外文文献及翻译--带式输送机及其牵引系统(编辑修改稿)

外文文献及翻译--带式输送机及其牵引系统(编辑修改稿)内容摘要：

systems have a relatively simple a ,the control systems for these can be highly plex, because they are based on puter control of the resistance switching. Today, the majority of control systems are custom designed to meet a conveyor system39。 s particular 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 (r/min). with the majority of conveyor drives, a .DC shunt wound motor is used. Wherein the motor39。 s rotating armature is connected externally. The most mon technology for controlling DC drives is a SCR device. which allows for continual variablespeed operation. The DC drive system is mechanically simple, but can include plex customdesigned electronics to monitor and control the plete system. this system option is expensive in parison to othersoftstart systems. but it is a reliable, costeffective drive in applications in which torque,load sharing and variable speed are primary considerations. DC motors generally are used with higherpower conveyors, 10 including plex profile conveyors with multipledrive systems, booster tripper systems needing belt tension control and conveyors requiring a wide variablespeed range. 1. 2 Hydrokiic coupling Hydrokiic couplings, monly referred to as fluid couplings. are posed 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 ponents. 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 driver power produced by this coupling is based on the circulated fluid39。 s 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 1% and 3%. Basic hydrokiic couplings are available in configurations from fractional to several thousand KW. Fixedfill fluid couplings. Fixedfill fluid couplings are the most monly usedsoftstart devices for conveyors with simpler belt profiles and limited convex/concave sections. They are relatively simple,lowcost,reliable,maintenance free devices that provide excellent soft starting results to the majority of belt conveyors in use today. Variablefill drain couplings. Drainablefluid couplings work on the same principle as fixedfill couplings. The coupling39。 s 11 impellersare mounted on the AC motor and therunners on the driven reducer highspeed shaft. Housing mounted to the drive base encloses the working circuit. The coupling39。 s rotating casing contains bleedoff 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 solenoidoperated hydraulic valve that controls the filling of the fluid coupling. To control the starting torque of a singledrive 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 highkw conveyor systems and are available in sizes up to thousands of drives can be mechanically plex and depending on the control parameters. the system can be electronically intricate. The drive system cost is medium to high,depending upon size specified. Hydrokiic scoop control drive. The scoop control fluid coupling consists of the three 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 percent f。