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河南理工大學(xué)萬方科技學(xué)院本科生英文翻譯
____________________________________________________________________________________________
本科畢業(yè)設(shè)計(jì)（論文）
中英文對(duì)照翻譯
院（系部） 萬方科技學(xué)院機(jī)械與動(dòng)力工程系
專業(yè)名稱 機(jī)械設(shè)計(jì)及其自動(dòng)化
年級(jí)班級(jí) 機(jī)制08-2班
學(xué)生姓名 史 銳
指導(dǎo)老師 閆艷燕
2012年5月
Belt conveying systems development of driving system
FU Jun-qing; WANG Cong; HUO Wei (Department of Information and Electrical Engineering; China University of Mining & Technology (Beijing) Beijing 100083; China);
Among the mothods of material conveing employed, belt conveyors play a very important part in the reliable carrying of material over long distancees at competitive cost. Conveyor systems have become larger and more conplex and drive systems have also 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 KWfor one belt (this is the case for the conveyor drives in chengzhuang mine0. The ability to control drive acceleration toque is critical to belt conveyors performance. An efficednt 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 important considerations in the drive syetens design. Due to the advances in conveyor drice control technology, at present many more reliable. COST-effective and peerformance-driven conveyor drive systems covering a wide range of power are available for customer'choices.
1 Analysis on conveyor drive technologies
1.1 Direct drives
Full-voltage stsrters. With a full voltage stsrter design, the conveyor hesd 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- votage startersnocontrol is provided for various conveyor loads and. Depending on the radio between full and no load power requirements,emty starting times can be three or four times faster than full load. The maintennance-free staring system is simpke, low-cost and very reliable, however,they cannot control starting torque and maximum stall torque:therefore,they are limited to the low-ower, simple-profile conveyor belt drives.
Reduced-voltage starters, As conveyor power requirement 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. 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 acceleration. When acceleration is complete. The SCRS,which control the appareled voltage to the electric motor. Are locked in full conduction, providing full-line voltage to the motor. Motor with higher torque and pull up torque can provide better staring torque when combined with the SCR which are available in sizes up to 750kw .
Wound rotor induction motors, wound rotor induction motors are connected directly to the drive system reducer and are a modified configurate of a standard AC induction motor . By inserting resistance in series with the motors 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 accelerating torque. On multiple-drive systems. An external slip resistor maybe left in series with the motor windings aid in load sharing. The motor systems have a relatively simple design. However, the control system for these can be highly complex,because they are based on computer control of the resistance switching. Today, because they are based on computer control of the resistance switching. Today, the majority of control systems are custom designed to meet a conveyor systems particular specifications. Wound rotor motors are appropriate for systems requiring more than 400 kw .
DC motor . Dc motor,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. With the majority of conveyor drives, a dc shunt wound motor is used. Wherein the motors 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 Germanically simple, but can include complaining custom -designed electronics to monitor and control the compel 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 systems needing belt tension control and conveyors requiring a wide variable-speed range.
1.2 hydromagnetic coupling
Hydromagnetic couplings, commonly referred to as fluid couplings, are composed of three basic elements; the driven compelled,witch acts as a centrifugal pump; the driving hydraulic turbine known as the runner and a casing that encloses the two power comments. Hydromagnetic fluid is pumped from driven impeller to the driving runner, producing torque and speed, no mechanical connection is required between the driving and driven shafts. The power produced by this coupling is based on the circulated fluids amount and density and the torque in proportion to input sheet. 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.are the most commonly used soft devices for conveyor with simpler belt profiles and limited convex 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 di ain couplings. Drainable-Fula couplings work on the same principle an pixed-fill couplings. The couplings.impellers moated on the ac motor and the dinners on the driven reducer high-speed shaft . Housing moated ti the drive base encloses the working circuit. The couplings rotating casing contains bleed off orifices that Continental allow fluid to exit the working circuit into a separate hydraulic reservoir oil from the reservoir is fumed through heat exchanger to a soled-operated hydraulic valve that controls the filling go the fluid coupling. To control the staring 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 affricate . 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 bleed a predetermined about of fluid into a reservoir. When the filled. The scoop tube,centering outside the fluid coupling,is 100 percent filled. The scoop tube, extending outside the fluid coupling, is positioned using an electric actuator to Edgefield the tube from the fully reacted 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 150 kw to 750 kw .
1.3 Variable-frequency control
Variable-frequency control is also one of the direct dict drive Methods. Ate emphasizing discussion about it here is because that it has so unique characteristic and so good affirmance compared with other driving methods for belt conveyor. Pfc devices provide variable frequency and cabotage to the induction motor,resulting in an excellent staring torque to the induction motor,resisting in an Excellence starting torque and acceleration rate for belt conveyor drives. Pfc drives, available from fractional to several thousand, are electronic controllers that rectify and voltage control. Pfc drives adopt vector control or direct torque Cantrall technology , and can adopt different operating speeds according to different loads , Pfc drives can make starting or stalling according to any given s-curves, realizing the automatic track for starting or stalling curves. Pfc drives provide excellent speed and torque control for starting con conveyor belts. And can also be designed to provide load sharing for multiple drives, easily Pfc controllers are frequently installed on lower-powered conveyor drives,but when used at the range of medium-high voltage in the past. The structure of Pfc controllers becomes very complicated due to the limitation of voltage rating of
Power semiconductor devices,the combination of medium-h ign 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 using step-up transformer at the output, or with multiple low -voltage inverters connected in series . Three-level voltage-fed cwm conveyor systems are recently showing increasing popularity for culti-megawatt industrial drive applications because of easy voltage sharing between the series devices and improved harmonic quality at the output compared to two level converter systems with simple series connection of devices. This kind of Pfc system with three 750inverters has been successfully installed in Zhengzhou 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 three-level inverter using 1GBTs
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 per switching for each of the Devereux, and super or harmonic quality at the output. The availability of av-bigots has led to the design of a new range of medium-high voltage inverter using tare-level Np topology . This king of inverter can irrealizable a whole range with a voltage eating from 2.3 iv to 4.16kv connectionism of av-Sgt modules is used in the 3.3kv and 4.1 devices.the .3 iv inverters need only one av-Igbos per switch.
2.1power 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 Np inverter offers beneficent 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 Voltaire 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 i.u.v and w denote each of the three phases respectively; pn and 0 are the dc bus points. The phase u , for example, whereas it is in state n when the switches S1u and S2u are closed. At neutral point clamping , the phase is in 0 state when either S2u or S3 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-lnk capacitor. This topology introduces low harmonices 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 font , en d converter can replace the diode rectifier,using the same structure as the inverter.
2.3 inverter control
Motor control of induction machines is realized by using a rotor flux . Oriented vector controller.
Fig,1
Fig,1shows the block diagram of indirect vector controlled drive that incorporates both constant torque and high speed field-weakening regions where the PM W modulator was used. In this figure, the command flux is generated as function of speed. The feedback speed is added with the feed forward slip command signal,the resulting frequency signal is integrated and then the unt vector signals are generated. The vector rotator generates the voltage V and angle @c commands for the PW M as shown.
PW M modulator. The demanded voltage vector is generated using an elaborate PW M modulator..the modulator extends the concepts of space-vector modulator to the three-level inverter.the operation can be explained by staring 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, the three-level modulator uses two sets of reference waveform Ur1 and Ur2 and just one treangle. 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 maximze the fundamental voltage component . As an additional degree of freedom, the position of the reference waveforms within the triangle can be changed . This can bi used for current balance in the halves of the DC-link
3 testing results
After successful installation of three 750 kw three-level incerters for one 2.7 kw long belt conveyor driving system in chengzhuang 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 2
Fig 2 includes four curves . The curve 1 show 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 method shows promising use in the future for long distance belt conveyor drives due to its excellent performance. The NPC three-level inverter using high voltage IGBTs make the variable frequency control in medium applications become much mare 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 NPC three. Level inverters used in a 2.7 km long belt conveyor drives in Cchengzhuang mine indicates that the performance of NPCthree-level inverter using HV-IGBTS together with the control strategy of rotor field-oriented vector control for induction motor drive is excellent for belt conveyor driving system.
帶式輸送機(jī)傳動(dòng)系統(tǒng)的發(fā)展
富放射；王聰；霍?。ㄐ畔⑴c電子工程系；中國礦業(yè)大學(xué)科技（北京）北京100083；中國）
在運(yùn)送大量的物料時(shí)，帶式輸送機(jī)在長距離的運(yùn)輸中起到了非常重要的競爭作用。輸送系統(tǒng)將會(huì)變得更大、更復(fù)雜，而驅(qū)動(dòng)系統(tǒng)也已經(jīng)歷了一個(gè)演變過程，并將繼續(xù)這樣下去。如今，較大的輸送帶和多驅(qū)動(dòng)系統(tǒng)需要更大的功率,比如3驅(qū)動(dòng)系統(tǒng)需要給輸送帶750KW (成莊煤礦輸送機(jī)驅(qū)動(dòng)系統(tǒng)的要求)?？刂乞?qū)動(dòng)力和加速度扭矩是輸送機(jī)的關(guān)鍵。一個(gè)高效的驅(qū)動(dòng)系統(tǒng)應(yīng)該能順利的運(yùn)行,同時(shí)保持輸送帶張緊力在指定的安全極限負(fù)荷內(nèi)。為了負(fù)載分配在多個(gè)驅(qū)動(dòng)上，扭矩和速度控制在驅(qū)動(dòng)系統(tǒng)的設(shè)計(jì)中也是很重要的因素。由于輸送機(jī)驅(qū)動(dòng)系統(tǒng)控制技術(shù)的進(jìn)步,目前更多可靠的低成本和高效驅(qū)動(dòng)的驅(qū)動(dòng)系統(tǒng)可供顧客選擇。
1輸送機(jī)驅(qū)動(dòng)技術(shù)分析
1.1直接驅(qū)動(dòng)
一個(gè)完整的電壓驅(qū)動(dòng)設(shè)計(jì)，輸送機(jī)機(jī)頭軸直接耦合到電機(jī)通過齒輪傳動(dòng)。直接全壓起動(dòng)是足夠的相對(duì)低功耗，直接全電壓提供各種輸送機(jī)負(fù)荷。根據(jù)不同的電臺(tái)之間的充分和無負(fù)載功率的要求，早期開始的時(shí)間可以是三或四倍的速度比全負(fù)荷。該驅(qū)動(dòng)凝視系統(tǒng)是雙端彎曲，低成本和可靠的，但是，他們無法控制的起動(dòng)轉(zhuǎn)矩和最大扭矩：因此，他們是有限的輸送皮帶驅(qū)動(dòng)。
降壓起動(dòng)器，如輸送電力需求的增長，控制應(yīng)用力矩電機(jī)在加速期間變得越來越重要。由于電動(dòng)機(jī)的扭矩是一個(gè)函數(shù)的電壓，電機(jī)電壓控制。這可以通過降壓起動(dòng)器采用可控硅整流器。一個(gè)有效方法可控硅降壓起動(dòng)器適用低電壓最初采取了輸送帶松弛。然后應(yīng)用線性斜坡上定時(shí)全電壓帶加速度。當(dāng)加速完成?？煽毓杩刂疲瑧?yīng)用電壓電動(dòng)機(jī)。被鎖在全傳導(dǎo)，提供全系列電壓的電動(dòng)機(jī)。電機(jī)具有較高的轉(zhuǎn)矩和最小轉(zhuǎn)矩可以提供更好的起動(dòng)轉(zhuǎn)矩結(jié)合晶閘管，可滿足尺寸水平的要求。
繞線轉(zhuǎn)子感應(yīng)電動(dòng)機(jī)，繞線轉(zhuǎn)子感應(yīng)電動(dòng)機(jī)直接連接到驅(qū)動(dòng)系統(tǒng)減速器和修改標(biāo)準(zhǔn)交流感應(yīng)電機(jī)。插入串聯(lián)電阻與電機(jī)轉(zhuǎn)子繞組的電機(jī)控制系統(tǒng)，控制電動(dòng)機(jī)的轉(zhuǎn)矩。用于輸送機(jī)啟動(dòng)，抵抗是放置在與轉(zhuǎn)子低初始轉(zhuǎn)矩。為加速阻力降低，慢慢地保持恒定的扭矩。在多重驅(qū)動(dòng)系統(tǒng)。外部滑動(dòng)電阻也許在一系列與轉(zhuǎn)子繞組在負(fù)載共享。電機(jī)系統(tǒng)有一個(gè)相對(duì)簡單的設(shè)計(jì)。然而，控制系統(tǒng)可以更復(fù)雜，因?yàn)樗鼈兪腔谟?jì)算機(jī)控制的電阻開關(guān)。今天，因?yàn)樗麄兪歉鶕?jù)計(jì)算機(jī)控制的電阻開關(guān)。今天，大多數(shù)控制系統(tǒng)是定制設(shè)計(jì)滿足特定規(guī)格的輸送系統(tǒng)。繞線式電機(jī)適合系統(tǒng)需要超過400千瓦。
直流電機(jī)，可從一個(gè)分?jǐn)?shù)萬千瓦，旨在提供以下恒轉(zhuǎn)矩和恒功率速度高于額定轉(zhuǎn)速到最大允許每分鐘轉(zhuǎn)數(shù)。與大多數(shù)輸送機(jī)驅(qū)動(dòng)器，直流復(fù)勵(lì)電機(jī)。其中，馬達(dá)旋轉(zhuǎn)電樞連接外部。最常見的技術(shù)用于控制直流驅(qū)動(dòng)器是一個(gè)可控硅整流裝置。可連續(xù)變速運(yùn)行。直流驅(qū)動(dòng)系統(tǒng)是最簡單的，但可以包括綜合定制設(shè)計(jì)的電子監(jiān)測(cè)和控制系統(tǒng)的完善。該系統(tǒng)的選擇是昂貴的相對(duì)于其他軟啟動(dòng)系統(tǒng)。但它是一個(gè)可靠的，高性價(jià)比的傳動(dòng)應(yīng)用中，轉(zhuǎn)矩，負(fù)載共享和變速是首要的考慮問題。直流電動(dòng)機(jī)一般采用高次輸送機(jī)，包括復(fù)雜的文件傳送帶多重驅(qū)動(dòng)系統(tǒng)，增壓系統(tǒng)的需要，皮帶張力控制和輸送需要一個(gè)廣泛的變速范圍。
1.2磁流體耦合
磁流耦合，通常稱為流體聯(lián)軸器，是由三個(gè)基本要素構(gòu)成；驅(qū)動(dòng)系統(tǒng)，作為離心泵；驅(qū)動(dòng)水輪機(jī)稱為亞軍和一個(gè)外殼包圍的功率成分。磁流體液體從泵驅(qū)動(dòng)葉輪驅(qū)動(dòng)轉(zhuǎn)輪，產(chǎn)生轉(zhuǎn)矩和速度，無機(jī)械連接是需要的驅(qū)動(dòng)和驅(qū)動(dòng)軸。電力生產(chǎn)的這種耦合是基于循環(huán)液量和密度和扭矩比例輸入轉(zhuǎn)速。由于泵的作用在流體耦合取決于離心力。輸出速度小于輸入速度。稱為滑移。這通常是1%和3%?；疽毫β?lián)軸器可在配置從分?jǐn)?shù)到幾千瓦。
固定流體聯(lián)軸器是最常用的軟設(shè)備，簡單帶概況和有限的凸部分。他們是相對(duì)簡單的，低成本，可靠，免維護(hù)設(shè)備，提供優(yōu)良的軟啟動(dòng)的結(jié)果，大多數(shù)帶式輸送機(jī)在使用今天。
多變聯(lián)軸器與排空聯(lián)軸器的工作原理是一樣的聯(lián)軸器。該類聯(lián)軸器安裝在交流電機(jī)和減速器高速軸上的驅(qū)動(dòng)系統(tǒng)。房屋安裝鈦驅(qū)動(dòng)包圍基地工作電路。聯(lián)軸器旋轉(zhuǎn)外殼包含泄放口，不斷使流體退出工作電路成為一個(gè)獨(dú)立的液壓油從水庫通過熱交換器，一個(gè)液壓閥控制液體灌裝去耦合。控制起動(dòng)轉(zhuǎn)矩的單一驅(qū)動(dòng)輸送系統(tǒng)交流電動(dòng)機(jī)電流進(jìn)行監(jiān)測(cè)，提供反饋到控制的電磁閥。變填補(bǔ)排水聯(lián)軸器用于介質(zhì)高千瓦輸送系統(tǒng)，可在尺寸上千千瓦。驅(qū)動(dòng)器可以機(jī)械地復(fù)雜，在不同的控制參數(shù)。該系統(tǒng)可以電子驅(qū)動(dòng)。驅(qū)動(dòng)系統(tǒng)成本中高，這取決于所指定的大小。
流體動(dòng)力鏟控制驅(qū)動(dòng)器，勺控制流體耦合由三標(biāo)準(zhǔn)液耦合元件：葉輪驅(qū)動(dòng)，驅(qū)動(dòng)轉(zhuǎn)輪和外殼，預(yù)定量流血流體成藏。當(dāng)填充，勺管外，流體耦合，滿是百分之百。導(dǎo)管，外延伸，流體耦合，定位使用電動(dòng)致動(dòng)器導(dǎo)管從完全充分參與的立場(chǎng)。這種控制提供合理順暢的加速率。但計(jì)算機(jī)控制系統(tǒng)是非常復(fù)雜的。勺控制聯(lián)軸器適用于輸送需要單個(gè)或多個(gè)驅(qū)動(dòng)器從150千瓦到750千瓦。
1.3變頻控制
變頻控制也是一個(gè)直接驅(qū)動(dòng)技術(shù)。興田強(qiáng)調(diào)討論關(guān)于它在這里是因?yàn)樗歇?dú)特的特點(diǎn)，所以良好的性能權(quán)衡與其他驅(qū)動(dòng)方法的帶式輸送機(jī)。變頻控制設(shè)備提供可變頻率和電壓的感應(yīng)電機(jī)，產(chǎn)生良好的起動(dòng)轉(zhuǎn)矩的電機(jī)，目的在于證明起動(dòng)轉(zhuǎn)矩和加速度為帶式輸送機(jī)驅(qū)動(dòng)器。變頻控制驅(qū)動(dòng)器，可從分?jǐn)?shù)到幾千，電子控制器，整頓和電壓控制。變頻控制驅(qū)動(dòng)器采用矢量控制和直接轉(zhuǎn)矩控制技術(shù)，可以采用不同的運(yùn)行速度可根據(jù)不同的載荷，動(dòng)態(tài)驅(qū)動(dòng)器可以啟動(dòng)或停止任何根據(jù)S曲線，實(shí)現(xiàn)自動(dòng)啟動(dòng)或停止跟蹤曲線。變頻控制驅(qū)動(dòng)器提供出色的速度和轉(zhuǎn)矩控制啟動(dòng)控制輸送帶。也可以設(shè)計(jì)為負(fù)載共享的多個(gè)驅(qū)動(dòng)器，容易式控制器安裝在輸送機(jī)常較小，但使用時(shí)，在高電壓范圍在過去。結(jié)構(gòu)式控制器變得非常復(fù)雜，由于限制電壓額定值。
功率半導(dǎo)體器件，結(jié)合電壓驅(qū)動(dòng)器和可變速度一般采用低壓變頻器采用升壓變壓器的輸出，或多個(gè)低壓變頻器采用升壓變壓器的輸出，或多個(gè)低電壓逆變器系列。三電平電壓型脈寬調(diào)制輸送系統(tǒng)是最近表現(xiàn)出日益普及的兆瓦級(jí)工業(yè)驅(qū)動(dòng)應(yīng)用由于易于電壓之間分享系列設(shè)備和改進(jìn)諧波質(zhì)量的輸出電平轉(zhuǎn)換器系統(tǒng)比較簡單的串接裝置。這種變頻控制系統(tǒng)，已成功安裝在成莊帶式輸送機(jī)的一個(gè)2.7公里長的帶式輸送機(jī)驅(qū)動(dòng)系統(tǒng)，在以下的原則，三電平逆變器將詳細(xì)討論。
2系統(tǒng)動(dòng)力
2.1動(dòng)力
動(dòng)力要滿足需求中的應(yīng)用，三電平中點(diǎn)箝位逆變器實(shí)現(xiàn)功率部分。在比較兩級(jí)逆變器。該逆變器提供的利益，三個(gè)電壓水平可以提供給輸出端子，使輸出電流相同的質(zhì)量，只有1 /4的開關(guān)頻率是必要的。此外，系統(tǒng)開關(guān)的逆變器拓?fù)鋵p少到1/ 2。和其他瞬態(tài)電壓應(yīng)力對(duì)電機(jī)也可以減少到1/2相比，兩級(jí)逆變器。
三電平逆變器的開關(guān)狀態(tài)，總結(jié)在表i.u.v和瓦特表示三個(gè)階段分別；營養(yǎng)和0直流母線點(diǎn)。你的階段，例如，而這是在狀態(tài)，當(dāng)開關(guān)s1u和s2u關(guān)閉。在中性點(diǎn)箝位，相位在0狀態(tài)時(shí)，無論是s2u或三行為取決于積極或消極的相電流極性，分別。中性點(diǎn)電壓平衡，平均電流注入量應(yīng)該是零。
2.2線側(cè)變換器
標(biāo)準(zhǔn)應(yīng)用的12脈波整流二極管，電容分多種類型。這種拓?fù)浣榻B低在線路側(cè)。甚至更高的要求，一個(gè)24脈波整流二極管可以作為輸入轉(zhuǎn)換器。更先進(jìn)的應(yīng)用，再生能力是必要的，一個(gè)活躍的字體，在轉(zhuǎn)換器可以代替二極管整流器，逆變器使用相同的結(jié)構(gòu)。
2.3逆變器控制
電機(jī)控制的感應(yīng)電機(jī)采用轉(zhuǎn)子磁場(chǎng)。導(dǎo)向矢量控制器。
圖1.
圖1.顯示了框圖間接矢量控制驅(qū)動(dòng)系統(tǒng)，采用恒定扭矩和高速弱磁區(qū)，下端瓦特調(diào)制器是用來調(diào)節(jié)速度。在這個(gè)數(shù)字，命令產(chǎn)生磁通量功能的速度。反饋速度加前饋滑命令信號(hào)，所產(chǎn)生的高頻信號(hào)集成和隨后的向量信號(hào)產(chǎn)生。矢量旋轉(zhuǎn)產(chǎn)生的電壓和角度-命令一樣顯示密碼。
米調(diào)制器，要求電壓矢量是利用一個(gè)精心私服米調(diào)制器的調(diào)制器的概念擴(kuò)展空間矢量調(diào)制器的三級(jí)替換操作可以解釋從定期采樣例子比較級(jí)逆變器。而不是使用一套參考波形和一個(gè)三角形定義的開關(guān)頻率，三電平調(diào)制器采用2套參考波形ur1和ur2和一個(gè)參照。因此，每個(gè)開關(guān)過渡使用的最佳方式使多個(gè)目標(biāo)同時(shí)達(dá)到。
低諧波的產(chǎn)生，開關(guān)頻率低，開關(guān)損耗最小化。作為一級(jí)逆變器，一零序分量可以被添加到每一套參考波形為最大基本電壓分量。作為一個(gè)額外的自由度，位置參考波形的三角形內(nèi)是可以改變的。這可用于電流平衡在半直流。
3測(cè)試結(jié)果
安裝成功后三個(gè)750千瓦級(jí)，一個(gè)2.7千瓦的長距離帶式輸送機(jī)驅(qū)動(dòng)系統(tǒng)在成莊礦用帶式輸送機(jī)。整體性能的變頻控制系統(tǒng)的測(cè)試。圖3是從試驗(yàn)，這表明的優(yōu)良特性，傳動(dòng)系統(tǒng)由變頻控制控制器。
圖2.
圖2.包括四個(gè)曲線。曲線1表明皮帶張力。從曲線圖可以發(fā)現(xiàn)，波動(dòng)的皮帶張力很松，2和3分別表示電流和轉(zhuǎn)矩曲線。4顯示曲線速度的控制帶。帶速的形狀特征。所有試驗(yàn)結(jié)果表明一個(gè)非常滿意的特點(diǎn)為皮帶傳動(dòng)系統(tǒng)。
4結(jié)論
輸送機(jī)驅(qū)動(dòng)控制技術(shù)的進(jìn)步，近年來已導(dǎo)致更多的可靠的。成本-有效和驅(qū)動(dòng)的傳送帶驅(qū)動(dòng)系統(tǒng)供用戶選擇。在這些選擇，變頻控制方法有希望的未來使用長距離帶式輸送機(jī)驅(qū)動(dòng)器由于其優(yōu)良的性能。在三電平逆變器使用高