【正文】 可以考慮基頻以下和基頻以上兩種情況。當(dāng)電動(dòng)勢(shì)值較高時(shí)，可以忽略定子繞組的漏磁阻抗壓降，認(rèn)為定子相電壓約等于，則/=常值，即恒壓頻比的控制方式。圖61 異步電動(dòng)機(jī)變頻調(diào)速的控制特性把基頻以下和基頻以上兩種情況的控制特性畫(huà)在圖61上。在基頻以下，磁通恒定時(shí)轉(zhuǎn)矩也恒定，屬于“恒轉(zhuǎn)矩調(diào)速”，在基頻以上，轉(zhuǎn)速升高時(shí)轉(zhuǎn)矩降低，屬于“恒功率調(diào)速”。但是由于同步電動(dòng)機(jī)的轉(zhuǎn)子結(jié)構(gòu)與異步電動(dòng)機(jī)不同，其矢量坐標(biāo)變換有自己的特點(diǎn)，這些主要特點(diǎn)是：定子有三相交流繞組，轉(zhuǎn)子為直流勵(lì)磁或永磁。忽略阻尼繞組的效應(yīng)。暫先忽略定子電阻和漏抗的影響。圖62 二極同步電動(dòng)機(jī)的物理模型圖中，定子三相繞組軸線A、B、C是靜止的，三相電壓、和三相電流、都是平衡的，轉(zhuǎn)子以同步轉(zhuǎn)速旋轉(zhuǎn)，轉(zhuǎn)子上的勵(lì)磁繞組在勵(lì)磁電壓供電下流過(guò)勵(lì)磁電流。在同步電動(dòng)機(jī)中，除轉(zhuǎn)子直流勵(lì)磁外，定子磁動(dòng)勢(shì)還產(chǎn)生電樞反應(yīng)，直流勵(lì)磁與電樞反應(yīng)合成起來(lái)產(chǎn)生氣隙磁通，合成磁通在定子中敢于的電動(dòng)勢(shì)與外加電壓基本平衡。圖63 磁動(dòng)勢(shì)和磁通的空間矢量圖圖64 電壓、電流和磁鏈的時(shí)間向量圖圖64畫(huà)出了定子一相繞組的電壓、電流與磁鏈的時(shí)間相量圖。加入了矢量運(yùn)算器，用來(lái)控制同步電動(dòng)機(jī)的定子電流和勵(lì)磁電流，即可實(shí)現(xiàn)同步電動(dòng)機(jī)的矢量控制，其原理如圖65所示。圖65 同步電動(dòng)機(jī)基于電流模型的矢量控制系統(tǒng)根據(jù)機(jī)電能量轉(zhuǎn)換原理，同步電動(dòng)機(jī)的電磁轉(zhuǎn)矩可以表達(dá)為：旋轉(zhuǎn)磁動(dòng)勢(shì)幅值：整理以后得其中，上式表明，經(jīng)矢量分解后，同步電動(dòng)機(jī)的轉(zhuǎn)矩公式獲得了和直流電動(dòng)機(jī)轉(zhuǎn)矩一樣的表達(dá)式。如圖65所示，同步電動(dòng)機(jī)矢量控制系統(tǒng)采用了和直流電動(dòng)機(jī)調(diào)速系統(tǒng)相似的雙閉環(huán)控制結(jié)構(gòu)。與此同時(shí)，乘以系數(shù)即得合成勵(lì)磁電流的給定信號(hào)，另外，按功率因數(shù)要求還可得定子電流勵(lì)磁分量給定信號(hào)。通過(guò)ACR和AFR實(shí)行電流閉環(huán)控制，可使實(shí)際電流、以及跟隨其給定值變化，獲得良好的動(dòng)態(tài)性能。第七章 Auto CAD 2004繪圖 CAD簡(jiǎn)介Auto CAD是由美國(guó)Autodesk公司開(kāi)發(fā)的大型計(jì)算機(jī)輔助繪圖軟件，主要用來(lái)繪制工種圖樣。當(dāng)前Auto CAD已經(jīng)廣泛應(yīng)用于機(jī)械、電子、服裝、建筑等設(shè)計(jì)領(lǐng)域。作為一個(gè)通用的工種設(shè)計(jì)平臺(tái)，Auto CAD還擁有強(qiáng)大的人機(jī)交互能力和簡(jiǎn)便的操作方法，十分方便廣大普通用戶，下面介紹一下Auto CAD的主要功能。精確定位定形功能：Auto CAD提供了坐標(biāo)輸入、對(duì)象捕捉、柵格捕捉、追蹤等功能，利用這些功能可以精確地為圖形對(duì)象定位和定形。圖形輸出功能：圖形輸出包括屏幕顯示和打印出圖，Auto CAD提供了方便的縮放和平移等屏幕顯示工具，模型空間、圖紙空間、布局、發(fā)布和打印等功能極大地豐富了出圖選擇。 輔助設(shè)計(jì)功能：可以查詢繪制好的圖形的長(zhǎng)度、面積、體積和力學(xué)性能等；提供多種軟件的接口，可方便地將設(shè)計(jì)數(shù)據(jù)和圖形在多個(gè)軟件中共享，進(jìn)一步發(fā)揮各軟件的特點(diǎn)和優(yōu)勢(shì)。通過(guò)DXF、IGES等圖形數(shù)據(jù)接口，可以實(shí)現(xiàn)Auto CAD和其他系統(tǒng)的集成。在實(shí)際工作生產(chǎn)中，設(shè)計(jì)師會(huì)利用已有的定子沖片圖設(shè)計(jì)電機(jī)繞組，主要是因?yàn)檫@樣可以有效的節(jié)省設(shè)計(jì)步驟，充分的利用已有資源。圖71 定子沖片圖跟定子沖片圖一樣，在實(shí)際工作生產(chǎn)中，設(shè)計(jì)師會(huì)利用已有的轉(zhuǎn)子沖片圖設(shè)計(jì)電機(jī)繞組，主要是因?yàn)檫@樣可以有效的節(jié)省設(shè)計(jì)步驟，充分的利用已有資源。圖72 轉(zhuǎn)子沖片圖在設(shè)計(jì)電機(jī)繞組完成以后，根據(jù)設(shè)計(jì)結(jié)果需要畫(huà)出繞組圖。因此必須全面地、綜合地看問(wèn)題，并能因時(shí)因地制宜，針對(duì)具體情況采取不同的解決方案。 通過(guò)這次畢業(yè)設(shè)計(jì)，尤其在手工核算過(guò)程中，我重新溫習(xí)了關(guān)于《電機(jī)學(xué)》、《電機(jī)設(shè)計(jì)》等方面的知識(shí)，加強(qiáng)了自己較為薄弱的基礎(chǔ)知識(shí)。手工核算主要的目的主要是使我們熟悉電機(jī)設(shè)計(jì)的一般步驟、程序，對(duì)電機(jī)各參量的相互聯(lián)系有更實(shí)際的認(rèn)識(shí)，為下一步的優(yōu)化設(shè)計(jì)打下基礎(chǔ)。經(jīng)過(guò)這一個(gè)學(xué)期的做畢業(yè)設(shè)計(jì)的過(guò)程。作為一名工科的學(xué)生，我更深深地體會(huì)到知識(shí)更新、學(xué)無(wú)止境的重要性，因此，在今后的工作和生活當(dāng)中，將不斷地積極求學(xué)進(jìn)取，生命不息，讀書(shū)不止，這樣才能豐富和完善自己。致謝本次畢業(yè)設(shè)計(jì)歷時(shí)三個(gè)多月，從選題、開(kāi)題報(bào)告、復(fù)算過(guò)程到CAD繪制沖片圖、繞組圖，完成論文。本次畢業(yè)設(shè)計(jì)的完成過(guò)程中，還得到了黃教授門下研究生王愛(ài)鳳學(xué)姐的幫助，在此一并表示感謝。(2) ia0, ib0 and ic0。(4) ia0, ib0 and ic0。(6) ia0, ib0 and ic0.It is very important and difficult to detect the zerocross point or the polarity of each phase , if the zerocross point is detect directly through A/D converter of DSP or MCU, bigger measurement deviation will be led especially under the condition of small current, which will result in bigger deadtime pensation deviation and also affect the result of deadtime pensation. Therefore, this paper adopts an indirectly method to detect the zerocross point of phase current, which is based on the current vector angle φ in the twophase static reference frame.For convenient analysis and illustration, place the threephase currents ia, ib, ic in the threephase static reference frame and the two current ponents iα , iβ of the current vector in the twophase static reference frame into the same figure, which is shown in . According to the polarity of threephase currents ia, ib, ic, the iα iβ plane in the twophase static reference frame can be divided into six sectors: I(1), II(2), III(3), IV(4), V(5) and VI(6). For each sector in the iαiβ plane, there is a corresponding deadtime pensation rule. In other words, once the sector which the current vector belongs to is known, the deadtime effect can be pensated according to the corresponding pensation , recognizing the sector number of the current vector is the key problem. In this paper, the sector number is determined by thecurrent vector angle φ which can be calculated through the α and β axis ponents of the stator current vector. Equation (1) shows the calculation method of the current vector φ, and equation (2) shows the relationship between the sector number and the current vector φ. φ=kπ+arctan（iβ/iα） (k = 0,1). Current Polarity and Current Vector Angle ?TABLE IDEADTIME COMPENSATION RULES TABLE OF SVPWM(2)For threephase voltage source inverter, the essence of deadtime pensation is to pensating the voltage deviation. However, in the digital motor driving and control system, voltage regulation is implemented through pulse width modulation, that is, through regulating the duty cycle of voltage pulse which has something to do with the pulse width T in one PWM period Tpwm. Therefore, in fact it is the pulse width T that is pensated in the practical application. TABLE I shows the deadtime pensation rules corresponding with the polarity of threephase currents ia,ib,ic and the sector number of the current vector in the iαiβ plane. It can be seen that for different sectors of the iαiβ plane, the pensation values are correspondingly different. In one word, the proposed deadtime pensation method can be carried out through the following steps:(1) Calculate the current vector angle φ through the α and β axis ponents of the stator current vector in the twophase static reference frame according to equation (1).(2) Determine the sector number through the current vector angle φ according to equation (2).(3) Execute the deadtime pensation algorithm according to the pensation rules table TABLE I.III. EXPERIMENTSIn order to test and verify the proposed deadtime pensation method of SVPWM, experiments are established and made. The experiment system consists of PMSM, threephase voltage source inverter, control platform, dynamometer, heat dissipation system, et type of IGBT in the inverter is CM600DY24A produced by Mitsubishi. The control platform is based on DSP TMS320F2812 produced by Texas is a special motor control DSP which has many advantages and can implement highperformance motor control such as FOC (Field Oriented Control) and DTC (Direct Torque Control). The main parameters of the control objectPMSM used in experiments are listed in TABLE II.For different pulse width pensation values of , and , the deadtime pensation experiments are all made. shows the experiment waveforms of threephase stator currents and the sector number of stator current vector for different pulse width pensation values, and shows the corresponding frequency spectrums.TABLE IIMAIN PARAMETERS OF PMSM USED