風(fēng)籠式選粉機(jī)總體及其傳動(dòng)設(shè)計(jì)【水泥圈流系統(tǒng)】【說(shuō)明書(shū)+CAD+UG】
風(fēng)籠式選粉機(jī)總體及其傳動(dòng)設(shè)計(jì)【水泥圈流系統(tǒng)】【說(shuō)明書(shū)+CAD+UG】,水泥圈流系統(tǒng),說(shuō)明書(shū)+CAD+UG,風(fēng)籠式選粉機(jī)總體及其傳動(dòng)設(shè)計(jì)【水泥圈流系統(tǒng)】【說(shuō)明書(shū)+CAD+UG】,風(fēng)籠式選粉機(jī),總體,整體,及其,傳動(dòng),設(shè)計(jì),水泥,系統(tǒng),說(shuō)明書(shū),仿單,cad,ug
編號(hào)
無(wú)錫太湖學(xué)院
畢業(yè)設(shè)計(jì)（論文）
題目： 風(fēng)籠式選粉機(jī)總體及其傳動(dòng)設(shè)計(jì)
信機(jī) 系 機(jī)械工程及自動(dòng)化 專業(yè)
學(xué) 號(hào)： 0923080
學(xué)生姓名： 王 標(biāo)
指導(dǎo)教師： 林承德 （職稱：教授 ）
（職稱： ）
2013年5月25日
1
編 號(hào)
無(wú)錫太湖學(xué)院
畢業(yè)設(shè)計(jì)（論文）
相關(guān)資料
題目： 風(fēng)籠式選粉機(jī)總體及其傳動(dòng)設(shè)計(jì)
信機(jī) 系 機(jī)械工程及自動(dòng)化專業(yè)
學(xué) 號(hào)： 0923080
學(xué)生姓名： 王 標(biāo)
指導(dǎo)教師： 林承德 （職稱：教授 ）
（職稱： ）
2013年5月25日
無(wú)錫太湖學(xué)院本科畢業(yè)設(shè)計(jì)（論文）
誠(chéng) 信 承 諾 書(shū)
本人鄭重聲明：所呈交的畢業(yè)設(shè)計(jì)（論文） 風(fēng)籠式選粉機(jī)的總體及其傳動(dòng)設(shè)計(jì) 是本人在導(dǎo)師的指導(dǎo)下獨(dú)立進(jìn)行研究所取得的成果，其內(nèi)容除了在畢業(yè)設(shè)計(jì)（論文）中特別加以標(biāo)注引用，表示致謝的內(nèi)容外，本畢業(yè)設(shè)計(jì)（論文）不包含任何其他個(gè)人、集體已發(fā)表或撰寫的成果作品。
班 級(jí)： 機(jī)械92
學(xué) 號(hào)： 0923080
作者姓名：
2013 年 5 月 25 日
目 錄
一、畢業(yè)設(shè)計(jì)（論文）開(kāi)題報(bào)告
二、畢業(yè)設(shè)計(jì)（論文）外文資料翻譯及原文
三、學(xué)生“畢業(yè)論文（論文）計(jì)劃、進(jìn)度、檢查及落實(shí)表”
四、實(shí)習(xí)鑒定表
無(wú)錫太湖學(xué)院
畢業(yè)設(shè)計(jì)（論文）
開(kāi)題報(bào)告
題目：風(fēng)籠式選粉機(jī)總體及傳動(dòng)設(shè)計(jì)
機(jī)電系 機(jī)械工程及其自動(dòng)化專業(yè)
學(xué) 號(hào)： 0923080
學(xué)生姓名： 王標(biāo)
指導(dǎo)教師： 林承德 （職稱：教授 ）
（職稱： ）
2013 年 5 月 25日
課題來(lái)源
課題來(lái)源于生產(chǎn)實(shí)際。
課題研究的主要內(nèi)容是配套圈流系統(tǒng)水泥磨φ3.5×12m,Q＝70-90t/h的風(fēng)籠式效選粉機(jī)，重點(diǎn)設(shè)計(jì)傳動(dòng)與殼體部件。
選粉機(jī)是水泥工業(yè)閉路循環(huán)粉磨系統(tǒng)中的一個(gè)重要組成設(shè)備，是隨干法閉路粉磨技術(shù)的進(jìn)步而發(fā)展的。先后產(chǎn)生了第一代—普通撒料式空氣選粉機(jī)，第二代—旋風(fēng)式選粉機(jī)，第三代—以O(shè)－Sepa選粉機(jī)為代表的籠式選粉機(jī)稱為高效選粉機(jī)。在此基礎(chǔ)上不少公司推出了類似的籠式選粉機(jī)。國(guó)外品牌有：Sturtvent公司的SD選粉機(jī)、Krupp polysius公司的sepol選粉機(jī)、KHD公司的SKS-Z選粉機(jī)、FLS公司的Sepax選粉機(jī)、Chr. pfeifer公司的QDK選粉機(jī)、O&D公司的橫流選粉機(jī)等。國(guó)內(nèi)產(chǎn)品有由天津院、南水院等引進(jìn)的O－Sepa選粉機(jī)、合肥院的DS、HES選粉機(jī)、北京院的高效選粉機(jī)等。
雖然籠式高效選粉機(jī)以其卓越的性能得到人們的肯定，但它結(jié)構(gòu)復(fù)雜，加工制造費(fèi)用較高，還要增加收集成品的高濃度袋式收塵器，并且操作要求及管理要求也相應(yīng)較高。我國(guó)建材行業(yè)針對(duì)我國(guó)的國(guó)情，在選粉機(jī)的發(fā)展上進(jìn)行了多次的改進(jìn)，也發(fā)展了各種各樣的高效選粉機(jī)，如高效渦流、NHX型高效轉(zhuǎn)子式、HFS型和DS型組合式高效選粉機(jī)等，都取得了一些效果。還有的將第一、二代選粉機(jī)稍加改造，分別稱為離心式高效選粉機(jī)和旋風(fēng)式高效選粉機(jī)等。轉(zhuǎn)子式選粉機(jī)也是其中一個(gè)杰出的代表。
轉(zhuǎn)子式選粉機(jī)是在旋風(fēng)式選粉機(jī)的基礎(chǔ)上發(fā)展而來(lái)，投資較省，選粉效率較高。但隨著我國(guó)節(jié)能降耗的不斷深入，對(duì)于粉磨系統(tǒng)來(lái)說(shuō)，粉磨效率要求更高，電耗更低，成本更低，這就要求組成粉磨系統(tǒng)的重要部分－－選粉機(jī)。優(yōu)秀的選粉機(jī)要求具有良好的分散功能、最先進(jìn)的分級(jí)機(jī)理、廉價(jià)而實(shí)用的收集裝置。把我國(guó)目前使用較廣泛的轉(zhuǎn)子式選粉機(jī)和逐漸被大家認(rèn)可的O－Sepa選粉機(jī)，以先進(jìn)的懸浮分散技術(shù)、預(yù)分級(jí)技術(shù)、平面渦流分級(jí)技術(shù)以及內(nèi)循環(huán)收集技術(shù)統(tǒng)一在一起，研制開(kāi)發(fā)了一些應(yīng)用于先進(jìn)工藝流程中的新型組合式選粉機(jī)。與此同時(shí)出現(xiàn)其它高效節(jié)能技術(shù)，例如：KX型高效二次風(fēng)
轉(zhuǎn)子選粉機(jī)，KXN型高效O-Sepa選粉機(jī)，KXZ型組合式選粉機(jī)，煤磨動(dòng)態(tài)選粉機(jī)，新SZGX型選粉機(jī)，新型高效雙轉(zhuǎn)子選粉機(jī)，新型空氣噴射型選粉機(jī)等。
科學(xué)依據(jù)（包括課題的科學(xué)意義；國(guó)內(nèi)外研究概況、水平和發(fā)展趨勢(shì)；應(yīng)用前景等）
選粉機(jī)是粉體作業(yè)中的粉體分級(jí)設(shè)備，與粉磨設(shè)備組成圈流粉磨系統(tǒng)，因此選粉機(jī)的工作質(zhì)量和工作效率對(duì)粉磨作業(yè)的效果有著直接的影響。本項(xiàng)設(shè)計(jì)是在國(guó)內(nèi)現(xiàn)有的旋風(fēng)式選粉機(jī)及O-SEPA選粉機(jī)的基礎(chǔ)上進(jìn)行改進(jìn)設(shè)計(jì)，主要是為了提高選粉機(jī)的選粉效率和對(duì)不同細(xì)度要求的適應(yīng)。以適應(yīng)不同水泥細(xì)度的球磨機(jī)粉磨系統(tǒng)的配套要求，以提高粉磨系統(tǒng)的產(chǎn)量，實(shí)現(xiàn)增產(chǎn)、節(jié)能的效果。
研究?jī)?nèi)容
在國(guó)內(nèi)現(xiàn)有的旋風(fēng)式選粉機(jī)及O-SEPA選粉機(jī)的基礎(chǔ)上進(jìn)行改進(jìn)設(shè)計(jì)，根據(jù)設(shè)計(jì)對(duì)象的工作原理分析進(jìn)行結(jié)構(gòu)及相關(guān)工作參數(shù)的分析，提出合理的設(shè)計(jì)方案、工作參數(shù)及結(jié)構(gòu)形式，進(jìn)行受力分析和強(qiáng)度計(jì)算等，能夠熟練運(yùn)用機(jī)械設(shè)計(jì)方面的手冊(cè)和查閱相關(guān)資料，能運(yùn)用二維和三維設(shè)計(jì)軟件繪制工程圖。
擬采取的研究方法、技術(shù)路線、實(shí)驗(yàn)方案及可行性分析
隨著建筑業(yè)的發(fā)展，以及水泥顆粒方面的研究，人們對(duì)水泥顆粒的要求也來(lái)也科學(xué)，同時(shí)對(duì)相應(yīng)的水泥工業(yè)的粉磨系統(tǒng)業(yè)提出了相應(yīng)的要求。粉磨系統(tǒng)由高能耗的開(kāi)路粉磨系統(tǒng)進(jìn)化到閉路粉磨系統(tǒng)，而作為閉路粉磨系統(tǒng)的一個(gè)重要的配套設(shè)備—選粉機(jī)也是經(jīng)過(guò)了三代的改進(jìn)。
選粉機(jī)雖然本身并無(wú)粉碎物料的作用，但其性能好壞直接影響到系統(tǒng)的運(yùn)行狀態(tài)，即影響到系統(tǒng)的粉磨效率、產(chǎn)量及能耗。因此，高效選粉機(jī)技術(shù)的研究具有重要意義。高效選粉機(jī)綜合性能好，但系統(tǒng)投資過(guò)大，而其他類型的選粉機(jī)性能又不很理想，特別是在生產(chǎn)比表面積350ｍ2/kg上水泥時(shí)效果比較差。本文重點(diǎn)研究的針對(duì)目前收塵設(shè)備投資較大，選粉室內(nèi)渦流不穩(wěn)等進(jìn)行對(duì)高效選粉機(jī)的改進(jìn)。
研究計(jì)劃及預(yù)期成果
研究計(jì)劃：
2012年11月12日-2012年12月25日：按照任務(wù)書(shū)要求查閱論文相關(guān)參考資料，填寫畢業(yè)設(shè)計(jì)開(kāi)題報(bào)告書(shū)。
2013年1月11日-2013年3月5日：填寫畢業(yè)實(shí)習(xí)報(bào)告。
2013年3月8日-2013年3月14日：按照要求修改畢業(yè)設(shè)計(jì)開(kāi)題報(bào)告。
2013年3月15日-2013年3月21日：學(xué)習(xí)并翻譯一篇與畢業(yè)設(shè)計(jì)相關(guān)的英文材料。
2013年3月22日-2013年4月11日：MATLAB程序設(shè)計(jì)。
2013年4月12日-2013年4月25日：GUI設(shè)計(jì)。
2013年4月26日-2013年5月21日：畢業(yè)論文撰寫和修改工作。
預(yù)期成果：
選粉室采用籠式轉(zhuǎn)子結(jié)構(gòu)，能有效地控制細(xì)度。
籠式轉(zhuǎn)子的導(dǎo)入，對(duì)粗顆粒能進(jìn)行多次撞擊，改善成品的顆粒級(jí)配。
延長(zhǎng)分級(jí)時(shí)間，選粉室的高度增加，增加了物料選粉的時(shí)間，又增加了旋風(fēng)筒的高徑比，增強(qiáng)了選粉機(jī)對(duì)十微米以下細(xì)粉的收集能力。
物料在分級(jí)室內(nèi)，在較強(qiáng)的旋流及徑向剪切力的作用下，物料分散性好且強(qiáng)度高，分級(jí)效率高。
分選物料都經(jīng)過(guò)分級(jí)界面分明的選粉區(qū)，各部分的選粉條件穩(wěn)定，故選粉機(jī)的分級(jí)精度高。
細(xì)度調(diào)節(jié)方便可靠，且調(diào)節(jié)范圍較寬，可通過(guò)調(diào)節(jié)主軸轉(zhuǎn)速及風(fēng)量靈活控制。
可使開(kāi)流磨增產(chǎn)40-60%，選粉效率可達(dá)85%以上。
在相同產(chǎn)量的情況下，與高效渦流式選粉機(jī)相比效率相當(dāng)，但可降低系統(tǒng)投資20-30%；與旋風(fēng)式及高效離心式選粉機(jī)相比，不但可減少設(shè)備規(guī)格，并可提高效率20-40%。
特色或創(chuàng)新之處
本設(shè)計(jì)收塵設(shè)備改為旋風(fēng)筒收塵，并對(duì)旋風(fēng)筒進(jìn)行了改進(jìn)以提高收塵效果。殼體設(shè)計(jì)中去掉了二次和三次風(fēng)，并調(diào)整了一次風(fēng)的位置以得到穩(wěn)定的渦流。
已具備的條件和尚需解決的問(wèn)題
已具備的條件：電腦；相關(guān)開(kāi)發(fā)軟件；部分技術(shù)資料。
尚需解決的問(wèn)題：學(xué)習(xí)UG軟件；確定產(chǎn)品的結(jié)構(gòu)尺寸和技術(shù)要求；逆向設(shè)計(jì)建立三維數(shù)模；總成運(yùn)動(dòng)仿真校核。
指導(dǎo)教師意見(jiàn)
指導(dǎo)教師簽名：
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教研室（學(xué)科組、研究所）意見(jiàn)
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英文譯文
tape transport
Among the methods of material conveying quantity, belt conveyors play a very important part in the reliable carrying of material over long distances at competitive cost. Conveyor systems have become larger and more complex and drive systems have a l so been going through a process of evolution and will continue to do so. Nowadays, bigger belts require more power and have brought the need for larger individual drives as well as multiple drives such as 3 drives of 750 kW for one belt(this is the case for the conveyor drives in Chengzhuang Mine). The ability to control drive acceleration torque is critical to belt conveyors' performance. A efficient drive system should be able to provide smooth, soft starts while maintaining belt tensions within the specified safe limits. For load sharing on multiple drives. torque and speed control are also considerations in the drive system's design. Due to the advances in conveyor drive control technology, at present many more reliable. Cost-effective and performance- driven conveyor drive systems covering a wide range of power are available for customers' choices[1].
1 tape transport on conveyor drive technologies
1. 1 The belt transmission mode
Full-voltage starters. With a full-voltage starter design, the conveyor
head shaft is direct-coupled to the motor through the gear drive. Direct
full-voltage starters are adequate for relatively low-power, simple- Profile conveyors. With direct full-voltage starters. no control is provided for various conveyor loads and. depending on the ratio between full- and no-load power requirements, empty starting times can be three or four times faster than full load. The maintenance-free starting system is simple, low-cost and very reliable. However, they cannot control starting torque and maximum stall torque; therefore. they are limited to the low-power, simple-profile conveyor belt drives.
Reduced-voltage starters. As conveyor power requirements increase,controlling the applied motor torque during the acceleration period becomes increasingly important. Because motor torque is a function of voltage, motor voltage must be controlled. This can be achieved through reduced-voltage starters by employing a silicon controlled rectifier (SCR). A common starting method with SCR reduced-voltage starters is to apply low voltage initially to take up conveyor belt slack. and then to apply a timed linear ramp up to full voltage and belt speed. However, this starting method will not produce constant conveyor belt acceleration. When acceleration is complete. the SCRs, which control the applied voltage to the electric motor. are locked in full conduction, providing full-line voltage to the motor. Motors with higher torque and pull -vp torque, can provide better starting torque when combined with the SCR starters, which are available in sizes up to 750 KW.
Wound rotor induction motors. Wound rotor induction motors are
connected directly to the drive system reducer and are a modified configuration of a standard AC induction motor. By inserting resistance in series with the motor's rotor windings. the modified motor control System controls motor torque. For conveyor starting, resistance is placed in series with the rotor for low initial torque. As the conveyor accelerates,the resistance is reduced slowly to maintain a constant acceleration torque. On multiple-drive systems. an external slip resistor may be left in series with the rotor windings to aid in load sharing .the motor systems have a relatively simple a design.However,the control systems for these can be highly complex, because they are based on computer control of the resistance switching. Today, the majority of control systems are custom designed to meet a conveyor system's particular specifications. Wound rotor motors are appropriate for systems requiring more than 400KW.
DC motor. DC motors. available from a fraction of thousands of KW，are designed to deliver constant torque below base speed and constant KW above base speed to the maximum allowable revolutions per minute (r/min). with the majority of conveyor drives, a .DC shunt wound motor is used. Wherein the motor's rotating armature is connected externally. The most common technology for controlling DC drives is a SCR device. which allows for continual variable-speed operation. The DC drive system is mechanically simple, but can include complex custom-designed electronics to monitor and control the complete system. this system option is expensive in comparison to other soft-start systems. but it is a reliable, cost-effective drive in applications in which torque,load sharing and variable speed are primary considerations. DC motors generally are used with higher-power conveyors, including complex profile conveyors with multiple-drive systems, booster tripper systems needing belt tension control and conveyors requiring a wide variable-speed range.
1. 2 Hydrokinetic coupling
Hydrokinetic couplings, commonly referred to as fluid couplings. are composed of three basic elements; the driven impeller, which acts as a
centrifugal pump; the driving hydraulic turbine known as the runner and
a casing that encloses the two power components. Hydraulic fluid is pumped from the driven impeller to the driving runner, producing torque at the driven shaft. Because circulating hydraulic fluid produces the torque and speed, no mechanical connection is required between the driving and driver shafts.The power produced by this coupling is based on the circulated fluid's amount and density and the torque in proportion to input speed. Because the pumping action within the fluid coupling depends on centrifugal forces. the output speed is less than the input speed. Referred to as slip. this normally is between 1% and 3%. Basic hydrokinetic couplings are available in configurations from fractional to several thousand KW.
Fixed-fill fluid couplings. Fixed-fill fluid couplings are the most commonly used soft-start devices for conveyors with simpler belt profiles and limited convex/concave sections. They are relatively simple,low-cost,reliable,maintenance free devices that provide excellent soft starting results to the majority of belt conveyors in use today.
Variable-fill drain couplings. Drainable-fluid couplings work on the same principle as fixed-fill couplings. The coupling's impellers are mounted on the AC motor and the runners on the driven reducer high-speed shaft. Housing mounted to the drive base encloses the working circuit. The coupling's rotating casing contains bleed-off orifices that continually allow fluid to exit the working circuit into a separate hydraulic reservoir. Oil from the reservoir is pumped through a heat exchanger to a solenoid-operated hydraulic valve that controls the filling of the fluid coupling. To control the starting torque of a single-drive conveyor system, the AC motor current must be monitored to provide feedback to the solenoid control valve. Variable fill drain couplings are used in medium to high-kw conveyor systems and are available in sizes up to thousands of kw.The drives can be mechanically complex and depending on the control parameters. the system can be electronically intricate. The drive system cost is medium to high,depending upon size specified.
Hydrokinetic scoop control drive. The scoop control fluid coupling consists of the three standard fluid coupling components: a driven impeller, a driving runner and a casing that encloses the working circuit. The casing is fitted with fixed orifices that bleed a predetermined amount of fluid into a reservoir. When the scoop tube is fully extended into the reservoir, the coupling is 100 percent filled. The scoop tube, extending outside the fluid coupling, is positioned using an electric actuator to engage the tube from the fully retracted to the fully engaged position. This control provides reasonably smooth acceleration rates. to but the computer-based control system is very complex. Scoop control couplings are applied on conveyors requiring single or multiple drives from 150KWto 750KW.
1. 3 Variable-frequency control(VFC)
Variable frequency control is also one of the direct drive methods. the emphasizing discussion about it here is because that it has so unique characteristic and so good performance compared with other driving methods for belt conveyor. VFC devices Provide variable frequency and voltage to the induction motor, resulting in an excellent starting torque and acceleration rate for belt conveyor drives. VFC drives. available from fractional to several thousand (kW)，are electronic controllers that rectify AC line power to DC and, through an inverter, convert DC back to AC with frequency and voltage control. VFC drives adopt vector control or direct torque control(DTC)technology, and can adopt different operating speeds according to different loads. VFC drives can make starting or stalling according to any given S-curves realizing the automatic track for starting or stalling curves. VFC drives provide excellent speed and torque control for starting conveyor belts. and can also be designed to provide load sharing for multiple drives. easily VFC controllers are frequently installed on lower-powered convey- or drives, but when used at the range of medium-high voltage in the past. the structure of VFC controllers becomes very complicated due to the limitation of voltage rating of power semiconductor devices, the combination of medium-high voltage drives and variable speed is often solved with low-voltage inverters using step-up transformer at the output, or with multiple low-voltage inverters connected in series. Three-level voltage-fed PWM converter systems are recently showing increasing popularity for multi-megawatt industrial drive applications because of easy voltage sharing between the series devices and i叩roved harmonic quality at the output compared to two-level converter systems With simple series connection of devices. This kind of VFC system with three 750 kW /2. AV inverters has been successfully installed in ChengZhuang Mine for one 2. 7-km long belt conveyor driving system in following the principle of three-level inverter will be discussed in detail.
2 Neutral point clamped(NPC)three-level inverter using IGBT
Three-level voltage-fed inverters have recently become more and more popular for higher power drive applications because of their easy voltage sharing features. lower dv / dt per switching for each of the devices, and super or harmonic quality at the output. The availability of NV-IGBT
has led to the design of a new range of medium-high voltage inverter using three-level NPC topology. This kind of inverter can realize a whole range with a voltage rating from 2. 3 kV to 4. 1 6kV Series connection of IIV-IGBT modules is used in the 3. 3 kV and 4. 1 6kV devices. The 2. 3 kV inverters need only one HV-IGBT per switch[2,3].
2. 1 Power section
To meet the demands for medium voltage applications. a three-level
neutral point clamped inverter realizes the power section. In comparison
to a two-level inverter. the NPC inverter offers the benefit that three voltage levels can be supplied to the output terminals, so for the same output current quality, only 1/4 of the switching frequency is necessary. Moreover the voltage ratings of the switches in NPC inverter topology will be reduced to 1/2. and the additional transient voltage stress on the motor can also be reduced to 1/2 compared to that of a two-level inverter.
The switching states of a three-level inverter are summarized in Table 1. U. V and W denote each of the three phases respectively; P N and 0 are the do bus points. The phase U, for example, is in state P (positive bus voltage)when the switches S1uand S2u are closed, whereas it is in state N (negative bus voltage) when the switches S3u and S4u, are closed. At neutral point clamping, the phase is in 0 state when either S2u.or S3u, conducts depending on positive or negative phase current polarity, respectively. For neutral point voltage balancing, the average current injected at 0 should be zero.
2. 2 Line side converter
For standard applications. a 12-pulse diode rectifier feeds the divided DC-link capacitor. This topology introduces low harmonics on. the line side. For even higher requirements a 24-pulse diode rectifier can be used as an input converter. For more advanced applications where regeneration. capability is necessary, an active front. end converter can replace the diode rectifier, using the same structure as the inverter.
2. 3 Inverter control
Motor Control. Motor control of induction machines is realized by
using a rotor flux. oriented vector controller.
Fig. 2 shows the block diagram of indirect vector controlled drive that incorporates both constant torque and high speed field-weakening regions where the PW M modulator was used. In this figure, the command fluxψ.is generated as function of speed. The feedback speed is added with the feed forward slip command signalψ,the resulting frequency signal is integrated and then the unit vector signals(cosθe and sinθ e)are generated. The vector rotator generates the voltage Vs and Angle θe commands for the PW M as shown.
PWM Modulator. The demanded voltage vector is generated using an elaborate PWM modulator. The modulator extends the concepts of space-vector modulation to the three-level inverter. The operation can be
explained by starting from a regularly sampled sine-triangle comparison
from two-level inverter. Instead of using one set of reference waveforms
and one triangle defining the switching frequency, three-level Modulator uses two sets of reference waveforms U and U and just one triangle. Thus, each switching transition is used in an optimal way so that several objectives are reached at the same time.
Very low harmonics are generated. The switching frequency is low and thus switching losses are minimized. As in a two-level inverter, a zero-sequence component can be added to each set of reference waveform s in order to maximize the fundamental voltage component. As an additional degree of freedom, the position of the reference waveform s within the triangle can be changed. This can be used for current balance in the two halves of the DC-link.
3 Testing results
After Successful installation of three 750 kW /2. 3 kV three-level
inverters for one 2. 7 km long belt conveyor driving system in Cheng
zhuang Mine. The performance of the whole VFC system was tested. Fig. 3 is taken from the test, which shows the excellent characteristic of the belt conveyor driving system with VFC controller.
Fig. 3 includes four curves. The curve 1 shows the belt tension . From the curve it can be find that the fluctuation range of the belt tension is very small. Curve 2 and curve 3 indicate current and torque separately. Curve 4 shows the velocity of the controlled belt. The belt velocity have the "s" shape characteristic. All the results of the test show a very satisfied characteristic for belt driving system.
4 Conclusions
Advances in conveyor drive control technology in recent years have
resulted in many more reliable. Cost-effective and performance-driven conveyor drive system choices for users.Among these choices,the Variable frequency control (VFC) method shows promising use in the future for long distance belt conveyor drives due to its excellent performances. The NPC three-level inverter using high voltage TGBT make the Variable frequency control in medium voltage applications become much more simple because the inverter itself can provide the medium voltage needed at the motor terminals, thus eliminating the step-up transformer in most applications in the past. The testing results taken from the VFC control system with NTC three. level inverters used in a 2. 7 km long belt conveyor drives in Chengzhuang Mine indicates that the performance of NPC three-level inverter using HV-TG
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