帶式輸送機(jī)及其牽引系統(tǒng)的外文翻譯、中英文翻譯、外文文獻(xiàn)翻譯

第 1 頁 外文原文： JOURNAL OF COAL SCIENCE&ENGINEERING (CHINA) ISSN 1006-9097 pp 83-87 Vo1.10 No.l June 200.1 Development of belt conveyor driving system FU Jun-qing(付峻青 )， WANG Cong(王聰 )， HUO Wei(霍偉 ) (Department of Information and Electrical Engineering, China University of Mining&Technology IBei,jing) Beijing 100083, China) Abstract A short review for the existing various driving methods for belt conveyor was given, which include the analysis and comparison about the advantages, disadvantages and suitable application range of these methods. Based on this the variable-frequency-control(VFC method for belt conveyor drive was fully discussed with focus on its application in medium-high voltage range. The principle of Neutral Point Clamped (NPC) Three 一 Level Inverter using high-voltage IGBTs together with the control strategy of rotor field-oriented vector control for induction motor drive were illustrated. Key words belt conveyor driving system, variable-frequency-control, three-level inverter Among the methods of material conveying employed， 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 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 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 An 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 important considerations in the drive systems 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 customerschoices1. 1 Analysis on conveyor drive technologies 1 1 Direct drives 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 fu11-voltage starters no control is provided for various conveyor loads and depending on the ratio between fu11- and no-1oad power requirements， empty 第 2 頁 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 1s 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 fu11-line voltage to the motor Motors with higher torque and pull up 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 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 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 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 systems particular specifications Wound rotor motors are appropriate for systems requiring more than 400 kW DC motor DC motors available from a fraction of thousands of kW ， are designed 第 3 頁 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 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 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,1oad 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 driven shafts The power produced by this coupling is based on the circulated fluids 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 l% 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,1ow-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 第 4 頁 principle as fixed-fill couplings The couplings 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 couplings 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 l00 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 l50 kW to 750 kW. 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, 第 5 頁 convert DC back to AC with frequency and voltage contro1 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 conveyor 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 improved 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 3kV 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 IGBTs Three-level voltage-fed inverters have recently become more and more popular for higher power drive applications because of their easy voltage sharing features 1ower dv/dt per switching for each of the devices， and superior harmonic quality at the output The availability of HV-IGBTs 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 6 kV Series connection of HV-IGBT modules is used in the 3 3 kV and 4 1 6 kV devices The 2 3 kV inverters need only one HV-IGBT per switch2,3. 2 1 Power section To meet the demands for medium voltage applications a three-level neutral 第 6 頁 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 O are the dc bus points The phase U， for example， is in state P(positive bus voltage)when the switches S1u and 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 O 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 O should be zero 2 2 Line side converter For standard applications a l2-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 Contro1 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 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 unit vector signals(cos and sin )are generated The vector rotator generates the voltage 第 7 頁 and angle 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， the three-level modulator uses two sets of reference waveforms Ur1 and Ur2 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-1ink 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 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 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 smal1 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 A1l 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 第 8 頁 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 IGBTs 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 NPC three 1evel 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-IGBTs together with the control strategy of rotor field-oriented vector control for induction motor drive is excellent for belt conveyor driving system References l Jim Ehler. Conveyor drive technologies offer smooth, soft startsJ. Motors& Drives, 2001(4): 28-35. 2 Sommer R, Mertens A. Medium voltage drive system with three-level NPC inverter using IGBTsA. IEE Colloquium on PWM Medium Voltage DrivesC. Birmingham,2000 3 Mertens A, Sommer R, Brunotte C. Applications of medium voltage drives with IGBT three-level inverterA. IEE colloquium on PWM medium voltage drivesC. Birmingham,2000 第 9 頁 中文譯文： 帶式輸送機(jī)及其牽引系統(tǒng) 在運(yùn)送大量的物料時，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)將會變得更大、更復(fù)雜，而驅(qū)動系統(tǒng)也已經(jīng)歷了一個演變過程，并將繼續(xù)這樣下去。如今，較大的輸送帶和多驅(qū)動系統(tǒng)需要更大的功率 ,比如 3 驅(qū)動系統(tǒng)需要給輸送帶750KW (成莊煤礦輸送機(jī)驅(qū)動系統(tǒng)的要求 )?？刂乞?qū)動力和加速度扭矩是輸送機(jī)的關(guān)鍵。一個高效的驅(qū)動系統(tǒng)應(yīng)該能順利的運(yùn)行 ,同時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)載分配在多個驅(qū)動上，扭矩和速度控制在驅(qū)動系統(tǒng)的設(shè)計中也是很重要的因素。由于輸送機(jī)驅(qū)動系統(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)動的驅(qū)動系統(tǒng)可供顧客選擇。 1 帶式輸送機(jī)驅(qū)動 1.1 帶式輸送機(jī)驅(qū)動方式 全電壓啟動 在全電壓啟動設(shè)計中 ， 帶式輸送機(jī)驅(qū)動軸通過齒輪傳動直接連接到電機(jī)。直接全壓驅(qū)動沒有為變化的傳送負(fù)載提供任何控制 ,根據(jù)滿載和空載功率需求的比率 ，空載啟動時比滿載可能快 3 4倍。此種方式的優(yōu)點(diǎn)是 :免維護(hù) ,啟動系統(tǒng)簡單 ， 低成本 ， 可靠性高。但是 ， 不能控制啟動扭矩和最大停止扭矩。因此 ， 這種方式只用于低功率 ,結(jié)構(gòu)簡單的傳送驅(qū)動中。 降壓啟動 隨著傳送驅(qū)動功率的增加 ,在加速期間控制使用的電機(jī)扭矩變 得越來越重要。由于電機(jī)扭矩是電壓的函數(shù) ,電機(jī)電壓必須得到控制 ， 一般用可控硅整流器 (SCR) 構(gòu)成的降壓啟動裝置 ， 先施加低電壓拉緊輸送帶 ,然后線性的增加供電電壓直到全電壓和最大帶速。但是 ， 這種啟動方式不會產(chǎn)生穩(wěn)定的加速度 ， 當(dāng)加速完成時 ,控制電機(jī)電壓的 SCR 鎖定在全導(dǎo)通 ， 為電機(jī)提供全壓。此種控制方式功率可達(dá)到 750kW。 繞線轉(zhuǎn)子感應(yīng)電機(jī) 繞線轉(zhuǎn)子感應(yīng)電機(jī)直接連接到驅(qū)動系統(tǒng)減速機(jī)上 ,通過在電機(jī)轉(zhuǎn)子繞組中串聯(lián)電阻控制電機(jī)轉(zhuǎn)矩。在傳送裝置啟動時 ,把電阻串聯(lián)進(jìn)轉(zhuǎn)子產(chǎn)生較低的轉(zhuǎn)矩 ， 當(dāng)傳送帶加速時 ， 電阻逐漸減少保 持穩(wěn)定增加轉(zhuǎn)矩。在多驅(qū)動系統(tǒng)中 ， 一個外加的滑差電阻可能將總是串聯(lián)在轉(zhuǎn)子繞組回路中以幫助均分負(fù)載。該方式的電機(jī)系統(tǒng)設(shè)計相對簡單 ， 但控制系統(tǒng)可能很復(fù)雜 ， 因?yàn)樗鼈兪腔谟嬎銠C(jī)控制的電阻切換。當(dāng)今 ， 控制系統(tǒng)的大多數(shù)是定制設(shè)計來滿足傳送系統(tǒng)的特殊規(guī)格。繞線轉(zhuǎn)子電機(jī)適合于需要 400kW以上的系統(tǒng)。 第 10 頁 直流 (DC)電機(jī) 大多數(shù)傳送驅(qū)動使用 DC 并勵電機(jī) ， 電機(jī)的電樞在外部連接?？刂艱C 驅(qū)動技術(shù)一般應(yīng)用 SCR裝置 ， 它允許連續(xù)的變速操作。 DC 驅(qū)動系統(tǒng)在機(jī)械上是簡單的 ,但設(shè)計的電子電路 ， 監(jiān)測和控制整個系統(tǒng) ， 相比于其他軟啟 動系統(tǒng)的選擇是昂貴的 ， 但在轉(zhuǎn)矩、負(fù)載均分和變速為主要考慮的場合 ,它又是一個可靠的 ， 節(jié)約成本的方式。 DC 電機(jī)一般使用在功率較大的輸送裝置上 ,包括需要輸送帶張力控制的多驅(qū)動系統(tǒng)和需要寬變速范圍的輸送裝置上。 1.2 液力偶合器 流體動力偶合器通常被稱為液力偶合器 ， 由三個基本單元組成 ： 充當(dāng)離心泵的葉輪 ,推進(jìn)水壓的渦輪和裝進(jìn)兩個動力部件的外殼。流體從葉輪到渦輪 ， 在從動軸產(chǎn)生扭矩。由于循環(huán)流體產(chǎn)生扭矩和速度 ， 在驅(qū)動軸和從動軸之間不需要任何機(jī)械連接。這種連接產(chǎn)生的動力決定于液力偶合器的充液量 ， 扭矩正比于輸入速度。因在 流體偶合中輸出速度小于輸入速度 ,其間的差值稱為滑差 ,一般為 1 % 3 %。傳遞功率可達(dá)幾千千瓦。 固定充液液力偶合器 固定充液液力偶合器是在結(jié)構(gòu)較簡單和僅具有有限的彎曲部分的輸送裝置中最常用的軟啟動裝置 ， 其結(jié)構(gòu)相對比較簡單 ， 成本又低 ， 對現(xiàn)在使用的大多數(shù)輸送機(jī)能提供優(yōu)良的軟啟動效果。 可變充液液力偶合器 也稱為限矩型液力偶合器。偶合器的葉輪裝在 AC 電機(jī)上 ,渦輪裝在從動減速器高速軸上 ， 包含操作部件的軸箱安裝在驅(qū)動基座。偶合器的旋轉(zhuǎn)外殼有溢出口 ,允許液體不斷地從工作腔中流出進(jìn)入一個分離的輔助腔 ， 油從 輔助腔通過一個熱交換器泵到控制偶合器充液量的電磁閥。為了控制單機(jī)傳動系統(tǒng)的啟動轉(zhuǎn)矩 ,必須監(jiān)測 AC 電機(jī)電流 ,給電磁閥的控制提供反饋?？勺兂湟阂毫ε己掀骺墒褂迷谥写蠊β瘦斔拖到y(tǒng)中 ，功率可達(dá)到數(shù)千千瓦。這種驅(qū)動無論在機(jī)械 ,或在電氣上都是很復(fù)雜的 ， 其驅(qū)動系統(tǒng)成本中等。 勺管控制液力偶合器 也稱為調(diào)速型液力偶合器。此種液力偶合器同樣由三個標(biāo)準(zhǔn)的液力偶合單元構(gòu)成 ， 即葉輪、渦輪和一個包含工作環(huán)路的外殼。此種液力偶合器需要在工作腔以外設(shè)置導(dǎo)管 (也稱勺管 ) 和導(dǎo)管腔 ， 依靠調(diào)節(jié)裝置改變勺管開度 (勺管頂端與旋轉(zhuǎn)外殼間距 ) 人為的改變工作腔的充液量 ,從而實(shí)現(xiàn)對輸出轉(zhuǎn)速的調(diào)節(jié)。這種控制提供了合理的平滑加速度 ， 但其計算機(jī)控制系統(tǒng)很復(fù)雜。勺管控制液力偶合器可以應(yīng)用在單機(jī)或多機(jī)驅(qū)動系統(tǒng) ， 功率范圍為 150kW 750kW。 1 3 變頻控制 (VFC) 變頻控制也是一種直接驅(qū)動方式 ， 它具有非常獨(dú)特的高性能。 VFC 裝置為感應(yīng)電機(jī)提供變化的頻率和電壓 ,產(chǎn)生優(yōu)良的啟動轉(zhuǎn)矩和加速度。 VFC設(shè)備是一個電力電子控制器 ,首先 第 11 頁 把 AC 整流成 DC ， 然后利用逆變器 ， 再將 DC 轉(zhuǎn)換成頻率、電壓可控的 AC。 VFC 驅(qū)動采用矢量控制或