early inventions, and

25、they formed the basis of the present-day AC systems.</p><p>　　In the 1890s, there was considerable controversy over whether the electric utility industry should be standardized on DC or AC. By the turn of th

26、e century, the AC system had won out over the DC system for the following reasons:</p><p>　?。?）Voltage levels can be easily transformed in AC systems, thus providing the flexibility for use of different volt

27、ages for generation, transmission, and consumption.</p><p>　?。?）AC generators are much simpler than DC generators.</p><p>　?。?）AC motors are much simpler and cheaper than DC motors. Therefore, a

28、 normal continuous operation of the power system to provide a reliable power supply to the customers is of paramount importance.</p><p>　　Power system stability may be broadly defined as the property of a po

29、wer system that enables it to remain in a state of operating equilibrium under normal operating conditions and to regain an acceptable state of equilibrium after being subjected to a disturbance.</p><p>　　In

30、stability in a power system may be manifested in many different ways depending on the system configuration and operating mode. </p><p>　　Reducing the harmonic content of the output voltage or current is one

31、of the important tasks of the designers. Harmonics appear as the undesirable noise.Harmonics reduce the power factor. They may excite mechanical resonance at detrimental frequencies or generate acoustical noise in ac mo

32、tor drive </p><p>　　systems.The ripple content (harmonics) is easily reduced by post-filtering after the converter.</p><p>　　The post converter low-pass filter may be designed for cutoff frequen

33、cies that are several times lower than the switching frequency (usually in kilohertz).In the DC-AC inverters,however,the fundamental component of the output voltage or current is either the same as or a simple fraction o

34、f the switching frequency.Hence,an active harmonic reduction strategy is often desirable. Designing an effective low-pass filter with cutoff frequency between the fundamental frequency and the first undesired ha</p>

35、;<p>　　Converter control refers to specifying the desired nominal operating condition and then regulating the converter so that it stays close to the nominal performance in the face of disturbances, noise and mode

36、ling errors. We can analyze the dynamic behavior of the power electronic converter (or local) of the steady-state operating point. The converter operation involves switching modes, therefore an overall converter model is

37、 a nonlinear model. The averaged model, localized to the steady-state oper</p><p>　　Second ;development</p><p>　　Along with China's power electronics technology, the rapid development of mic

38、roelectronics technology, electrical automation concept has been out of the factory, and in transportation, agriculture, construction, office space and other aspects of a wide range of applications, electrical automation

39、 technology as the electrical engineering from the developed and closely with the electronics and information technology to combine an electrical engineering technology disciplines, after nearly a centur</p><p

40、>　　(A) all air-based power electronic switches. Thyristor in the fifties of last century there, it marks a new era of motion control. Although it is the first generation of electronic power devices, but was still in u

41、se. AC variable frequency technology appears then there have appeared a full-control devices, such as GTR and so on. This is the second generation of power electronic devices; followed this type of IGBT and MGT hybrid po

42、wer electronic devices can be called third-generation devices. Fin</p><p>　　(B) the direction of low frequency to high frequency circuits. Constantly updated to power electronic devices will inevitably lead

43、to the replacement converter circuit. </p><p>　　When applied to a thyristor, the DC transmission between the converter is mainly controlled rectifier, AC variable frequency drive is AC - DC - AC inverter. Wh

44、en the power switch to the second generation of electronic devices, when, PWM converters have adopted more appropriate. After using the PWM converter because not only improve the efficiency and to reduce the high harmoni

45、cs of the grid and reasonable solution to the motor torque ripple in the low frequency problem. With the application of i</p><p>　　(C) AC speed control theory. AC motor field oriented away from the city by t

46、he German scholar F · Blaschke made out, this theory put forward for the AC drive for high performance has laid a profound theoretical basis. However, he proposed this idea is far from control theory to achieve resu

47、lts. So 14 years later in Germany in 1985 after the University of Depenbrock Professor Rood also proposed the idea of ??direct torque control, followed by a push it into the field weakening speed range. It can</p>

48、<p>　　(D) Common drive in use. Universal Converter: serialization and batch, the largest market share of small and medium-power inverter. The first generation drive has gone through: common functional U / F control

49、 type; second generation: high-functional U / F type; the third generation: amount of controlled high dynamic performance. Inverters derived from voltage source (VSI) are ideally suited for supplying power to a resistive

50、 and inductive load and the applications that require constant torque op</p><p>　　Inverter control in practice concerns three aspects: fundamental frequency, amplitude, harmonic profile. </p><p>

51、;　　Fundamental frequency is either equal to the switching frequency of the inverter (square-wave and PWM inverters) or its simple fraction (1/3, 1/5, and so on) such as in Multiple PWM or sine PWM inverters.</p>&

52、lt;p>　　Power electronic applications require the amplitude control of output voltage or output current, called Voltage-Mode control and Current-Mode control respectively. An example of Voltage-Mode control is the adju

53、stable speed drives of induction and synchronous motors. An example of Current-Mode</p><p>　　control is a constant torque drive for induction motors. Output amplitude in both modes can be controlled by varyi

54、ng the DC source voltage or by varying the pulse-width (pulse-width modulation, PWM). The inverters based on the control of DC source voltage are also termed DC-Link Inverters. These inverters use an AC to controlled DC

55、converter on the input side. The inverter is square-wave controlled. This arrangement is expensive but exhibits a faster response time than PWM inverters. The control</p><p>　　The DC-AC inverter can be thoug

56、ht of as a three-position switch as shown in Fig.3-7(a). The load is connected to the pole of the switch and the first two positions are connected to dc voltage or dc current sources of opposite polarities. The third pos

57、ition is connected to the zero terminal of the source. The pole of the switch stays in the first and second positions for equal amounts of time in a switching period. The output waveform for zero amount of time on the th

58、ird position is a square wave</p><p>　　(E) the development of SCM. Dominant MCS-51 8-bit machines, although the dominant, but its function is still relatively simple, short set of instructions, hence suitabl

59、e for mass production of the PIC MCU promote the use of, it not only has high reliability and high security. </p><p>　　Third, the Electric Automation applications </p><p>　　(A) Buildings. Intell

60、igent building automation is bound to bring in electrical components, along with the rapid development of China's national economy and the development of digital electronic technology, no doubt, high-end intelligent

61、building has become the mainstream of today's construction industry. In order to achieve rational use of equipment, manpower saving in Sanming have a building automation control system equipment. For example: In the

62、design of buildings for power distribution, gro</p><p>　　Intelligent building, a large number of electronic devices and wiring systems, such as communications automation systems, fire alarm and fire control

63、systems, building automation systems, security monitoring systems, office automation systems, CCTV systems, as well as their corresponding wiring system. The electronic equipment and cabling system voltage levels are gen

64、erally lower for high anti-interference, fear by the lightning part. The establishment of strict and complete the mine structure. </p><p>　　(B) applies to clean air conditioning equipment. Air conditioning s

65、ystem controls automatic monitoring device can be designed into a single system of measurement, control systems, can also be designed into digital computer-controlled management system. </p><p>　　Temperature

66、 control. Gas purification system using DDC control wither. Installed in return air duct (return air temperature is similar to the clean room temperature) The temperature detected by temperature sensor sent a DX 9100, co

67、mpared with the set point with proportional plus integral plus derivative control operation, the output corresponding voltage signal, electric control valve controlling the heating or cold water electric control valve mo

68、vement and control the return air temperature mai</p><p>　　Solar water heating (SWH) SWH takes the radiation from the sun, present in all forms of daylight, to heat a combination of water and anti-freeze th

69、at passes through a solar collector mounted on the roof (as for PV).This is then pumped to a conventional hot water tank that has an additional heating coil, from which the sun is passed to the hot water that comes out o

70、f the taps .</p><p>　　Systems can provide a minimum of 60% of annual hot water needs and are always linked to the conventional heating system for back up .There are over 50000 systems of this type in the UK

71、and the cost depends on size and type of systems selected.</p><p>　　Small scale wind turbines Small wind turbines are sized at a hub height of 25 meters and under. Turbines need to be mounted on a tower

72、of a height that reduces the blocking effect of the buildings,residential properties and trees. They are noiseless,but a planning application will be required . Wind speeds are the vital factor,with wind speeds of 5m/s a

73、nd above ,at a height of 10m being recommended. </p><p>　　Biomass heating woodchipsform sustainably mannaged wood sources are a renewable resource and can bi burned in modrn,computer controlled boiler plant

74、to provide space and hot water heating in buildings.They word best when there is a consistent heat demand throughout the heating system and a storage area with easy access is required.Boiler plant costs are higherthan fo

75、r fossil,but woodchips are with easy access ia required.Boiler plant costs are higher than for fossil fuels,but woodchip are cheape</p><p>　　Futur of renewable energy</p><p>　　Reducing our depe

76、ndence on fossil fuels such an coal,oil and gas for the production of energy is vitally important,in order to reduce the impacts of global warming and climate change.Without doubt ,renewble energy technologies will play

77、a key role in achiening this,by providing a clean and sustainable source of energy,wohose generation will have no negative effects on the encironment.</p><p>　　Although electrical automation technology has b

78、een widely used in various sectors of our national production and areas, but it still requires constant innovation, continuous development.</p><p>　　關(guān)鍵詞:電氣自動化；涉及內(nèi)容；發(fā)展;應用</p><p><b>　　一涉及內(nèi)容&

79、lt;/b></p><p><b>　　電力系統(tǒng)</b></p><p>　　一個電路由一些元件，如電阻、電感和電容，以某種方式連接組成。如果電路中不包括電源，如電池或者發(fā)電機，則稱為無源網(wǎng)絡(luò)。另一方面，如果電路中有一個或多個電源，稱為有源網(wǎng)絡(luò)。在研究電路的行為中，確定存在于電路中的電壓和電流是我們感興趣的。由于一個電路網(wǎng)絡(luò)由無源元件組成，我們必須首先定義這些

80、元件的電的特性。</p><p>　　法拉第定律定義了理想電感兩端的電壓，指出：電感兩端的電壓與通過電感的電流的時間變化率成比例關(guān)系。因此我們得到以下公式：</p><p>　　電容兩端產(chǎn)生的電壓與積累在電容兩極的電荷成比例。由于電荷的積累可以表示為電荷增量的和或積分，我們得到等式。</p><p>　　有源的電設(shè)備涉及能量到電的轉(zhuǎn)變。例如，電池中的電能源于它內(nèi)部儲

81、存的化學能。發(fā)電機的電能由旋轉(zhuǎn)的電樞的機械能產(chǎn)生。</p><p>　　有源電路元件以兩種基本形式出現(xiàn)：電壓源和電流源。在理想模型中，電壓源產(chǎn)生一個恒值電壓，與其產(chǎn)生的電流無關(guān)的。前面提到的電池和發(fā)電機就屬于電壓源，因為它們的電壓本質(zhì)上對于負載恒定。另一方面，電流源產(chǎn)生一個電流，其大小與連接的負載無關(guān)。雖然電流源在實際應用中并不常見，但其概念廣泛用于描述放大裝置，如晶體管，通過一個等效電路。</p>

82、<p>　　分析電路的一個普通方法是網(wǎng)孔或回路分析。應用于這種方法的基本法則是基爾霍夫第一定律，它指出一個封閉回路電壓的代數(shù)和等于零，或者說，在任意封閉回路中，電壓升的代數(shù)和必須等于電壓降的代數(shù)和。網(wǎng)孔分析包含一個前提條件，即假設(shè)流過網(wǎng)絡(luò)中每一個回路的電流——術(shù)語為回路電流，代數(shù)求和每一個回路中的電壓降，并使每一個和為零。</p><p>　　在發(fā)展的變壓器，法國和交流輸電由L.巴黎戈拉爾和JD吉布斯

83、導致交流電力系統(tǒng)。</p><p>　　1889年，第一次在北美交流傳輸線將在俄勒岡州波特蘭之間威拉梅特大瀑布和實施。</p><p>　　這是一個單相線路傳輸功率為4,000公里，超過21 V系統(tǒng)的距離。隨著交流的發(fā)展多相系統(tǒng)由尼古拉特斯拉，成為更具吸引力的。通過1888年，特斯拉舉行交流多項專利電動機，發(fā)電機，變壓器和輸電系統(tǒng)。西屋公司購買了這些早期的發(fā)明專利，并形成了系統(tǒng)的基礎(chǔ)，現(xiàn)在

84、的交流。 </p><p>　　在19世紀90年代，有很大的爭議或交流電力行業(yè)是否應該統(tǒng)一于直流。到了世紀之交的，在交流系統(tǒng)贏得了原因出在下面的直流系統(tǒng)為： </p><p>　?。?）電壓水平可以很容易地改變了空調(diào)系統(tǒng)，從而提供了傳輸?shù)撵`活性，發(fā)電用不同的電壓和消費。 </p><p>　?。?）交流發(fā)電機簡單得多比直流發(fā)電機。 </p><p

85、>　?。?）交流電機和電機便宜簡單得多，比直流。 </p><p>　　因此，一個正常的電力系統(tǒng)連續(xù)運行的，提供可靠的電力供應給客戶的重要性是至關(guān)重要的。 </p><p>　　電力系統(tǒng)穩(wěn)定，可廣泛定義為干擾財產(chǎn)的權(quán)力系統(tǒng)，可繼續(xù)經(jīng)營的狀態(tài)下正常運行的平衡條件和后向遭受恢復一個可以接受的平衡狀態(tài)。 </p><p>　　在電力系統(tǒng)的不穩(wěn)定可能會表現(xiàn)在經(jīng)營方式和

86、多種不同的方式取決于系統(tǒng)配置。 </p><p>　　設(shè)計者的一個重要工作是減少輸出電壓或輸出電流的諧波成分，諧波成分是輸出電壓或輸出電流中不希望有的，因為諧波成分會降低功率因素。電機傳動系統(tǒng)中頻率諧波分量會引起機械共振。通過設(shè)置逆變器輸出濾波器可減小輸出電壓或輸出電流的諧波分量。</p><p>　　逆變器輸出低通濾波器的截止頻率設(shè)計成低于逆變器開關(guān)頻率（通常幾kHz）好幾倍。不過，在D

87、C-AC逆變器中，輸出電壓或輸出電流的基波成分大多是開關(guān)頻率的簡單分頻值，因此，就需要一種主動減少諧波分量的方法。要設(shè)計一個截止頻率介于基波和主要諧波頻率之間的高效低通濾波器是非常困難的。</p><p>　　變頻器控制涉及在特定的理想運行狀態(tài)下的逆變器調(diào)節(jié)，以使逆變器即使面對干擾、噪聲及建模誤差等情況時，也能在正常性能附近運行。我們可以分析電力電子變換器的靜態(tài)運行點附近的動態(tài)特性，因為變換器運行中包含了開關(guān)模式

88、，所以變換器總的數(shù)學模型是非線性的，靜態(tài)運行點附近的模型是線性的，可以采用我們所熟知的線性系統(tǒng)分析方法。</p><p><b>　　二、發(fā)展概況</b></p><p>　　伴隨著我國的電力電子技術(shù)、微電子技術(shù)的飛速發(fā)展,電氣自動化的概念已經(jīng)走出了工廠,并在交通、農(nóng)業(yè)、建筑、辦公場所等方面得到了廣泛的應用,電氣自動化技術(shù)作為從電氣工程技術(shù)發(fā)展出來的并與電子與信息技術(shù)

89、緊密結(jié)合起來的一門電氣工程應用技術(shù)學科,歷經(jīng)了近一個世紀的發(fā)展,電氣自動化技術(shù)已走過了從無到有、從發(fā)展到成熟的過程。而我國電氣自動化的研究工作可以追溯到上世紀的五十年代,可以說研究的時間不短,但是它依舊煥發(fā)著生氣與活力。下文就來簡述一下我國電氣自動化的發(fā)展歷程:</p><p>　　(1)全空型的電力電子開關(guān)。于上世紀五十年代晶閘管出現(xiàn)了,它標志著運動控制的新紀元。盡管它是第一代電子電力器件,但仍被沿用至今。隨后

90、交流變頻技術(shù)出現(xiàn)后相繼有出現(xiàn)了全控制式器件如GTR等。這是電力電子器件的第二代;接下來是IGBT和MGT這一類復合型電力電子器件可以稱為第三代器件。最后是功率集成電路,PIC即第四代電力電子器件。</p><p>　　(2)由低頻向高頻方向發(fā)展的電路。不斷更新的電力電子器件勢必要引發(fā)變換器電路的換代。</p><p>　　當應用于普通晶閘管時,直流傳動的變換器主要是整流相互控制,交流變頻傳

91、動則是交—直—交變頻器。當電力電子器件轉(zhuǎn)換到第二代的時候,PWM變換器采用的相應也要多些。因為采用了PWM變換器之后不僅提高了功效,并且能夠減少高次諧波對電網(wǎng)的影響,合理解決了電動機在低頻區(qū)的轉(zhuǎn)矩脈動問題。隨著應用的深入,PWM也存在著諸多缺陷,因此也就有了諧振式直流逆變器電路的發(fā)展。</p><p>　　(3)交流調(diào)速控制理論。交流電機磁場定向遠離市由德國學者F·Blaschke所提出來的,這一理論的

92、提出為交流傳動高性能控制奠定了深刻的理論基礎(chǔ)。但他提出的這個思想遠不能夠達到理論的操控效果。于是事隔14年后于1985年德國魯?shù)麓髮W的Depenbrock教授又提出了直接轉(zhuǎn)矩控制的思想,緊接著有將它推放到了弱磁調(diào)速的范圍內(nèi)?？梢哉f他的這一控制思想新穎,控制結(jié)構(gòu)簡單明了,信號處理的物理概念明確,是一種高靜動態(tài)性能的新型交流調(diào)速方法。</p><p>　　(4)通用變頻器的投入使用。通用變頻器:系列化、批量化、占市場

93、量最大的中小功率變頻器。先后變頻器經(jīng)歷了第一代:普通功能型U/F控制型;第二代:高功能型U/F型;第三代:高動態(tài)性能適量控制型。</p><p>　　來自電壓源逆變器（逆變器）是理想的供電，以一個電阻和電感負載和應用，需要交流電動機適用于恒轉(zhuǎn)矩運行。電流源逆變器（CSI）的非常適合對主要供電電容負載和交流電壓巴士。變頻器可以進一步對輸出變量的控制方式：電壓或電流來分類。 </p><p>

94、　　變頻控制在實踐中關(guān)注三個方面：基本頻率，振幅，諧波形象。 </p><p>　　基本頻率是不是等于逆變器（方波和PWM逆變器）或簡單的分數(shù)（1 / 3，1 / 5的開關(guān)頻率，等等），如在PWM或多個正弦脈寬調(diào)制逆變器。 </p><p>　　電力電子應用要求的輸出電壓或輸出幅度控制電流，稱為電壓模式控制和電流模式控制的分別。一種電壓模式控制的例子是感應和同步電機調(diào)速驅(qū)動器。一種電流模式

95、的例子 </p><p>　　控制是異步電動機恒轉(zhuǎn)矩驅(qū)動器。在兩種模式輸出幅度可以控制通過改變直流電源電壓或通過改變脈沖寬度（脈沖寬度調(diào)制，脈寬調(diào)制）。對直流電壓源逆變器控制方法，也稱為直流環(huán)節(jié)逆變器。這些逆變器使用交流電，以控制直流轉(zhuǎn)換器的輸入端。該逆變器是方波控制。這項安排是昂貴的，但表現(xiàn)出比PWM逆變器更快的響應時間。該控制電路也比較簡單。諧波貌相是一個額外的功能添加在幅度控制。諧波譜的目的是加強了輸出電壓

96、和消除或減少高次諧波幅值的基本組成部分。這些技術(shù)包括把開槽或增加脈沖來一步一個基地的脈搏。其他技術(shù)包括了每個周期基本多個脈沖，每個脈沖寬度調(diào)制，以達到理想的波的輸出波形（正弦脈寬調(diào)制）的形成。 </p><p>　　在DC - AC逆變器可以被認為是一個三位置開關(guān)在圖3 - 7（a）所示。負載連接到交換機的第一個桿位和兩個位置連接到直流電壓或直流電流源的極性相反。第三位是連接到源零終端。開關(guān)的桿停留在等量的時間在

97、一個開關(guān)周期的第一和第二的位置。關(guān)于第三位為0的時間輸出波形是方波。為非零時間輸出脈沖波的波形。這三個位置開關(guān)，可合成2單向在圖3 - 7所示的電子開關(guān)（b）項。這三個位置開關(guān)，可合成2單向在圖3 - 7所示的電子開關(guān)（b）項。開關(guān)的第三位是把兩個模擬開關(guān)逆變器拓撲和小康在滬深拓撲。</p><p>　　(5)單片機的發(fā)展。占主導地位的MCS-51的8位機雖占主導地位,但是它的功能還比較簡單,指令集短小,因此就有

98、了適合大批量生產(chǎn)的PIC系列單片機的推廣使用,它不僅具有很高的可靠性,而且保密性高。</p><p>　　三、電氣自動化的應用</p><p>　?。?）建筑中的應用。智能化建筑勢必要引入電氣自動化的成分,隨著我國國民經(jīng)濟的飛速發(fā)展以及數(shù)字電子化科技發(fā)展,無疑,高檔智能化建筑已經(jīng)成為了當今建筑界的主流方向。為了達到設(shè)備的合理利用,三明的人力的節(jié)省就有了建筑設(shè)備的自動化控制系統(tǒng)。例如:在建筑

99、物供配電設(shè)計中,接地系統(tǒng)沒計占有重要的地位,因為它關(guān)系到供電系統(tǒng)的可靠性,安全性。IN—S是一個三相四線J/NPE線的接地系統(tǒng)。通常建筑物內(nèi)設(shè)有獨立變配電所時進線采用該系統(tǒng)。TN—s系統(tǒng)的特點是,中性線N與保護接地線PE除在變壓器中性點共同接地外,兩線不再有任何的電氣連接。中性線N是帶電的,而PE線不帶電。該接地系統(tǒng)完全具備安全和可靠的基準電位。只要像TN—C—S接地系統(tǒng),采取同樣的技術(shù)措施,TN—S系統(tǒng)可以用作智能建筑物的接地系統(tǒng)。智

100、能建筑應沒置電子設(shè)備的直流接地,交流工作接地,安全保護接地及普通建筑也應具備的防雷保護接地。</p><p>　　智能化建筑內(nèi)有大量的電子設(shè)備與布線系統(tǒng),如通信自動化系統(tǒng),火災報警及消防聯(lián)動控制系統(tǒng),樓宇自動化系統(tǒng),保安監(jiān)控系統(tǒng),辦公自動化系統(tǒng),閉路電視系統(tǒng)等,以及他們相應的布線系統(tǒng)。這些電子設(shè)備及布線系統(tǒng)一般均屬于耐壓等級低,防干擾要求高,最怕受到雷擊的部分。建立嚴密,完整的防雷結(jié)構(gòu)。智能建筑多屬于一級負荷,應