机械专业外文翻译中英文翻译

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1、外文翻译英文原文Belt Conveying Systems Development of driving system 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 costConveyor systems have become larger and more complex and drive systems h

2、ave also been going through a process of evolution and will continue to do soNowadays，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

3、)The ability to control drive acceleration torque is critical to belt conveyors performanceAn efficient drive system should be able to provide smooth，soft starts while maintaining belt tensions within the specified safe limitsFor load sharing on multiple drivestorque and speed control are also impor

4、tant considerations in the drive systems design. Due to the advances in conveyor drive control technology，at present many more reliableCost-effective and performance-driven conveyor drive systems covering a wide range of power are available for customers choices1.1 Analysis on conveyor drive technol

5、ogies11 Direct drivesFull-voltage startersWith a full-voltage starter design，the conveyor head shaft is direct-coupled to the motor through the gear driveDirect full-voltage starters are adequate for relatively low-power, simple-profile conveyorsWith direct fu11-voltage startersno control is provide

6、d for various conveyor loads anddepending on the ratio between fu11- and no-1oad power requirements，empty starting times can be three or four times faster than full loadThe maintenance-free starting system is simple，low-cost and very reliableHowever, they cannot control starting torque and maximum s

7、tall torque；thereforethey are limited to the low-power, simple-profile conveyor belt drivesReduced-voltage startersAs conveyor power requirements increase，controlling the applied motor torque during the acceleration period becomes increasingly importantBecause motor torque 1s a function of voltage，m

8、otor voltage must be controlledThis 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 slackand then to apply a timed linear ramp up to

9、full voltage and belt speedHowever, this starting method will not produce constant conveyor belt accelerationWhen acceleration is completethe SCRs, which control the applied voltage to the electric motor are locked in full conduction, providing fu11-line voltage to the motorMotors with higher torque

10、 and pullup 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 connected directly to the drive system reducer and are a modified configuration of a standard AC induction

11、motorBy inserting resistance in series with the motors rotor windingsthe modified motor control system controls motor torqueFor conveyor starting，resistance is placed in series with the rotor for low initial torqueAs the conveyor accelerates，the resistance is reduced slowly to maintain a constant ac

12、celeration torqueOn multiple-drive systemsan external slip resistor may be left in series with the rotor windings to aid in load sharingThe motor systems have a relatively simple designHowever, the control systems for these can be highly complex，because they are based on computer control of the resi

13、stance switchingToday，the majority of control systems are custom designed to meet a conveyor systems particular specificationsWound rotor motors are appropriate for systems requiring more than 400 kW DC motorDC motorsavailable from a fraction of thousands of kW ，are designed to deliver constant torq

14、ue 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 usedWherein the motors rotating armature is connected externallyThe most common technology for controlling DC drives is a SCR dev

15、ice which allows for continual variable-speed operationThe DC drive system is mechanically simple, but can include complex custom-designed electronics to monitor and control the complete systemThis system option is expensive in comparison to other soft-start systemsbut it is a reliable, cost-effecti

16、ve drive in applications in which torque,1oad sharing and variable speed are primary considerationsDC 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 w

17、ide variable-speed range12 Hydrokinetic couplingHydrokinetic couplings，commonly referred to as fluid couplingsare 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 compone

18、ntsHydraulic fluid is pumped from the driven impeller to the driving runner, producing torque at the driven shaftBecause circulating hydraulic fluid produces the torque and speed，no mechanical connection is required between the driving and driven shaftsThe power produced by this coupling is based on

19、 the circulated fluids amount and density and the torque in proportion to input speedBecause the pumping action within the fluid coupling depends on centrifugal forcesthe output speed is less than the input speedReferred to as slipthis normally is between l% and 3%Basic hydrokinetic couplings are av

20、ailable in configurations from fractional to several thousand kW Fixed-fill fluid couplingsFixed-fill fluid couplings are the most commonly used soft-start devices for conveyors with simpler belt profiles and limited convex/concave sectionsThey are relatively simple,1ow-cost,reliable,maintenance fre

21、e devices that provide excellent soft starting results to the majority of belt conveyors in use todayVariable-fill drain couplingsDrainable-fluid couplings work on the same principle as fixed-fill couplingsThe couplings impellers are mounted on the AC motor and the runners on the driven reducer high

22、-speed shaftHousing mounted to the drive base encloses the working circuitThe couplings rotating casing contains bleed-off orifices that continually allow fluid to exit the working circuit into a separate hydraulic reservoirOil from the reservoir is pumped through a heat exchanger to a solenoid-oper

23、ated hydraulic valve that controls the filling of the fluid couplingTo control the starting torque of a single-drive conveyor system，the AC motor current must be monitored to provide feedback to the solenoid control valveVariable fill drain couplings are used in medium to high-kW conveyor systems an

24、d are available in sizes up to thousands of kW The drives can be mechanically complex and depending on the control parametersthe system can be electronically intricateThe drive system cost is medium to high, depending upon size specifiedHydrokinetic scoop control driveThe scoop control fluid couplin

25、g consists of the three standard fluid coupling components：a driven impeller, a driving runner and a casing that encloses the working circuitThe casing is fitted with fixed orifices that bleed a predetermined amount of fluid into a reservoirWhen the scoop tube is fully extended into the reservoir, t

26、he coupling is l00 percent filledThe 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 positionThis control provides reasonably smooth acceleration ratesto but the computer-based control system i

27、s very complexScoop control couplings are applied on conveyors requiring single or multiple drives from l50 kW to 750 kW.13 Variable-frequency control(VFC)Variable frequency control is also one of the direct drive methodsThe emphasizing discussion about it here is because that it has so unique chara

28、cteristic 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 drivesVFC drivesavailable from fractional to several th

29、ousand(kW ), are electronic controllers that rectify AC line power to DC and，through an inverter, convert DC back to AC with frequency and voltage contro1VFC drives adopt vector control or direct torque control(DTC)technology，and can adopt different operating speeds according to different loadsVFC d

30、rives can make starting or stalling according to any given S-curvesrealizing the automatic track for starting or stalling curvesVFC drives provide excellent speed and torque control for starting conveyor beltsand can also be designed to provide load sharing for multiple driveseasily VFC controllers

31、are frequently installed on lower-powered conveyor drives，but when used at the range of medium-high voltage in the pastthe 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 va

32、riable speed is often solved with low-voltage inverters using step-up transformer at the output，or with multiple low-voltage inverters connected in seriesThree-level voltage-fed PWM converter systems are recently showing increasing popularity for multi-megawatt industrial drive applications because

33、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 devicesThis kind of VFC system with three 750 kW /23kV inverters has been successfully installed in ChengZhuang Mine for one 27-km l

34、ong belt conveyor driving system in following the principle of three-level inverter will be discussed in detail2 Neutral point clamped(NPC)three-level inverter using IGBTsThree-level voltage-fed inverters have recently become more and more popular for higher power drive applications because of their

35、 easy voltage sharing features1ower dv/dt per switching for each of the devices，and superior harmonic quality at the outputThe availability of HV-IGBTs has led to the design of a new range of medium-high voltage inverter using three-level NPC topologyThis kind of inverter can realize a whole range w

36、ith a voltage rating from 23 kV to 41 6 kV Series connection of HV-IGBT modules is used in the 33 kV and 41 6 kV devicesThe 23 kV inverters need only one HV-IGBT per switch2,3.21 Power sectionTo meet the demands for medium voltage applicationsa three-level neutral point clamped inverter realizes the

37、 power sectionIn comparison to a two-level inverterthe 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 necessaryMoreover the voltage ratings of the switches in NPC inverter

38、 topology will be reduced to 1/2and 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 1UV and W denote each of the three phases respectively；P N and O are the

39、 dc bus pointsThe 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 closedAt neutral point clamping，the phase is in O state when either S2u or S3u conducts depending on pos

40、itive or negative phase current polarity，respectivelyFor neutral point voltage balancing，the average current injected at O should be zero22 Line side converterFor standard applicationsa l2-pulse diode rectifier feeds the divided DC-link capacitorThis topology introduces low harmonics on the line sid

41、eFor even higher requirements a 24-pulse diode rectifier can be used as an input converterFor more advanced applications where regeneration capability is necessary, an active frontend converter can replace the diode rectifier, using the same structure as the inverter23 Inverter controlMotor Contro1M

42、otor control of induction machines is realized by using a rotor fluxoriented vector controllerFig2 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 usedIn this figure，the command flu

43、x is generated as function of speedThe 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 generatedThe vector rotator generates the voltage and angle commands for the PW M as shownPWM Modu

44、latorThe demanded voltage vector is generated using an elaborate PWM modulatorThe modulator extends the concepts of space-vector modulation to the three-level inverterThe operation can be explained by starting from a regularly sampled sine-triangle comparison from two-level inverterInstead of using

45、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 triangleThus, each switching transition is used in an optimal way so that several objectives are reached at the same time Very low

46、 harmonics are generatedThe switching frequency is low and thus switching losses are minimizedAs 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 componentAs an additional degree of freedom，the position o

47、f the reference waveform s within the triangle can be changedThis can be used for current balance in the two halves of the DC-1ink3 Testing resultsAfter Successful installation of three 750 kW /23 kV three-level inverters for one 27 km long belt conveyor driving system in Chengzhuang MineThe perform

48、ance of the whole VFC system was testedFig3 is taken from the test，which shows the excellent characteristic of the belt conveyor driving system with VFC controllerFig3 includes four curvesThe curve 1 shows the belt tensionFrom the curve it can be find that the fluctuation range of the belt tension i

49、s very smal1Curve 2 and curve 3 indicate current and torque separatelyCurve 4 shows the velocity of the controlled beltThe belt velocity have the“s”shape characteristicA1l the results of the test show a very satisfied characteristic for belt driving system4 ConclusionsAdvances in conveyor drive cont

50、rol technology in recent years have resulted in many more reliableCost-effective and performance-driven conveyor drive system choices for usersAmong these choices，the Variable frequency control (VFC) method shows promising use in the future for long distance belt conveyor drives due to its excellent

51、 performancesThe 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 appl

52、ications in the pastThe testing results taken from the VFC control system with NPC three1evel inverters used in a 27 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 v

53、ector control for induction motor drive is excellent for belt conveyor driving system中文译文：带式输送机及其牵引系统 在运送大量的物料时，带式输送机在长距离的运送中起到了非常重要的竞争作用。输送系统将会变得更大、更复杂，而驱动系统也已经历了一种演变过程，并将继续这样下去。如今，较大的输送带和多驱动系统需要更大的功率,例如3驱动系统需要给输送带750KW (成庄煤矿输送机驱动系统的规定)。控制驱动力和加速度扭矩是输送机的核心。一种高效的驱动系统应当能顺利的运营,同步保持输送带张紧力在指定的安全极限负荷内。为了负

54、载分派在多种驱动上，扭矩和速度控制在驱动系统的设计中也是很重要的因素。由于输送机驱动系统控制技术的进步,目前更多可靠的低成本和高效驱动的驱动系统可供顾客选择1。1 带式输送机驱动1.1 带式输送机驱动方式全电压启动 在全电压启动设计中，带式输送机驱动轴通过齿轮传动直接连接到电机。直接全压驱动没有为变化的传送负载提供任何控制,根据满载和空载功率需求的比率，空载启动时比满载也许快34倍。此种方式的长处是:免维护,启动系统简朴，低成本，可靠性高。但是，不能控制启动扭矩和最大停止扭矩。因此，这种方式只用于低功率,构造简朴的传送驱动中。降压启动 随着传送驱动功率的增长,在加速期间控制使用的电机扭矩变得越

55、来越重要。由于电机扭矩是电压的函数,电机电压必须得到控制，一般用可控硅整流器(SCR) 构成的降压启动装置，先施加低电压拉紧输送带,然后线性的增长供电电压直到全电压和最大带速。但是，这种启动方式不会产生稳定的加速度，当加速完毕时,控制电机电压的SCR 锁定在全导通，为电机提供全压。此种控制方式功率可达到750kW。绕线转子感应电机 绕线转子感应电机直接连接到驱动系统减速机上,通过在电机转子绕组中串联电阻控制电机转矩。在传送装置启动时,把电阻串联进转子产生较低的转矩，当传送带加速时，电阻逐渐减少保持稳定增长转矩。在多驱动系统中，一种外加的滑差电阻也许将总是串联在转子绕组回路中以协助均分负载。该方

56、式的电机系统设计相对简朴，但控制系统也许很复杂，由于它们是基于计算机控制的电阻切换。当今，控制系统的大多数是定制设计来满足传送系统的特殊规格。绕线转子电机适合于需要400kW以上的系统。直流(DC)电机 大多数传送驱动使用DC 并励电机，电机的电枢在外部连接。控制DC 驱动技术一般应用SCR装置，它容许持续的变速操作。DC 驱动系统在机械上是简朴的,但设计的电子电路，监测和控制整个系统，相比于其她软启动系统的选择是昂贵的，但在转矩、负载均分和变速为重要考虑的场合,它又是一种可靠的，节省成本的方式。DC 电机一般使用在功率较大的输送装置上,涉及需要输送带张力控制的多驱动系统和需要宽变速范畴的输送

57、装置上。1.2 液力偶合器流体动力偶合器一般被称为液力偶合器，由三个基本单元构成：充当离心泵的叶轮,推动水压的涡轮和装进两个动力部件的外壳。流体从叶轮到涡轮，在从动轴产生扭矩。由于循环流体产生扭矩和速度，在驱动轴和从动轴之间不需要任何机械连接。这种连接产生的动力决定于液力偶合器的充液量，扭矩正比于输入速度。因在流体偶合中输出速度不不小于输入速度,其间的差值称为滑差,一般为1 %3 %。传递功率可达几千千瓦。固定充液液力偶合器 固定充液液力偶合器是在构造较简朴和仅具有有限的弯曲部分的输送装置中最常用的软启动装置，其构造相对比较简朴，成本又低，对目前使用的大多数输送机能提供优良的软启动效果。可变充

58、液液力偶合器 也称为限矩型液力偶合器。偶合器的叶轮装在AC 电机上,涡轮装在从动减速器高速轴上，涉及操作部件的轴箱安装在驱动基座。偶合器的旋转外壳有溢出口,容许液体不断地从工作腔中流出进入一种分离的辅助腔，油从辅助腔通过一种热互换器泵到控制偶合器充液量的电磁阀。为了控制单机传动系统的启动转矩,必须监测AC 电机电流,给电磁阀的控制提供反馈。可变充液液力偶合器可使用在中大功率输送系统中，功率可达到数千千瓦。这种驱动无论在机械,或在电气上都是很复杂的，其驱动系统成本中档。勺管控制液力偶合器 也称为调速型液力偶合器。此种液力偶合器同样由三个原则的液力偶合单元构成，即叶轮、涡轮和一种涉及工作环路的外壳

59、。此种液力偶合器需要在工作腔以外设立导管(也称勺管) 和导管腔，依托调节装置变化勺管开度(勺管顶端与旋转外壳间距) 人为的变化工作腔的充液量,从而实现对输出转速的调节。这种控制提供了合理的平滑加速度，但其计算机控制系统很复杂。勺管控制液力偶合器可以应用在单机或多机驱动系统， 功率范畴为150kW750kW。13 变频控制(VFC)变频控制也是一种直接驱动方式，它具有非常独特的高性能。VFC 装置为感应电机提供变化的频率和电压,产生优良的启动转矩和加速度。VFC设备是一种电力电子控制器,一方面把AC 整流成DC ，然后运用逆变器，再将DC 转换成频率、电压可控的AC。VFC 驱动采用矢量控制或直

60、接转矩控制(DTC) 技术，能根据不同的负载采用不同的运营速度。VFC 驱动能根据给定的S 曲线启动或停车，实现自动跟踪启动或停车曲线。VFC 驱动为传送带启动提供了优良的速度和转矩控制，也能为多机驱动系统提供负载均分。VFC 控制器可以容易地装在小功率输送机驱动上。过去在中高电压使用时，VFC 设备的构造由于受电力半导体器件的电压额定值限制而变得很复杂，中高电压的变速传动常常使用低压逆变器，然后在输出端使用升压变压器，或使用多种低压逆变器串联来解决。与简朴的器件串联连接的两电平逆变器系统比较，由于串联器件之间容易均压以及输出端可以有更好的谐波特性，三电平电压型PWM 逆变器系统在数兆瓦工业传

61、动中近年来获得了越来越多的应用。由三台750kW/ 2. 3kV 的这种逆变器构成的VFC 系统已经成功安装在成庄煤矿长2. 7km的带式输送机驱动系统中。2 使用IGBT的中性点箝位三电平逆变器由于串联器件电压均分容易,器件每次开关的d v/ d t 低以及输出端杰出的谐波品质，三电平电压型逆变器在大功率传动应用中变得越来越流行。高压IGBT(HV-IGBT) 的浮现使得应用三电平中性点箝位原理的中高压逆变器设计有了更大的应用范畴。这种逆变器目前可以实现从2. 3kV到4. 16kV全范畴的应用。HV-IGBT 模块串联可使用在3. 3kV和4. 16kV的设备。2. 3kV逆变器每个开关只

62、需要一种HV-IGBT2,3。21 主功率逆变电路主功率逆变电路用三电平中点箝位电压型逆变器实现,可以满足中高压交流传动应用的需要。与两电平电压型逆变器相比，三电平中点箝位电压型逆变器提供三个电压级别给输出端，对于同样的输出电流品质，开关频率可减少到本来的1/ 4，开关器件的电压额定值可减小到本来的1/ 2 ，附加到电机上的额外的瞬态电压应力也也许减少到本来的1/ 2 。三电平中点箝位电压型逆变器的开关状态可归纳于表1 ，U ，V 和W 分别表达三相， P，N 和O 是直流母线上的三个点。例如，当开关S1U和S2U闭合时，U 相处在状态P(正母线电压) ，反之，当开关S3U和S4U闭合时，U

63、相处在状态N (负母线电压) 。在中性点箝位时,该相在O 状态，这时根据相电流极性的正负,或者是S2U导通或者是S3U导通。为了保证中性点电压平衡，在O 点被注入的平均电流应当是零。2.2 输入端变流器为一般使用12 脉冲二极管整流器给直流环节电容器充电,在输入端引入的谐波是很小的。若对输入谐波有更高的规定，可以使用24 脉冲二极管整流器作为输入变流器。对于需要有再生能力的更高档应用，可以用一种有源输入变流器取代二极管整流器，这时输入整流器与输出逆变器为同一构造。2.3 逆变器控制电机控制 感应电机的控制可以使用转子磁场定向矢量控制器实现,通过使用PWM 调制器完毕了恒转矩区和高速弱磁区的控制

64、。图2 为间接矢量控制框图。图中指令磁通r 是速度的函数,反馈速度和前馈滑差控制信号sl相加。对相加成果的频率信号积分，然后产生单位矢量(cose 和sine ) ，最后通过矢量旋转器产生电压角控制PWM 调制器。PWM调制器 该调制器事实上是把空间矢量调制概念扩展到三电平逆变器。其基本原理是三电平PWM 调制器使用两个参照波Ur1 和Ur2，但只使用一种三角波。它以一种优化方式拟定每一次开关时刻。产生的谐波尽量的小，使用尽量低的开关频率以最小化开关损耗；可将零序成分加到每一种参照波里以便最大化基波电压。作为一种附加的自由度,参照波与三角波的相对位置可变化，这可以用于直流环节中点的电流平衡。3

65、 测试成果三个750kW/ 2. 3kV 三电平逆变器在成庄煤矿2. 7km 长带式输送机驱动系统成功安装之后,对整个变频传动系统(VFC) 的性能进行了测试,测试成果显示出使用VFC 控制系统的带式输送机的优良特性。图3为测试成果波形。由图看出,曲线1 显示受控带速,带速呈S 形曲线形状,曲线2 、3 分别表达电流和扭矩,曲线4 显示带张力。从图中可以发现,带张力的波动范畴很小，所有检测成果显示出带式输送机驱动系统令人满意的特性。4 结论近年来输送机驱动控制技术的进步已更为可靠，符合低成本效益和高效驱动的驱动系统为顾客提供了选择。在这些选择中，可变频率控制(VFC)的措施显现出在将来长距离输送中带式输送机扮演了重要的角色。使用高压IGBT 的中点嵌位三电平逆变器自身可以提供电机终端所需的供电中高压,使变频控制的应用更为简朴。通过成庄煤矿2. 7km