With the improvement of coal mining equipment and coal mining technology and the continuous increase of raw coal output, the conveyor belt conveyor system plays a key role in coal mine production. Whether the control system of the belt conveyor is superior and reliable, in a sense, determines the production capacity and the degree of automation of a coal mine. The project site is located in the Gold Ocean Industrial Park of China Coal Gold Group in Beizhouzhuang Town, Shanyin County, Shuozhou City, northwestern Shanxi. The project site is shown below:

The project adopts NA400 series programmable controller as the core. On the one hand, the host computer platform communicates with PLC via Ethernet, receives the operator's control commands, and completes the start and stop of the belt conveyor equipment and the adjustment of process parameters. On the other hand, through Ethernet, various parameters of the belt running process can be transmitted to the centralized control center, so that the whole mine can uniformly arrange human resources and material resources to achieve safe and efficient production.

System configuration and description

The project takes the belt conveyor of the coal mine as the control object and is based on the monitoring system design of NA400PLC and Kingview software.

The belt conveyor frequency conversion control system is mainly divided into five parts: PLC control part, frequency conversion drive part, automatic tension part, belt conveyor protection part, and upper monitoring part.

The system block diagram is shown below:

1. PLC control system

PLC control system is divided into PLC control cabinet, operation table and so on. The operation console is equipped with one HP liquid crystal display to realize the whole machine control, operation status indication and feedback of supporting system information. On the operation platform, the control circuit and the main circuit can be powered on and off, start early warning, and start and stop the belt conveyor operation. At the same time, the feedback information of the state of the frequency conversion device, the state of the brake, the state of the discharge point, the tension device and the tape protection device can be observed. The choice of control mode: centralized control automatic / centralized control manual / local, three modes can be converted. In normal production, the centralized control automatic method is used, and the equipment starts and stops automatically in the order and process required by the process. When the centralized control is manual, each device can be operated on the display without locking and linkage. When in place, use button operation on the console.

2. Variable frequency drive part

It is mainly composed of frequency converter, drive part and communication interface, etc. It is used to control the operation of the motor. Receive the control signal from the PLC control system to control the operation of the entire system.

3. Automatic tensioning device

The automatic tensioning device of the belt conveyor is used to tension the belt to the tension when the belt starts. After the tensioning is completed, the ‘power-on signal’ is sent to the console, and the belt conveyor is ready for operation. After the belt conveyor runs normally, the tensioning device automatically maintains the belt tension.

4. Protection system of belt conveyor

Every 50 meters of the belt conveyor is equipped with a two-way pull rope switch, a speed detector, a two-pole deviation switch, a chute blockage detector, a longitudinal tear detector, a material flow detector, smoke, water and other sensors. All control signals are input into the PLC control system, and the PLC control system processes all signals in the control system to judge the operation of the system. Control the operation of the entire system according to the actual situation, and alarm if a failure occurs.

5. The monitoring part of the host computer

Achieve centralized monitoring of the conveyor system of the belt conveyor, real-time monitoring of equipment status and operating parameters, and display of data curves. Perfect information processing function. Alarm information, operating parameters, operation records and other information are automatically formed into a database file in a standard format, and stored on the hard disk for a long time for the information system to call.

The control system has been put into operation in the user unit, and has achieved good results. The entire program control system greatly improves the operation and control level of the equipment. Each operation step of the system can be completed by automatic control in the main control room. Various parameters such as speed, motor temperature and protection status during operation can be displayed on the main control screen. The printer prints out the operating parameters, and the data is easy to consult.