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袋装面粉输送机的结构设计
袋装
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输送
结构设计
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河南理工大学万方科技学院本科生英文翻译_本科毕业设计（论文）中英文对照翻译 院（系部） 万方科技学院机械与动力工程系 专业名称 机械设计及其自动化 年级班级 机制08-2班 学生姓名 史 锐 指导老师 闫艳燕 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 customerchoices.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 controlVariable-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 1GBTsThree-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-link3 testing resultsAfter 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 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 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.带式输送机传动系统的发展富放射；王聪；霍巍（信息与电子工程系；中国矿业大学科技（北京）北京100083；中国） 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输送机驱动技术分析1.1直接驱动 一个完整的电压驱动设计，输送机机头轴直接耦合到电机通过齿轮传动。直接全压起动是足够的相对低功耗，直接全电压提供各种输送机负荷。根据不同的电台之间的充分和无负载功率的要求，早期开始的时间可以是三或四倍的速度比全负荷。该驱动凝视系统是双端弯曲，低成本和可靠的，但是，他们无法控制的起动转矩和最大扭矩：因此，他们是有限的输送皮带驱动。 降压起动器，如输送电力需求的增长，控制应用力矩电机在加速期间变得越来越重要。由于电动机的扭矩是一个函数的电压，电机电压控制。这可以通过降压起动器采用可控硅整流器。一个有效方法可控硅降压起动器适用低电压最初采取了输送带松弛。然后应用线性斜坡上定时全电压带加速度。当加速完成。可控硅控制，应用电压电动机。被锁在全传导，提供全系列电压的电动机。电机具有较高的转矩和最小转矩可以提供更好的起动转矩结合晶闸管，可满足尺寸水平的要求。 绕线转子感应电动机，绕线转子感应电动机直接连接到驱动系统减速器和修改标准交流感应电机。插入串联电阻与电机转子绕组的电机控制系统，控制电动机的转矩。用于输送机启动，抵抗是放置在与转子低初始转矩。为加速阻力降低，慢慢地保持恒定的扭矩。在多重驱动系统。外部滑动电阻也许在一系列与转子绕组在负载共享。电机系统有一个相对简单的设计。然而，控制系统可以更复杂，因为它们是基于计算机控制的电阻开关。今天，因为他们是根据计算机控制的电阻开关。今天，大多数控制系统是定制设计满足特定规格的输送系统。绕线式电机适合系统需要超过400千瓦。 直流电机，可从一个分数万千瓦，旨在提供以下恒转矩和恒功率速度高于额定转速到最大允许每分钟转数。与大多数输送机驱动器，直流复励电机。其中，马达旋转电枢连接外部。最常见的技术用于控制直流驱动器是一个可控硅整流装置。可连续变速运行。直流驱动系统是最简单的，但可以包括综合定制设计的电子监测和控制系统的完善。该系统的选择是昂贵的相对于其他软启动系统。但它是一个可靠的，高性价比的传动应用中，转矩，负载共享和变速是首要的考虑问题。直流电动机一般采用高次输送机，包括复杂的文件传送带多重驱动系统，增压系统的需要，皮带张力控制和输送需要一个广泛的变速范围。1.2磁流体耦合 磁流耦合，通常称为流体联轴器，是由三个基本要素构成；驱动系统，作为离心泵；驱动水轮机称为亚军和一个外壳包围的功率成分。磁流体液体从泵驱动叶轮驱动转轮，产生转矩和速度，无机械连接是需要的驱动和驱动轴。电力生产的这种耦合是基于循环液量和密度和扭矩比例输入转速。由于泵的作用在流体耦合取决于离心力。输出速度小于输入速度。称为滑移。这通常是1%和3%。基本液力联轴器可在配置从分数到几千瓦。 固定流体联轴器是最常用的软设备，简单带概况和有限的凸部分。他们是相对简单的，低成本，可靠，免维护设备，提供优良的软启动的结果，大多数带式输送机在使用今天。 多变联轴器与排空联轴器的工作原理是一样的联轴器。该类联轴器安装在交流电机和减速器高速轴上的驱动系统。房屋安装钛驱动包围基地工作电路。联轴器旋转外壳包含泄放口，不断使流体退出工作电路成为一个独立的液压油从水库通过热交换器，一个液压阀控制液体灌装去耦合。控制起动转矩的单一驱动输送系统交流电动机电流进行监测，提供反馈到控制的电磁阀。变填补排水联轴器用于介质高千瓦输送系统，可在尺寸上千千瓦。驱动器可以机械地复杂，在不同的控制参数。该系统可以电子驱动。驱动系统成本中高，这取决于所指定的
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