Thread Content
As conveying equipment is increasingly used in various industries, and as the structure of such equipment continues to evolve, the control systems for belt conveyors are also advancing. Below we will discuss the control systems for belt conveyors. In previous applications of belt conveyors, due to the high cost of frequency converters back then, liquid viscosity soft start devices were often used for the decentralized drive of long-distance horizontal belt conveyors at multiple points. The principle of the hydraulic viscosity control device is as follows: the coil current of the proportional valve in the hydraulic system → controls the oil pressure → determines the thickness of the oil film → results in a certain torque → which in turn relates to the motor power. The following analysis takes a horizontal three-point distributed drive as an example; in this type of drive, the multi-point drive system using a viscous soft-start device aims to achieve power balance regulation. The electrical control system of the belt conveyor uses one main drive motor, and a threshold value is set for the current difference. When the current difference between the motors other than the main motor and the main motor exceeds this threshold value, power adjustment is initiated: the control oil pressure of the hydraulic device with higher output power is reduced in order to increase the thickness of the oil film, and the same principle applies in reverse. Controlling the oil pressure is achieved by adjusting the electromagnetic proportional valve in the hydraulic system of the fluid viscosity control device. The advantages and disadvantages of using a hydraulic viscosity control system in belt conveyors are as follows: it enables adaptive adjustments to inherent differences such as the outer diameter of the drive drums at various points, the reduction ratio of the reducers, and the rated speed of the motors. In practical applications, liquid viscosity control systems still have many shortcomings. Issues such as slipping of the drive rollers other than the main motor, severe wear of the drive rollers, high starting shock, poor stability, and inability to operate at low speeds for extended periods exist. These problems not only increase the equipment’s failure rate but also **reduce the service life of the drive rollers and conveyor belts. We thought that the power balance in liquid viscosity control systems was only applicable to ideal long-spacing, multi-point distributed drive belt conveyors with uniform material flow, continuity, and simple terrain and operating conditions. Building on the experience gained through the continuous development of belt conveyors, and with the improvement in the cost-performance ratio of frequency converters in recent years, control systems that utilize these frequency converters have begun to be widely used in belt conveyors that require long-distance, multi-point distributed drive, thanks to their advantageous features. Conveyor belts equipped with frequency converters can achieve many advantageous functions such as slow starting, slow stopping, start-up with reduced damage under heavy loads, and low-speed belt testing. Inverters generally have speed control and torque control functions, and they can achieve accurate speed closed-loop control through encoder feedback. For multi-point, long-distance distributed drive applications that use frequency converters, speed master-slave control is employed: the drive at the front is designated as the master drive, with the speed setpoint being sent to it; the real-time speed from this master drive is then sent to the drives in the middle and at the back as speed setpoints, or alternatively, the real-time speed from the drive in the middle is sent to the drive at the back. During the initial debugging phase, if the rated speed of the motor, the reduction ratio of the reducer, the outer diameter of the drive drum, as well as the sequence and timing of startup are not set correctly, the conveyor belt will experience low tension and sagging in certain sections. Once the appropriate ratio is found, the aforementioned issues may still arise during the long-term operation of the equipment due to varying degrees of wear on the various drive rollers. As can be seen from the above, belt conveyors are constantly being upgraded in the course of development, and experience is accumulated through production processes. Our company will keep up with the trends of the times, take practical applications into account, and provide more comprehensive solutions to manufacture products that are better suited to the needs of our customers.