Paper Machine Servo System Design and Modification Plan
First, the generous statePaper-making enterprises with high energy consumption per ton of paper companies that can power more than 500 degrees, power consumption is very serious power. Traditional paper-making machine using SCR DC converter (power), frequency and motor slip (low power) transmission, in the production process, often due to mechanical wear, belt slippage and other factors caused the speed to match the offset form breaks thickness disparities. In order to reduce energy consumption, optimize product quality, improve labor productivity, modern papermaking equipment and more multi-segment motor drive, installing the AC motor or servo motor drive in each division and formulated appropriate special servo drive, requiring all Division It can not only achieve synchronization control, and can speed within a certain range. All-digital control system enables automation equipment to the next level, it's unique full-line monitoring system allows the production status of the user is very clearly understand the device.Second, the program design1, the papermaking processThe basic components of papermaking machinery into the order paper formed wire part, the press, before drying, after pressing, drying, calender, a reel machines. Its technology for the pulp in the headbox output wire section dewatering molding, compression in the press section of the paper layer even after drying before drying, and then press enter after sizing, and then into the dryer after the drying process, and then use calender smoothed the paper, the final form of the parent roll by the reel.2, the control programPaper machine drive control system is a constant speed, constant load substantially constant speed system. From the control characteristics can be divided into: speed control, torque control, load distribution control three basic control mode, the control requirements for the long-term rate stability, dynamic recovery time as short as possible. According to the paper machine object properties. Control scheme can be summarized as multidivisional synchronous speed control chain control, load distribution control segment control systems for both typical structure. Load Distribution Control Division, the program is usually applied on large paper making equipment, it has the power wire speed advantages, but the high cost of the control system is not suitable for small and medium paper machine. Multi-division synchronous speed control using constant-torque motor and vector servo drive system to achieve synchronization machine to achieve synchronous speed, while using vector closed-loop servo drive system control functions to correct the speed of the device division by load changes caused by the change. It has a wide speed, low cost, cost advantages, and more for small and medium sized paper making machine. Here we introduce specific multidivisional synchronous speed transmission used on the paper machine:
Formed from the pulp to the paper machine paper, and subject to multiple segments, so the speed of a multi-unit coordinate system. Speed between each segment with demanding, according to the process, usually have the relationship shown in the following table, as long as one segment speed instability, will not sustain the production of the paper web is not broken, that is loose down. If the entire machine speed instability, there is no guarantee of weight paper (weight per square meter sheet) unchanged. Thus requiring various branches of machine speed can steady speed. And meet certain ratio between the speed of each segment; you should adopt multidivisional synchronous speed chain control system.Ratio of speed paper machine generally of the divisionsRatio papermaking machine of the divisionsPart NamesIn sticky paste made of paperCouch 89-91 94-95.5First press 94-9696-97The second press 97-98 97.5-98Third press 98.5-99 98.5-99Drying section 100 100Calender 100.05-100.15 100.05-100.15Coiler 100.10-100.30 100.10-100.301. Multi-division synchronous speed chain control principleSuppose there are n TRANSMISSION OF PAPER MACHINE divisions, divisions speeds are: N1, N2, ..., Nn, two adjacent segments are speed ratio K1, K2, ..., Kn-1, you may have the following relationship:
N2 = K1N1N3 = K2N2 = K2K1N1N4 = K3N3 = K3K2K1N1... ... ...Nn = Kn-1Nn-1 = Kn-1 ... K1 N1
Where N1 is the speed of the first transmission point, also known as line speed. Changing the line speed N1, the rest of the drive point velocity N2, ..., Nn will follow in proportion to changes, but changes the speed ratio Ki (i = 1,2, ..., n-1), only the i-th transmission point behind the drive speed will change each transmission speed point before i will not change.
For example: the adjustment ratio K3, transmission speed N4, N5, ... Nn will change, but the N1, N2, N3 does not change.2. Multi-division synchronous speed chain control system
Features of this system is that there is only the relationship between the transmission ratio points, no-load distribution control. Such a system is relatively simple, to meet a variety of paper and servo drive system combining needs, synchronous speed chain may be analog speed chain, digital speed chain speed chain and PLC program type, the following illustrate the principle.1) Analog speed chainThis speed DC drive chain era has been adopted, following the principle shown in FIG.Where N1 is the line speed, only the first transmission line speed change points, the remaining points can only fine-tuning, the range of between about 5% -10%. Advantages simulation speed chain is simple, flexible, low cost, disadvantage is poor anti-interference ability, when using long signal lines is limited, there is a difference reliability, insufficiency and other shortcomings.
2) PLC procedural speed chain
For large multi-machine drive points can solve differential analog speed chain reliability insufficiency and other issues. The controller uses imported programmable logic controller (PLC) as the control center of the scene, all of the input control device switches to protect the output point contacts and out through optical isolation PLC, effectively shield the interference signal field, the central processor running reliable operation is guaranteed. The original part of DC electric drive or inverter. Reconstruction will adopt a PLC + human-computer touch screen controller for central control of multiple servo drive system all-digital control system (see Figure 1). Depending on the specific control requirements of the design control program are as follows:
(1) PLC of eight special servo drive system uses a closed-loop vector control, thus increasing boot capacity servo drive system control accuracy and speed of the system to achieve stepless online (see Figure 2). Among interconnected synchronous motor, servo drives with synchronous acceleration and deceleration function.
(2) to adjust the speed of the machine can be produced on-site operator input on the touch screen digital is complete. Equipment production speed is determined by the following formula:
Where: f is the frequency of operation of the motor slip coefficient δ κ mechanical gear ratio p motor pole pairs
By the above formula to calculate the speed of production equipment.The same method (3) also can be implemented independently of each segment of the motor speed control and manual bias correction.
(4) the use of PLC and vector motor is running between the closed-loop control to ensure absolute synchronization between the motor, in case of mechanical or other causes of a segment of the motor speed drift or sudden load changes, the system will automatically follow the instruction of other motor, thereby reduce the chance of breaks, improve paper quality.
(5) provided with tension detection system, automatically adjusting the tension according to the motor speed.
(6) To facilitate equipment maintenance system is provided to move the crawl function can operate independently of each segment, the same speed can be freely set.(7) to retain the original control system functions and operations.
(8) also has alarm system, process-related data for each motor speed and other display functions. (Fig. 3)
(9) also has a man-machine alarm recording, production statistics, uptime and other production-related data recording function (Fig. 4)Figure IFigure IIFigure IIIFigure IVThird, the principle
When the system receives a signal to run, first detected electrical equipment operation necessary conditions are met, if not meet the system will automatically output the appropriate signal to drive the power source of these signals, within a set period of time can not meet the system requirements to run the system will automatically give a warning prompt that asks the user to troubleshoot.
System start conditions are satisfied the system will be based on the machine speed set by the user and the operating frequency of the motor 8 basic operating frequency operation, calculated by the PLC operating frequency transmitted to the servo drive system to control the motor according to the technological requirements of the order start the corresponding motor, all motors start after the completion of all the equipment into the normal working state, and the system will be based on feedback to the system to trace the final output speed to compensate, so that the equipment is operated in synchronization state, the system is provided with a tension feedback device, real-time collection sheet tension, according to the actual condition and then automatically adjust the operating frequencies of the motor, so as to reduce the chances of a web break. In the case of the system is running a severe failure alarm system will be automatically stopped when the front end of the motor, the rear end of the motor fault is not reset or system does not receive a signal will stop automatically shutdown after running for some time. The process starts with the system down opposite process.Fourth, the advantage of the transformationChain 1, the system include: safety chain, technology chain, the chain start and stop the chain, the chain breaks, the fault chain.
2, servo-driven system to replace DC converter can reduce energy consumption. Advanced tension control system and method of synchronization accuracy has been greatly improved, the quality of the paper production equipment to provide a strong technical support. Easy to adjust the machine speed, smooth, wide speed range, the line speed adjustment range of up to 0-800m / min. Acceleration, deceleration synchronization, can meet a variety of production requirements.
3, each segment speed and ratio can be adjusted independently, the system software will load automatically adjust the torque of the motor based on the load distribution than intelligent analysis to ensure equipment in any of the divisions between the load a segment changes ratio does not exceed the required range; speed up and down the various branches of fine-tuning, and independently of each other.
4, the system has a maintenance mode segment jog crawl function.5, simple scientific and intuitive. Site equipment working conditions Online simulation, allowing users like exposure to the shop floor.
6, to provide long production data records for production and management arrangements provide the basis for understanding the production schedule. Fault recording function provided by the system can be more convenient user maintenance, troubleshooting tips for the maintenance personnel can repair the specified direction.
7, on-line real-time monitoring is more conducive to product quality control and understand the equipment running status, provided reference data for future maintenance work. All operations are password-protected, you can do the actual operator level, respectively, and are authorized to set a different password.
8, the device also enables remote management capabilities, the system uses the international standard communication protocol for the full automation of the future of enterprises provides a good compatibility.