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Paper Transmission Fault Analysis
Time:2016-05-04    Source:    Views:846
    1 Introduction
     Paper Machine electrical transmission control system performance is good or bad is to determine whether a paper machine high efficiency, high-quality production of the premise, then the normal production of a paper machine, in order to ensure continuously high efficiency, high quality be production and maintenance of the transmission system is particularly important, the paper cited the paper machine drive system to maintain in some common faults and gives the relevant analysis and solutions.
Judgment and analysis of machine failure
     As an electrical technician, first managed device have a full understanding of the working principle and design ideas have a very clear understanding. Find out before making a judgment based on analysis of the phenomenon is the right cause of the failure to distinguish from the principle basis.
    General shop operator or maintenance electrician could find just the production process of a surface phenomenon. Such as an operating failure, frequent breaks, threading difficulties. These phenomena are often seen as the operator of electrical failure, often heard complaint is "speed instability." For this complaint electrician to do a second test to see three tests. I saw first spotted the problem and part of the phenomenon of position and comprehensive process analysis the reason; the second test is to observe the speed, current and other parameters were measured to confirm excluded indicating an error; three trials are open-loop or no-load, etc. stand-alone test, to confirm generally range electrical or mechanical failure.
2.1 determine the electrical fault or mechanical failure
 1. electrical fault
    1) the drive can not be started while the load without the presence of stuck or stall situation;
    2) Motor thermal anomaly, even smoke, or current large and small motor does not turn or torque, which may be a line fault or a fault inside the motor;
    3) failure of the operation, acceleration and deceleration does not move, or to reflect the good times and bad is not normal; uneven distribution of the load, but you can adjust the degree of change instability. These may interfere with the line contact or communication-related fault.
2. Mechanical Failure
    1) bearing heating;
    2) the device is rotated abnormal sound, clear sound and can be periodically observed mechanical cycle;
    3) common network portion of mechanical failure is drive roll slippage, the performance of good times and bad for the load distribution, especially abnormal acceleration. Such as friction drive roll slippage after a sudden drop in load current decreases, while the program is to accelerate the operation of a load drop, resulting in accelerating the final drive roll coaster. This situation simply can net some of the tension, if not you can reduce or increase the current limit couch roll drive roll wrap angle.
2.2 difficult to identify the source of fault
     For obvious faults can be resolved directly from the start point of failure, but the actual machine operation is often difficult to determine the source of the problem some anomalies. Common to the following three reasons:
1. Speed instability
     Affect the speed of instability are:
     1) speed sensor (usually encoder) mechanically coupled bad, check the coupling;
     2) Equipment load changes. Open the mechanical coupling device, only the operation of the motor to determine whether interference from machinery and equipment;
     3) speed controller parameters is inappropriate, check and adjust the speed regulator parameters;
     4) the case of the wet end of the paper cited driving, often have high water content of the web, the weight will lead the web when the paper web sagging elongated portion, so that the total division behind too slow, in fact behind the fast transfer speed segment, sagging phenomenon more serious, check the corresponding part of dehydration, and adjusted.
2. The rate of mutation
      Factors affecting the speed of mutation:
      1) speed sensor mechanical connection failure, check the coupling.
      2) point line connection is bad, you should check the wiring.
      3) mechanical equipment failures, such as bearing damage.
 3. To load fluctuation
      Factors affecting the load fluctuations are:
      1) speed sensor mechanical connection failure, check the coupling.
      2) load fluctuation machinery and equipment, mechanical equipment should be opened only run motor coupling, to determine whether interference from machinery and equipment.
Failure analysis of the frequency converter
Cause 3.1 Inverter troubleshooting
3.1.1 motor does not turn Cause
      1) Have access to power, check the power supply;
      2) whether the fault alarm, troubleshooting;
      3) whether the motor fails, check the motor;
      4) drive fault, contact the supplier when the inverter can not be resolved.
3.1.2 motor vibration and a noise, but can not rotate Causes
      1) motor failure;
      2) Inverter fault: The inverter output three-phase voltage imbalance, check the inverter power components for damage, replace if damaged, is still not resolved, contact your supplier. GTR single tube inspection method is to measure the resistance value between the poles with a multimeter. Normal resistance.
3.1.3 Motor overheating fault Cause
      1) overloaded Check mechanical devices for faults;
      2) drive failure, unbalanced three-phase power inverter output, check the GTR element;
      3) Motor failure Check motor cooling fan.
3.1.4 Motor runs unevenly Cause
      1) Coupling mechanical equipment failures, open and mechanical devices, to restart the motor to determine whether interference from machinery and equipment;
      2) If the problem persists, the fault from the drive, first check the three-phase power inverter output is balanced, or whether the output voltage fluctuation; second is to check the output voltage of the rectifier filter capacitor is aging;
      3) speed sensor mechanically coupled bad, check the coupling.
 3.2 protective function of reason
 3.2.1 overcurrent trip
      1) Acceleration time is short, prolonged acceleration, deceleration time;
      2) the mutation load or overload, check the bearing and other mechanical equipment;
      3) the inverter output short-circuit, short-circuit point to find;
      4) external electromagnetic interference, the control signal shield ground is good.
 3.2.2 Fin overheat trip
      1) exhaust fan failure, or heat sink duct obstruction, check and remove;
      2) load increases, inverter overload cause, check the mechanical equipment.
 3.2.3 overload trip
      1) machinery and equipment overload, check the mechanical equipment;
      2) drive failure.
 3.2.4 overvoltage trip
      1) the deceleration time is short, should be extended acceleration and deceleration time;
      2) grid voltage is too high.
 3.2.5 loss of pressure trip
      1) instantaneous power failure, and other motor stops, the inverter is reset, and then start;
      2) undervoltage.
 4 Troubleshooting Application examples
 4.1 Internal dryer breaks
    This obviously can not be considered a vehicle speed reasons, must and process parameters such as steam pressure, the paper quantitatively related to the slurry composition. Even though there may be fluctuations in speed, nor is it important. Therefore, the process should assist staff to find other reasons.
4.2 press section breaks
    A press section breaks is more difficult to determine the failure. In general, it has to be analyzed and judged according to the press in the form of breaks site. If the press is a compound related to the electrical load distribution control error may have occurred, the loss of the balance between the force of the roller, so that the sheet is subjected to abnormal tensile or compressive strength caused by decrease breakage increases. Analyzing the main method is to observe the current indication is normal and swing size. If you find a serious imbalance from the ammeter or unusual swing, debugging should first be empty find the cause of imbalances and adjustment parameters allow the system to stabilize. Easier way is allowed if the load distribution can be stopped one or two motors, it is to let the press part of the multi-load point of the suspected problem stopped, to see if stable. In order to identify a single cause of instability roller. Are some of the specific check:
    1) Each cable for poor contact, especially the associated signal line, such as feedback lines, communication lines, load distribution point between the input and output lines;
    2) PLC program to check on the parameters set by the lower limit is appropriate, there is no computer program errors, program execution is correct and so on;
    3) Check the drive parameters, torque compensation is reasonable to set the default parameters are consistent with the parameters of the motor;
    4) The motor is normal, abnormal noise and abnormal fever. If the above are normal the normal electrical preliminary determination, to observe the process of cause and raw materials.
 4.3 wire and press section junction breaks
    Here for the species and ingredients of a very close relationship between the paper, causes more complex, it is easier to judge the wrong place. Here I have an example to illustrate the practice of commissioning: Sanshui in Guangdong Jinsheng mill a 2640/150 corrugated paper machine had found from the couch roll to press the paper cited frequently breaks phenomenon. Initially skeptical speed change, but repeated testing can not work. The reason is that after the discovery of poor quality and lack of sheet material due to dehydration, the observed phenomenon: the sheet between the couch roll and a pressure within a small range only to maintain balance. If you will find a slight droop drooping slowly length becomes long, resulting in breaks. On the surface it seems to be a speed mismatch, due to slow squeezing the couch roll fast, but the speedometer did not find significant changes observed. The analysis found that, because of a large sheet of water, raw fibers too short. Sheet sag increases because of the relatively large weight, combined with the water is too large, when more than a certain value, sagging sheet portion to form a positive feedback effect, that the greater the drop, the more self-gravity, and so on eventually breaks . On the operating performance is difficult to grasp, found after the press sheet to accelerate sagging, but just to see the sheet will be lifted when pulled off. When the up or down more to accelerate the already too late, it seems on the surface speed failure, would cause an error judgment. This situation requires repeated observations electrician speed and current indication for in-depth analysis to comprehensive judgments. Do not blindly conclusion.
5 Conclusion
    Machine operation, due to mechanical, electrical, are closely linked, some symptom is more obvious, and some hard to fault a moment to acknowledge the fault source is electrically or mechanically. This requires staff to be very familiar with the electrical electrical system, it must also have some knowledge of the relevant papermaking process, a comprehensive analysis of the problem in the face of repeated tests, the best way to find a solution to the problem. Due to space limitations, this article only lists some common faults and analysis, for reference.
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