外文翻譯--基本的ac驅(qū)動

1、<p>　　基本的AC驅(qū)動 </p><p>　　AC驅(qū)動是一種逆變器，是可調(diào)節(jié)的頻率驅(qū)動，可以被用于提供按設(shè)備的期望來控制交流電機的速度。西門子(AC驅(qū)動)是使用用語SIMOVERT來辨認的西門子電機逆變器。AC驅(qū)動接受交

2、流電源并且把它轉(zhuǎn)換成一可調(diào)整的頻率，可調(diào)整的電壓來控制電機的輸出。一臺典型的逆變器接受380 V三相交流電壓，對電機來說分別是50Hz輸入電源和反過來提供適當(dāng)?shù)碾妷汉皖l率來達到特定的速度。三共同性反轉(zhuǎn)類型是可控的電壓型逆變器，當(dāng)前有源逆變器(CSI)和脈沖寬度調(diào)制(PWM)。另外一種AC驅(qū)動是循環(huán)逆變器。這些通常被用在大型電機中，在這個過程中是不可控的。所有AC驅(qū)動都是把交流轉(zhuǎn)換成直流，然后通過各種各樣開關(guān)技術(shù)把直流逆變?yōu)橐环N可調(diào)的電壓

3、、頻率的電源。</p><p><b>　　可控電壓型逆變器</b></p><p>　　可控電壓型變換器是使用SCR管的整流橋把交流電壓轉(zhuǎn)換成成直流。 SCR管提供控制被矯正的直流電壓的值大約從0V到600 V。L1開關(guān)和C1電容器組成直流環(huán)節(jié)部分使其轉(zhuǎn)換成平滑的直流電。逆變器部分包括六個開關(guān)設(shè)備。例如可控硅整流器、雙極性晶體管、MOSFETS和IGBT管等各種各樣

4、的設(shè)備都可以使用。根據(jù)圖所顯示運用雙極晶體管的一臺逆變器?？刂七壿?沒顯示)使用一個微處理器控制開關(guān)開斷來提供可變的電壓和頻率給電機。</p><p>　　此種開關(guān)通常有六個步驟，因為它采取六個60°步驟來完成一個360°周期。雖然電機應(yīng)該使用光滑的正弦波，但是六步的輸出可以令人更滿意地使用了。 這種開關(guān)的缺點主要是每一個開關(guān)裝置容易發(fā)生轉(zhuǎn)矩脈動，例如一雙極性晶體管開關(guān)裝置。在的低速電機中脈動

5、是明顯的。非正弦信號的電流波形導(dǎo)致額外發(fā)熱。</p><p><b>　　電流源型逆變器 </b></p><p>　　電流源型逆變器(CSI)使用SCR輸出產(chǎn)生一個易變的直流電壓環(huán)節(jié)。對電機來說逆變器部分也使用SCR作為開關(guān)裝置。電流源型逆變器控制電機的電流。馬達必須配以合適的驅(qū)動。從輸出中可以看出是由變換造成。在低速電流脈沖由電機中的齒輪引起。</p>

6、<p><b>　　脈寬調(diào)制</b></p><p>　　脈寬調(diào)制(PWM)驅(qū)動，如西門子MICROMASTER和MASTERDRIVE VC，提供更多正弦電流輸出控制頻率和電壓的供應(yīng)給交流電機。PWM驅(qū)動是高效率和典型的提供高水平的控制。一個基本的PWM驅(qū)動包括整流器、直流環(huán)節(jié)、邏輯控制和逆變器.</p><p><b>　　整流器和直流環(huán)節(jié)

7、 </b></p><p>　　整流器部分含有一個固定的二極管橋式整流器把三相電源轉(zhuǎn)換成直流電壓。L1電阻和C1電容器使被轉(zhuǎn)換的直流電壓比較光滑。被矯正的直流電壓值大約是1.35倍電源電壓的線間短路混線兩線間電壓值。被矯正的直流電壓值大約是514 V由380 V供應(yīng)。</p><p><b>　　邏輯控制和逆變器 </b></p><p

8、>　　電機所需的輸出電壓和頻率是由邏輯控制和逆變器部分控制的。逆變器部分包括六個開關(guān)裝置。如可控硅整流器、雙極晶體管、MOSFETS和IGBTs這樣的各種各樣的設(shè)備都可以使用。根據(jù)概要顯示要運用IGBTs的一臺變換器?？刂七壿嬍褂靡粋€微處理器接通IGBTs并且提供一個易變的電壓和頻率給電機。</p><p><b>　　IGBTs </b></p><p>　

9、　IGBTs (絕緣柵雙極型功率管)提供一個高速度開關(guān)必須為PWM變換器操作。IGBTs 能夠每秒能關(guān)斷數(shù)千次。其次，IGBT可能是在不少于大約400到500納秒打開。IGBT包括一個柵極、一個源極和一個發(fā)射極。當(dāng)一個正電壓(典型的+15 V)被用于將起動的IGBT的柵極，這是一個類似閉合的開關(guān)。電流將流動在這個源極和發(fā)射極之間。IGBT是通過取消通過這個柵極的正電壓來關(guān)閉的。在狀態(tài)期間IGBT 柵極電壓通常設(shè)在一個負電壓(-15V)來

10、防止其打開。 </p><p><b>　　PWM輸出 </b></p><p>　　這有幾個PWM模塊化技術(shù)。它是在這本書的全部范圍之外詳細描述的。是根據(jù)文本和例證描述一典型脈沖寬度模塊化的方法。IGBT (或其他類型開關(guān)設(shè)備) 能在連接被交換直流電壓的正值到馬達 (從逆變器的514 V)。電流流動到馬達中。在一個短的時期內(nèi)IGBT被接通，僅準(zhǔn)許少量的加強的電流在馬

11、達形成然后關(guān)閉。IGBT被接通和斷開之間有各很長且緩慢的時期，允許電流建立由更高的水平?jīng)Q定的，直到當(dāng)前在馬達到達峰頂。然后IGBT被接通的短周期內(nèi)，在馬達中減少電流的建立。負正弦波的一半是通過交換IGBT的連接引起的直流電壓的負值被轉(zhuǎn)換引起的。</p><p><b>　　PWM電壓和電流 </b></p><p>　　由PWM生產(chǎn)的正弦的電流減少扭矩脈動、低速電機的

12、鑲齒效應(yīng)，當(dāng)用到六步輸出時，電機的損失明顯極少。</p><p>　　電壓和頻率通過在AC驅(qū)動內(nèi)的電路來控制。固定的直流電壓(514 V)是調(diào)制或截去以這種方法來提供可變的電壓和頻率。需要在低頻率輸出一個低電壓時，開關(guān)裝置的單位時間內(nèi)開關(guān)時間更短，電壓和電流在電機中是很低的。需要在高頻率輸出一個高電壓時，開關(guān)裝置的單位時間內(nèi)開關(guān)時間較長。允許較高的電壓和電流在電機中。</p><p>　　

13、The Basic AC Drives</p><p>　　AC drives, inverters, and adjustable frequency drives are all terms that are used to refer to equipment designed to control the speed of an AC motor. The term SIMOVERT is used by

14、 Siemens to identify a Siemens Motor inverter (AC drive).AC drives receive AC power and convert it to an adjustable frequency, adjustable voltage output for controlling motor operation. A typical inverter receives 380 VA

15、C, three-phase,50 Hz input power and in turn provides the proper voltage and frequency for a given spe</p><p>　　Variable Voltage Inverter </p><p>　　The variable voltage inverter uses an SCR conv

16、erter bridge to convert the incoming AC voltage into DC. The SCRs provide a means of controlling the value of the rectified DC voltage from 0 to approximately 600 VDC. The L1 choke and C1 capacitor(s) make up the DC link

17、 section and smooth the converted DC voltage. The inverter section consists of six switching devices. Various devices can be used such as thyristors, bipolar transistors, MOSFETS, and IGBTs. The following schematic shows

18、 an inverter t</p><p>　　This type of switching is often referred to as six-step because it takes six 60°steps to complete one 360°cycle. Although the motor prefers a smooth sine wave, a six-step ou

19、tput can be satisfactorily used. The main disadvantage is torque pulsation which occurs each time a switching device, such as a bipolar transistor, is switched. The Pulsations can be noticeable at low speeds as speed var

20、iations are sometimes referred to as cogging. The non-sinusoidal current waveform causes extra heating in t</p><p>　　Current Source Inverter </p><p>　　The current source inverter (CSI) uses an S

21、CR input to produce a variable voltage DC link. The inverter section also uses SCRs for switching the output to the motor. The current source inverter controls the current in the motor. The motor must be care fully match

22、ed to the drive. Current spikes, caused by switching, can be seen in the output. At low speeds current pulses can causes the motor to cog.</p><p>　　Pulse Width Modulation </p><p>　　Pulse width m

23、odulation (PWM) drives, like the Siemens MICROMASTER and MASTERDRIVE VC, provide a more sinusoidal current output to control frequency and voltage supplied to an AC motor. PWM drives are more efficient and typically prov

24、ide higher levels of performance. A basic PWM drive consists of a converter, DC link, control logic, and an inverter.</p><p>　　Converter and DC Link </p><p>　　The converter section consists of a

25、 fixed diode bridge rectifier which converts the three-phase power supply to a DC voltage. The L1 choke and C1 capacitor(s) smooth the converted DC voltage. The rectified DC value is approximately 1.35 times the line-to-

26、line value of the supply voltage. The rectified DC value is approximately 650 VDC for a 480 VAC supply.</p><p>　　Control Logic and Inverter </p><p>　　Output voltage and frequency to the motor ar

27、e controlled by the control logic and </p><p>　　inverter section. The inverter section consists of six switching devices. Various devices can be used such as thyristors, bipolar transistors, MOSFETS and IGBT

28、s. following schematic shows an inverter that utilizes IGBTs. The control logic uses a microprocessor to switch the IGBTs on and off providing a variable voltage and frequency to the motor.</p><p><b>　

29、　IGBTs </b></p><p>　　IGBTs (insulated gate bipolar transistor) provide a high switching speed necessary for PWM inverter operation. IGBTs are capable of switching on and off several thousand times a se

30、cond. An IGBT can turn on in less than 400 nanoseconds and off in approximately 500 nanoseconds. An IGBT consists of a gate, collector and an emitter. When a positive voltage (typically +15 VDC) is applied to the gate th

31、e IGBT will turn on.This is similar to closing a switch. Current will flow between the collector and</p><p>　　PWM Output </p><p>　　There are several PWM modulation techniques. It is beyond the s

32、cope of this book to describe them all in detail. The following text and illustrations describe a typical pulse width modulation method. An IGBT (or other type switching device) can be switched on connecting the motor to

33、 the positive value of DC voltage (650 VDC from the converter). Current flows in the motor. The IGBT is switched on for a short period of time, allowing only a small amount of current to build up in the motor and then<

34、;/p><p>　　PWM Voltage and Current </p><p>　　The more sinusoidal current output produced by the PWM reduces the torque pulsations, low speed motor cogging, and motor losses noticeable when using a s

35、ix-step output.</p><p>　　The voltage and frequency is controlled electronically by circuitry within the AC drive. The fixed DC voltage (650 VDC) is modulated or clipped with this method to provide a variable

36、 voltage and frequency. At low output frequencies a low output voltage is required. The switching devices are turned on for shorter periods of time. Voltage and current build up in the motor is low. At high output freque