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1、本科毕业设计外文文献及译文文献、资料题目：Belt conveying systems and driving system文献、资料来源：期刊文献、资料发表（出版）日期：2012.3.2院 （部）： 机电工程学院专 业： 机械电子班 级： 姓 名： 学 号： 指导教师： 翻译日期： 2012.4.25外文文献：Belt conveying systems and driving system Among the methods of material conveying employed，belt conveyors play a very important part in the rel
2、iable 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 indiv
3、idual 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 sta
4、rts 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 pe
5、rformance-driven conveyor drive systems covering a wide range of power are available for customers choices。1 Analysis on conveyor drive technologies11 Direct drivesFull-voltage starters。With a full-voltage starter design，the conveyor head shaft is direct-coupled to the motor through the gear drive。D
6、irect 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 fast
7、er 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 drivesReduced-voltage starters。As conveyor power requirements in
8、crease，controlling the applied motor torque during the acceleration period becomes increasingly important。Because motor torque 1second 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 commo
9、n 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 complet
10、e，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 pullup torque，can provide better starting torque when combined with the SCR starters, which are available in sizes up to 750 KWWo
11、und 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 co
12、nveyor 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 loa
13、d 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 specificatio
14、ns。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 to deliver constant torque below base speed and constant kW above base speed to the maximum allowable revolutions per minute(r/min)，with the maj
15、ority 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 c
16、omplex 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 gene
17、rally 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。12 Hydrokinetic couplingHydrokinetic couplings，commonly referred to as fluid couplings，a
18、re 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 sh
19、aft。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 ac
20、tion 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
21、 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 toda
22、y。Variable-fill drain couplings。Drainable-fluid couplings work on the same 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 rotatin
23、g 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 t
24、orque 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 d
25、epending 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
26、 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 couplin
27、g，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。but the computer-based control system is very complex。Scoop control couplings are applied on conveyors requiring single or m
28、ultiple drives from 150 kW to 750 kW。2 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 easy voltage sharing features。lower dv/dt per switching for each of the d
29、evices，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 23 kV to 41 6 kV Series connection of HV-IGBT
30、 modules is used in the 33 kV and 41 6 kV devices。The 23 kV inverters need only one HV-IGBT per switch。21 Power sectionTo 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 of
31、fers 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
32、 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 dc bus points。The phase U，for example，is in state P(positive bus v
33、oltage)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
34、 point voltage balancing，the average current injected at O should be zero。22 Line side converterFor 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
35、 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。3 Testing resultsAfter Successful installation of three 750 kW /23 kV three-level inverter
36、s for one 27 km long belt conveyor driving system in Chengzhuang Mine。The performance of the whole VFC system was tested。Fig3 is taken from the test，which shows the excellent characteristic of the belt conveyor driving system with VFC controller。Fig3 includes four curves。The curve 1 shows the belt t
37、ension。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 sat
38、isfied characteristic for belt driving system。4 ConclusionsAdvances 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 s
39、hows 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 mediu
40、m 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 27 km long belt conveyor drives in Chengzhuang Mine indicates that the performance of NPC t
41、hree-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。中文译文：皮带传送系统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输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个演变过程，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,比如
42、3驱动系统需要给输送带750KW (成庄煤矿输送机驱动系统的要求)。控制驱动力和加速度扭矩是输送机的关键。一个高效的驱动系统应该能顺利的运行,同时保持输送带张紧力在指定的安全极限负荷内。为了负载分配在多个驱动上，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，空载启动时比满载可能快34倍。此种方式的优点是:免维
43、护,启动系统简单，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,结构简单的传送驱动中。降压启动 随着传送驱动功率的增加,在加速期间控制使用的电机扭矩变得越来越重要。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,然后线性的增加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，当加速完成时,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
44、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加转矩。在多驱动系统中，一个外加的滑差电阻可能将总是串联在转子绕组回路中以帮助均分负载。该方式的电机系统设计相对简单，但控制系统可能很复杂，因为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，它允许连续的变速操作。DC 驱动系统在机械上是简单的,但设计的电子电路，监测和控制整个系统，相比于其他软启动系
45、统的选择是昂贵的，但在转矩、负载均分和变速为主要考虑的场合,它又是一个可靠的，节约成本的方式。DC 电机一般使用在功率较大的输送装置上,包括需要输送带张力控制的多驱动系统和需要宽变速范围的输送装置上。1.2 液力偶合器流体动力偶合器通常被称为液力偶合器，由三个基本单元组成：充当离心泵的叶轮,推进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
46、定充液液力偶合器 固定充液液力偶合器是在结构较简单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，其结构相对比较简单，成本又低，对现在使用的大多数输送机能提供优良的软启动效果。可变充液液力偶合器 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，包含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,允许液体不断地从工作腔中流出进入一个分离的辅助腔，油从辅助腔通过一个热交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
47、驱动无论在机械,或在电气上都是很复杂的，其驱动系统成本中等。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标准的液力偶合单元构成，即叶轮、涡轮和一个包含工作环路的外壳。此种液力偶合器需要在工作腔以外设置导管(也称勺管) 和导管腔，依靠调节装置改变勺管开度(勺管顶端与旋转外壳间距) 人为的改变工作腔的充液量,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， 功率范围为150kW750kW。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
48、输出端出色的谐波品质，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) 的出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围。这种逆变器目前可以实现从2. 3kV到4. 16kV全范围的应用。HV-IGBT 模块串联可使用在3. 3kV和4. 16kV的设备。2. 3kV逆变器每个开关只需要一个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，开关频率可降低到原来的1/
49、 4，开关器件的电压额定值可减小到原来的1/ 2 ，附加到电机上的额外的瞬态电压应力也可能减少到原来的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 分别表示三相， 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 相处于状态P(正母线电压) ，反之，当开关S3U和S4U闭合时，U 相处于状态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该是零。2.2 输入端变流器为通常使用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要求，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级应用，可以用一个有源输入变流器取
