Process requirements
1. A paper machine consists of several parts, including the headbox, wire section, press section, drying section, calendering section, and winding section. The main drive electrical control system is a speed chain coordination system composed of multiple drive points.
2. A fixed transmission ratio must be maintained between each transmission point to ensure that the linear speed of each transmission point is consistent. This facilitates the acceleration and deceleration of the equipment and prevents paper breakage or paper accumulation due to large differences in linear speed between transmission points.
3. The speed control accuracy requirement for the transmission system of low-speed paper machines is 0.1%, and the frequency control accuracy is usually required to be 0.01Hz.
4. Analog signals are susceptible to electromagnetic interference, affecting the transmission accuracy and stability of the paper machine. To improve the system's accuracy and stability and enhance its anti-interference capability, the system uses a PLC as the main control unit. Acceleration and deceleration at each stage are controlled by buttons. The acceleration, deceleration, and speed transmission ratio at each transmission point in the speed chain are calculated and controlled by the PLC. Speed adjustment commands are sent to the frequency converter via RS485 communication in data mode.
System Configuration
The SINE303 series open-loop vector control frequency converter , N units, features high transmission accuracy, good dynamic performance, and fast response speed.
System main control unit: Mitsubishi FX2N series PLC, with 485 communication module and D/A module.
All transmission points in the system are controlled in an open-loop speed control mode, with speed control commands issued by the PLC.
System Features
1. The electrical control system adopts an open-loop control method, which has a simple structure, clear control logic, safe and reliable use, and convenient operation and maintenance.
2. Current-type vector control frequency converter, with flexible speed control, fast response, high efficiency and good dynamic performance.
3. The frequency accuracy of the variable frequency drive is 0.01Hz, the system speed regulation accuracy is high, and there is no drift and zero error.
4. PLC control is adopted to accurately calculate the speed transmission ratio of each stage. The speed coordination control between each transmission point is highly accurate, and there will be no paper breakage or paper stacking.
5. The communication method enables fully digital control of the system, with strong anti-interference ability and no signal attenuation.
6. The system automatically stores the current speed of each level during operation. When restarting after a shutdown or power outage, the system will run at the speed before the shutdown, without the need to readjust the set speed of each level of the frequency converter .
