带式输送机及其牵引系统机械外文文献翻译中英文翻译外文翻译.docx

1、带式输送机及其牵引系统机械外文文献翻译中英文翻译外文翻译 JINGGANGSHAN UNIVERSITY外文翻译题 目 调整送料量输送装置设计学 院 机电工程学院 专 业 机械制造及其自动化 班 级 机制11本（1）班 学 号 110611014 姓 名 蓝善龙 指导教师 康志成教授 起讫时间 2014.12.12015.4 教 务 处 印 制AbstractBulkmaterialtransportationrequirementshavecontinuedtopressthebeltconveyorindustrytocarryhighertonnagesoverlongerdistanc

2、esandmorediverseroutes.Inorderkeepup,significanttechnologyadvanceshavebeenrequiredinthefieldofsystemdesign,analysisandnumericalsimulation.Theapplicationoftraditionalcomponentsinnon-traditionalapplicationsrequiringhorizontalcurvesandintermediatedriveshavechangedandexpandedbeltconveyorpossibilities.Ex

3、amplesofcomplexconveyingapplicationsalongwiththenumericaltoolsrequiredtoinsurereliabilityandavailabilitywillbereviewed.Belt Conveying Systems Development of driving systemAmong the methods of material conveying emploved, belt conveyors play a very imporient part in the reliable carrying of material

4、over long distances at competitive cost. Conveyor systems have become larger and more complex and drive systems have a l so 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 a

5、s 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. A efficient drive system should be able to provide smooth, soft starts while maintainin

6、g belt tensions within the specified safe limits. For load sharing on multiple drives. torque and speed control are also 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 conveyo

7、r drive systems covering a wide range of power are available for customers choices1. 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 8 full-vo

8、ltage 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 our times faster than f

9、ull 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 inc

10、rease,controlling theapplied 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 (SCR). A common

11、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 comple

12、te. 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 pull -vp torque, can providebetterstarting torque when combined with the SCR starters, which are available in sizesup to 750 K

13、W. Wound rotor induction motors. Wound rotor induction motors are 9 connected directly to the drive system reducer and are a modified onfiguration of a standard AC induction motor. By inserting resistance in series with the motors rotor windings. the modified motor control System controls motor torq

14、ue. 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

15、 to aid in load sharing .the motor systems have a relatively simple a 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 part

16、icular specifications. Wound rotor motors are appropriate for systems requiring more than 400KW. 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 themaximum allowable revolutions per minute

17、(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

18、 simple, but can include complex custom-designed electronics to monitor and control the complete system. this system option is expensive in comparison to othersoft-start systems. but it is a reliable, cost-effective drive in applications in which torque,load sharing and variable speed are primary co

19、nsiderations. DC motors generally are used with higher-power conveyors, 10 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 2. Hydrokinetic couplings, c

20、ommonly 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 drivin

21、g 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 driver shafts.The power produced by this coupling is based on the circulated fluids amount and density and the torque in pro

22、portion 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 1% and 3%. Basic hydrokinetic couplings are available in configurations from fractional to several

23、thousand KW. Fixed-fill fluid couplings. Fixed-fill fluid couplings are the most commonly usedsoft-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 re

24、sults to the majority of belt conveyors in use today. Variable-fill drain couplings. Drainable-fluid couplings work on the same principle as fixed-fill couplings. The couplings 11 impellersare mounted on the AC motor and therunners on the driven reducer high-speed shaft. Housing mounted to the drive

25、 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 t

26、he 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

27、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

28、standard fluid coupling cmponents: 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 100 p

29、ercent 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 comple

30、x. Scoop control couplings are 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. V

31、FC 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

32、an inverter, convert DC back to AC with frequency and voltage control. VFC drives adopt vector control or direct torquecontrol(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 inst