機(jī)械專業(yè)外文翻譯(中英文翻譯)

1、外文翻譯英文原文Belt Conveying Systems Development of driving systemAmong the methods of material conveying employed， belt conveyorsplay a very important part inthe reliable carrying of material over longdistances at competitive costConveyor systems have become larger andmore complex and drive systems have

2、also been going through a process of evolution and will continue to do so Nowadays ，bigger belts require morepower 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)Th

3、e ability to control driveacceleration torque is critical to belt conveyors'performance An efficientdrive system should be able to provide smooth，soft starts while maintainingbelt tensions within the specified safe limitsFor load sharing on multipledrives torque and speed control are also import

4、ant considerations in the drive system 's design. Due to the advances in conveyor drive control technology ， at present many more reliableCost-effective andperformance-driven conveyor drive systems covering a wide range of power are available for customers 'choices 1.1 Analysis on conveyor d

5、rive technologies1 1 Direct drivesFull-voltage starters With a full-voltage starter design，the conveyor head shaft isdirect-coupled to the motor through the gear driveDirect full-voltage starters areadequate for relatively low-power, simple-profile conveyorsWith directfu11-voltage starters no contro

6、l is provided for various conveyor loads and depending on the ratio between fu11- and no-1oad power requirements，empty starting times can be three or four times faster than full loadThemaintenance-free starting system is simple， low-cost and very reliable However,they cannot control starting torque

7、and maximum stall torque；therefore they arelimited 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 funct

8、ion of voltage，motorvoltage must be controlledThis can be achieved through reduced-voltagestarters 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 li

9、near 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 theapplied voltage to the electric motor are locked in full conduction, providingfu11-line voltage to the motor Motors

10、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 KWWound rotor induction motorsWound rotor induction motors are connecteddirectly to the drive system reducer and are a modified configuration of a sta

11、ndard AC induction motorBy inserting resistance in series with the motor'srotor windings the modified motor control system controls motor torqueForconveyor starting ，resistance is placed in series with the rotor for low initial torque As the conveyor accelerates ，the resistance is reduced slowly

12、 to maintain a constant acceleration torqueOn multiple-drive systems an external slip resistormay be left in series with the rotor windings to aid in load sharing The motorsystems have a relatively simple designHowever, the control systems for thesecan be highly complex ， because they are based on c

13、omputer 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 400 kWDC motor DC motors available from a fraction of thousands of kW，a

14、redesigned to deliver constant torque below base speed and constant kW above base speed to the maximum allowable revolutions per minute(r/min) with themajority of conveyor drives, a DC shunt wound motor is usedWherein themotor 's rotating armature is connected externallyThe most common technolog

15、yfor controlling DC drives is a SCR device which allows for continualvariable-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 s

16、ystems but it is a reliable, cost-effective drive in applications in whichtorque,1oad sharing and variable speed are primary considerations DC motorsgenerally are used with higher-power conveyors， including complex profileconveyors with multiple-drive systems， booster tripper systems needing beltten

17、sion control and conveyors requiring a wide variable-speed range1 2 Hydrokinetic couplingHydrokinetic couplings ， commonly referred to as fluid couplingsarecomposed of three basic elements; the driven impeller, which acts as a centrifugal pump ；the driving hydraulic turbine known as the runner and a

18、 casing that encloses the two power components Hydraulic fluid is pumped from the drivenimpeller to the driving runner, producing torque at the driven shaft Becausecirculating hydraulic fluid produces the torque and speed，no mechanicalconnection is required between the driving and driven shafts The

19、powerproduced by this coupling is based on the circulated fluid's amount and densityand the torque in proportion to input speedBecause the pumping action withinthe fluid coupling depends on centrifugal forcesthe output speed is less than theinput speed Referred to as slip this normally is betwee

20、n l% and 3%Basichydrokinetic 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 rela

21、tively simple,1ow-cost,reliable,maintenance free devices that provide excellent soft starting results to the majority of belt conveyors in use todayVariable-fill drain couplingsDrainable-fluid couplings work on the sameprinciple as fixed-fill couplings The coupling 's impellers are mounted on th

22、e ACmotor and the runners on the driven reducer high-speed shaftHousing mountedto 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 rese

23、rvoir is pumped through aheat 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 drai

24、n couplings are used in medium to high-kW conveyor systems and are available in sizes up to thousands of kWThedrives can be mechanically complex and depending on the control parameters the system can be electronically intricateThe drive system cost ismedium to high, depending upon size specified Hyd

25、rokinetic scoop control driveThe scoop control fluid coupling consists ofthe three standard fluid coupling components： a driven impeller, a driving runnerand a casing that encloses the working circuitThe casing is fitted with fixedorifices that bleed a predetermined amount of fluid into a reservoir

26、When thescoop tube is fully extended into the reservoir, the coupling is l00 percent filled The scoop tube, extending outside the fluid coupling，is positioned using anelectric actuator to engage the tube from the fully retracted to the fully engaged position This control provides reasonably smooth a

27、cceleration ratesto but thecomputer-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 Theemphasizing dis

28、cussion 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 conv

29、eyor 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 contro1 VFC drives adopt vector control or direct torque control(DTC)technology ， and can a

30、dopt 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 curvesVFC drivesprovide excellent speed and torque control for starting conveyor belts and canalso be designed

31、to provide load sharing for multiple driveseasily VFC controllersare frequently installed on lower-powered conveyor drives，but when used at therange of medium-high voltage in the past the structure of VFC controllersbecomes very complicated due to the limitation of voltage rating of power semiconduc

32、tor 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 inseries Three-level voltage-fed PWM converter systems are recently showingincreasing pop

33、ularity 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 /23kV invertersha

34、s been successfully installed in ChengZhuang Mine for one 27-km long beltconveyor driving system in following the principle of three-level inverter will be discussed in detail 2 Neutral point clamped(NPC)three-level inverter using IGBTsThree-level voltage-fed inverters have recently become more and

35、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 superiorharmonic quality at the output The availability of HV-IGBTs has led to the designof a new range of medium-high voltage inverter using three-le

36、vel 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 33kV and 4 1 6 kV devices The 2 3 kV inverters need only one HV-IGBT per switch 2,3 .2 1 Power sectionTo meet the demands for medium volt

37、age applications a three-level neutralpoint clamped inverter realizes the power section In comparison to a two-levelinverter 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 1/4of the switching frequency

38、 is necessaryMoreover the voltage ratings of theswitches in NPC inverter topology will be reduced to 1/2and the additionaltransient 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

39、U Vand W denote each of the three phases respectively；P N and O are the dc buspoints The phase U ， for example ，is in state P(positive bus voltage)when the switches S 1u and S 2u are closed ， whereas it is in state N (negative bus voltage) when the switches S 3u and S 4u are closed At neutral point

40、clamping，the phaseis in O state when either S 2u or S 3u conducts depending on positive or negative phase current polarity ，respectively For neutral point voltage balancing，theaverage current injected at O should be zero 2 2 Line side converterFor standard applications a l2-pulse diode rectifier fee

41、ds the divided DC-link capacitor This topology introduces low harmonics on the line side For evenhigher 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 d

42、iode rectifier, using the same structure as the inverter2 3 Inverter controlMotor Contro1 Motor control of induction machines is realized by using a rotor flux oriented vector controller Fig2 shows the block diagram of indirect vector controlled drive that incorporates both constant torque and high

43、speed field-weakening regions wherethe PW M modulator was used .In this figure , the comma nd flux / is gen erated as function of speed. The feedback speed is added with the feed forward slipcomma nd sig nal . the result ing freque ncy sig nal is in tegrated and the n theunit vector sig nals(cos and

44、 sin )are gen erated . The vector rotator gen erates the voltage and an gle “ comma nds for the PW M as show nPWM Modulator . The dema nded voltage vector is gen erated using an elaborate PWM modulator . The modulator extends the concepts of space-vector modulation to the three-level inverter. The o

45、peration can be explained by startingfrom a regularly sampled sin e-tria ngle comparis on from two-level inv erter . In stead of using one set of refere nee waveforms and one tria ngle defi ning the switchi ng freque ncy, the three-level modulator uses two sets ofreferenee waveforms U ri and U r2 an

46、d just one triangle . Thus, each switching tran siti on is used in an optimal way so that several objectives are reached at the same time .Very low harm onics are gen erated . The switch ing freque ncy is low and thus switch ing losses are mini mized. As in a two-level inv erter, a zero-seque neecom

47、p onent can be added to each set of refere nee waveform s in order to maximize the fun dame ntal voltage comp onent. As an additi onal degree offreedom , the position of the referenee waveform s within the triangle can be changed . This can be used for current balanee in the two halves of the DC-lin

48、k 3 Testi ng resultsAfter Successful in stallation of three 750 kW /2. 3 kV three-level in verters forone 2 . 7 km long belt eonveyor driving system in Chengzhuang Mine. Theperformance of the whole VFC system was testedFig3 is taken from the test ，which shows the excellent characteristic of the belt

49、 conveyor driving system with VFC controller Fig3 includes four curves The curve 1 shows the belt tensionFrom the curveit can be find that the fluctuation range of the belt tension is very smal1 Curve 2and curve 3 indicate current and torque separately Curve 4 shows the velocity ofthe controlled bel

50、t The belt velocity have the “ s”shape characteristic A1l the results of the test show a very satisfied characteristic for belt driving system4 ConclusionsAdvances in conveyor drive control technology in recent years have resulted in many more reliable Cost-effective and performance-driven conveyor

51、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 performancesThe NPC three-level inverter using highvoltage IGBTs make the Variable frequency control in medium

52、 voltage applications become much more simple because the inverter itself can provide the medium voltage needed at the motor terminals， thus eliminating the step-uptransformer in most applications in the pastThe testing results taken from the VFC control system with NPC three1evelinverters used in a

53、 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(shí)，帶

54、式輸送機(jī)在長(zhǎng)距離的運(yùn)輸中起到了非常重要的競(jìng)爭(zhēng)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 )。控制驅(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。1 帶式輸送機(jī)驅(qū)動(dòng)1.1 帶式輸送機(jī)驅(qū)

55、動(dòng)方式全電壓?jiǎn)?dòng) 在全電壓?jiǎn)?dòng)設(shè)計(jì)中，帶式輸送機(jī)驅(qū)動(dòng)軸通過齒輪傳動(dòng)直接連接到電 機(jī)。直接全壓驅(qū)動(dòng)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(dòng)時(shí)比滿載可能快34倍。此種方式的優(yōu)點(diǎn)是：免維護(hù)，啟動(dòng)系統(tǒng)簡(jiǎn)單，低成本，可 靠性高。但是，不能控制啟動(dòng)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(jiǎn)單的傳送驅(qū)動(dòng)中。降壓?jiǎn)?dòng) 隨著傳送驅(qū)動(dòng)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?jiǎn)?dòng)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

56、速。但是，這種啟動(dòng)方式不會(huì)產(chǎn)生穩(wěn)定的加速度， 當(dāng)加速完成時(shí) ,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(dòng)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(dòng)時(shí) ,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(shí)，電阻逐漸減少保持穩(wěn)定增加轉(zhuǎn)矩。在多驅(qū)動(dòng)系統(tǒng)中，一個(gè)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(jì)相對(duì)簡(jiǎn) 單，但控制系統(tǒng)可能很復(fù)雜，因?yàn)樗鼈兪腔谟?jì)算機(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(jì)來滿足傳送系統(tǒng)的特殊規(guī)格。 繞線轉(zhuǎn)

57、子電機(jī)適合于需要 400kW 以上的系 統(tǒng)。直流(DC)電機(jī)大多數(shù)傳送驅(qū)動(dòng)使用DC并勵(lì)電機(jī)，電機(jī)的電樞在外部連接?？刂艱C驅(qū)動(dòng)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(dòng)系統(tǒng)在機(jī)械上是簡(jiǎn)單 的,但設(shè)計(jì)的電子電路，監(jiān)測(cè)和控制整個(gè)系統(tǒng)，相比于其他軟啟動(dòng)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(chǎng)合 ,它又是一個(gè)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(dòng)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(dòng)力偶合器通常被稱為液力偶合器，由三個(gè)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(gè)動(dòng)力部件

58、的外殼。流體從葉輪到渦輪，在從動(dòng)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(dòng)軸和從動(dòng)軸之間不需要任何機(jī)械連接。這種連接產(chǎn)生 的動(dòng)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(jiǎn)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(dòng)裝置，其結(jié)構(gòu)相對(duì)比較簡(jiǎn)單，成本又低，對(duì)現(xiàn)在使用的 大多數(shù)輸送機(jī)能提供優(yōu)良的軟啟動(dòng)效果?？勺兂湟阂毫ε己掀?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(dòng)減速器高速軸上，包含操作部件的軸箱安裝在驅(qū)動(dòng)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(gè)分離的輔助腔，