【正文】 adays, 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 conveyors39。s design. Due to the advances in conveyor drive control technology, at present many more reliable. Costeffective and performance driven conveyor drive systems covering a wide range of power are available for customers39。 therefore. they are limited to the lowpower, simpleprofile conveyor belt drives. Reducedvoltage starters. As conveyor power requirements increase,controlling the applied motor torque during the acceleration period bees increasingly important. Because motor torque is a function of voltage, motor voltage must be controlled. This can be achieved through reducedvoltage starters by employing a silicon controlled rectifier (SCR). A mon starting method with SCR reducedvoltage 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 plete. the SCRs, which control the applied voltage to the electric motor. are locked in full conduction, providing fullline voltage to the motor. Motors with higher torque and pull vp torque, can provide better starting torque when bined 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 motor39。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 the maximum allowable revolutions per minute (r/min). with the majority of conveyor drives, a .DC shunt wound motor is used. Wherein the motor39。 the driven impeller, which acts as a centrifugal pump。s amount and density and the torque in proportion to input 10 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 used softstart 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 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 11 driving runner and a casing that encloses the working circuit. The casing is fitted with fixed o