带式输送机及其牵引系统的外文翻译、中英文翻译、外文文献翻译

第 1 页 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(王聪 )， HUO Wei(霍伟 ) (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 页 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 页 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 页 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 页 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 页 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 页 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 页 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 页 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 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 3 4倍。此种方式的优点是 :免维护 ,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。 第 10 页 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 150kW 750kW。 1 3 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设备是一个电力电子控制器 ,首先 第 11 页 把 AC 整流成 DC ， 然后利用逆变器 ， 再将 DC 转换成频率、电压可控的 AC。 VFC 驱动采用矢量控制或