Siemens, Schneider and Panasonic Servo Drive Repair Common Problems and Solutions
1. 10 cases of Siemens DC servo drive system fault maintenance
example 1. Fault maintenance failure phenomenon of incoming line fast fuse blown: A horizontal machining center equipped with SIEMENS 8MC is turned on after the power grid is suddenly cut off, and the system cannot be started.
Analysis and processing process: After inspection, the incoming fast fuse of the X-axis servo driver of the machine tool has been blown. The feed system of this machine tool adopts SIEMENS 6RA series DC servo drive, and the servo motor and drive device are checked against the drive, and no component damage or short circuit is found.
Check that the mechanical part of the machine tool is also working normally. After directly replacing the fuse, start the machine tool and resume normal work. The reason for the analysis is the occasional failure caused by the sudden power failure of the power grid.
Example 2. Maintenance failure phenomenon of SIEMENS 8MC measurement system failure: a horizontal machining center equipped with SIEMENS 8MC, when the X-axis moves to a certain position, the hydraulic motor is automatically disconnected, and an alarm prompts: the Y-axis measurement system is faulty. Power off and then power on, the machine tool can resume normal work, but the same fault may occur when the X axis moves to a certain position.
Analysis and processing process: This machine tool is an imported horizontal machining center, equipped with SIEMENS 8MC numerical control system and SIEMENS 6RA series DC servo drive. Since the Y-axis alarm occurs when the X-axis moves, in order to verify the correctness of the system, the X-axis measurement feedback cable test was removed, and the X-axis measurement system fault alarm occurred in the system. Therefore, the cause of the system's false alarm can be ruled out.
Check that the X-axis is at and near the position where the alarm occurs, and it is found that it has no interference and influence on the Y-axis measurement system (grating), and only moving the Y-axis has no alarm, and the Y-axis works normally. Then check the Y-axis motor cable plug, grating reading head and grating scale condition, no abnormal phenomenon is found.
Considering that the equipment is a large-scale machining center, there are many cables, and the cable length between the electric cabinet and the machine tool is long, and all cables are fixed on the cable rack and move back and forth with the machine bed. According to the above analysis, it is preliminarily judged that there is a high possibility of local disconnection due to the bending of the cable.
During maintenance, the X-axis was intentionally moved to the position where the fault occurred, the cables were moved artificially, and the connection of each feedback signal line on the Y-axis was carefully measured. Finally, it was found that one of the signal lines occasionally appeared during the continuous movement of the cable. Open circuit phenomenon; after using the spare wire in the cable to replace the broken wire, the machine tool returns to normal.
Example 3~Example 4. The fault phenomenon of following error over-tolerance alarm maintenance caused by drive failure: A CNC gear hobbing machine equipped with SIEMENS PRIMOS system and 6RA26** series DC servo drive system moves the Z-axis of the machine tool after starting up, and the system generates an alarm of "ERR22 following error over-tolerance".
Analysis and processing process: The following error exceeds the alarm of the CNC machine tool, the essence of which is that the actual machine tool cannot reach the commanded position. The cause of this failure is usually the failure of the servo system or the failure of the mechanical transmission system of the machine tool.
Since the servo feed system of the machine tool is a fully closed-loop structure, the test cannot be performed by disconnecting the motor from the mechanical part. In order to confirm the fault location, when the machine is powered off and the clamping mechanism is loosened, the Z-axis lead screw is manually rotated. No abnormality of the mechanical transmission system is found. It is preliminarily determined that the fault is caused by the poor servo system or numerical control device. .
In order to further determine the fault location, when the system is turned on during maintenance, use the handwheel to move the Z-axis a little (the moving distance should be controlled within the maximum allowable following error set by the system to prevent the following error alarm), and measure the DC-axis of the Z-axis. The speed reference voltage of the driver is checked and found that the speed reference has a voltage input, and its value is related to the distance and direction of the handwheel movement. From this, it can be confirmed that the numerical control device works normally, and the fault is caused by the failure of the servo drive.
Check the driver and find that the status indicator of the driver itself has no alarm, which basically eliminates the fault of the main circuit of the driver. Considering that the X and Z-axis drives of the machine tool are of the same model, it is confirmed that the fault location is on the A2 board of the 6RA26** DC drive by exchanging the control boards of the drives one by one.
According to the schematic diagram of the SIEMENS 6RA26** series DC servo driver, check and measure the signals at all levels one by one, and finally confirm that the cause of the failure is caused by the fault of the integrated voltage comparator N7 (model: LM348) on the A2 board: after the replacement, the machine tool recovers normal.
Example 4. Fault phenomenon: an imported horizontal machining center equipped with SIEMENS 850 system and 6RA26** series DC servo drive system, after starting the machine, manually move the X-axis, the machine X-axis table does not move, and the CNC has an X-following error out of tolerance alarm .
Analysis and processing process: Since other coordinate axes of the machine tool work normally, the X-axis driver has no alarm, and all status indicators indicate no fault. In order to determine the fault location, considering that the speed/current adjustment board A2 of the 6RA26** series DC servo driver is the same, During maintenance, the A2 board of the X-axis drive and the A2 board of the Y-axis drive were exchanged. After testing, it is found that the X axis can work normally, but the Y axis follows the out-of-tolerance alarm.
Based on this phenomenon, it can be concluded that the speed/current regulator board of the X-axis drive is bad. According to the schematic diagram of the SIEMENS 6RA26** series DC servo drive, the measurement and inspection found that when the X-axis is moved a small amount, there is an analog input between the speed given input terminals 57 and 69 of the drive. Measure the drive detection terminal B1, the speed analog voltage is correct , but the output of pin 6 of the speed proportional regulator N4 (LM301) is always 0V.
Check the feedback resistors R25, R27, R21 of the speed regulator LM301 one by one against the schematic diagram, the offset adjustment resistors R10, R12, R13, R15, R14, R12, and the input protection diodes V1, V2 of the LM301, given the filter link R1, C1, R20, V14, R27, R28, R8, R3, C5, R4 and other peripheral components in the speed feedback filter link, confirm that all components are faultless.
Therefore, it is confirmed that the cause of the failure is caused by the poor integrated operational amplifier of the LM301; after replacing the LM301, the machine tool returns to normal operation and the failure is eliminated.
Example 5. CNC fault causes follow error out of tolerance alarm maintenance
Fault phenomenon: A CNC gear hobbing machine equipped with SIEMENS PRIMOS system and 6RA26** series DC servo drive system moves the Z axis of the machine tool after starting, and the system generates an alarm of "ERR22 following error out of tolerance".
Analysis and processing process: The fault analysis process is the same as the previous example, but in this example, when the handwheel is used to move the Z axis a small amount, the speed of the Z-axis DC drive is measured and the given voltage is always 0, so it can be preliminarily determined that the fault is in the numerical control device or numerical control device. on the connection cable to the drive.
Check that the cable connection between the CNC device and the driver is normal, and confirm that the cause of the fault is in the CNC device. Turn on the numerical control device to check and find that the digital input of the D/A converter of the Z-axis speed reference output is correct, but there is no analog output, thus confirming that the fault is caused by a bad D/A converter.
After replacing the 12-bit D/A converter DAC0800 of the Z-axis speed reference output, the machine tool recovers
Example 6. Fault phenomenon: A CNC gear hobbing machine equipped with SIEMENS PRIMOS system and 6RA26** series DC servo drive system will alarm "ERR21, Y-axis measurement system error" after it is turned on.
Analysis and processing process: The reasons for the occurrence of measurement system alarms in the CNC system are generally as follows:
1) The position feedback signal interface circuit of the numerical control device is defective.
2) The connection cable between the numerical control device and the position detection component is defective.
3) The position measurement system itself is not good.
Because the servo drive system of this machine tool adopts a fully closed-loop structure, the detection system uses the grating of HEIDENHAIN Company. In order to determine the fault location, the speed of X and Y axes output by the numerical control device is first given during maintenance, and the drive enable and the position feedback of X and Y axes are exchanged, so that the output of the X axis of the numerical control controls the Y axis, and the output of the Y axis Controls the X axis. After the adjustment, operate the numerical control system, manually move the Y axis, the X axis of the machine tool moves, and the work is normal, which proves that the position feedback signal interface circuit of the numerical control device is faultless.
However, when the CNC system is operated and the X axis is moved manually, the Y axis of the machine tool does not move, and the CNC displays an alarm of "ERR21, X axis measurement system error". It is thus confirmed that the alarm is caused by the fault of the position measurement system and has nothing to do with the interface circuit of the numerical control device. Check that the cable connection of the measurement system is correct and reliable, and the problem of the cable connection is ruled out.
Use an oscilloscope to check the output waveforms of Ual and Ua2, *Ua1 and Ua2 of the preamplifier EXE601/5-F of the position measurement system, and it is found that the Ua1 phase has no output. Further check the signal waveform of the grating output (input of the preamp EXE601/5-F), and found that Ie1 has no signal input. Check that the grating of the machine tool is installed correctly, and confirm that the fault is caused by the bad grating: after replacing the grating LS903, the machine tool resumes normal operation.
Example 7. Fault phenomenon: A CNC gear hobbing machine equipped with SIEMENS PRIMOS system and 6RA26** series DC servo drive system will alarm "ERR21, X-axis measurement system error" after it is turned on.
Analysis and processing process: The fault analysis process is the same as the previous example, but in this example, the Ual and Ua2, *Ual and *Ua2 output waveforms of the preamplifier EXE601/5-F of the position measurement system are checked with an oscilloscope, and it is found that the same Ual has no output. . Further check the signal waveform of the grating output (input of the preamplifier EXE601/5-F), and find that Ie1, the signal input is correct, confirm that the fault is caused by the bad preamplifier EXE601/5-F.
According to the principle of EXE601/5-F (see below), the signal of the preamplifier EXE601/5-F was measured step by step, and it was found that one of the LM339 integrated voltage comparators was defective; after the replacement, the machine tool returned to normal operation.
Example 8. The drive is not ready for fault maintenance. Fault phenomenon: a horizontal machining center equipped with SIEMENS 850 system and 6RA26** series DC servo drive system suddenly stops during the processing process, and the "drive fault" indicator on the rear panel of the startup is on. The machine cannot start normally.
Analysis and processing process: According to the phenomenon that the "drive fault" indicator light on the panel is on, combined with the electrical schematic diagram of the machine tool and the analysis of the system PLC program, it is confirmed that the fault of the machine tool is that the Y-axis drive is not ready.
Check the driver in the electric cabinet, measure the main circuit power input of the 6RA26** driver, only the V phase has voltage, and further check according to the electrical schematic diagram of the machine tool, and find that the U and W phases of the 6RA26** driver incoming line quick fuse are blown. Use a multimeter to measure the 1U and 1W of the main circuit input terminals of the driver to confirm that there is a short circuit inside the main circuit of the driver.
Since the incoming line of the main circuit of the 6RA26** AC drive is directly connected to the thyristor, it can be confirmed that the fault is caused by the damage of the thyristor.
Measure the main circuit thyristors V1-V6 one by one, and confirm that V1 and V2 are bad (short-circuited); after replacing the spare parts of the same specification, the machine tool returns to normal.
Since the other parts of the driver are not faulty, after replacing the thyristor module, the machine tool resumes normal operation, and the analysis may be caused by accidental faults caused by instantaneous voltage fluctuations or load fluctuations.
Example 9. The phenomenon of fault maintenance that the motor does not rotate due to external faults: An imported vertical machining center equipped with SIEMENS 6M system found that the tool magazine could not rotate normally during the tool change process.
Analysis and processing process: Through the analysis of the electrical schematic diagram of the machine tool, the tool magazine rotation control of the machine tool adopts the 6RA** series DC servo drive, and the tool magazine speed is manufactured by the machine tool manufacturer. †board for control.
On-site analysis and observation of the tool magazine rotation action found that when the tool magazine was rotated, the PLC rotation signal had been input, the tool magazine mechanical pin had been pulled out, but the conversion given analog quantity of the 6RA26** driver had not been input. Since the output of the analog quantity comes from the "tool magazine given value conversion/positioning control" board, the schematic diagram of the "tool magazine given value conversion/positioning control" board provided by the machine tool manufacturer is measured step by step, and finally it is found that the The analog switch (model DG201) is damaged. After replacing the same model spare parts, the machine tool resumes normal operation.
Example 10. The fault maintenance phenomenon that the motor is turned on at a high speed: a machine tool of the same model as Example 268, during startup and debugging, after manually pressing the tool magazine rotation button, the tool magazine rotates at a high speed, causing the machine tool to alarm.
Analysis and processing process: According to the fault phenomenon, it can be preliminarily determined that the fault is caused by the incorrect polarity of the speed measurement feedback of the DC drive of the tool magazine or the positive feedback or open loop of the speed loop caused by the falling off of the speed measurement feedback line. The measurement confirms that the speed measurement feedback line of the servo motor is connected, but the polarity is incorrect; after the polarity of the speed measurement feedback is exchanged, the action of the tool magazine returns to normal.
2. Common fault analysis and solutions of Schneider servo drives
1. The servo motor does not run when there is pulse output, how to deal with it?
â‘ Monitor the current value of the pulse output of the controller and whether the pulse output light is flashing, and confirm that the command pulse has been executed and the pulse has been output normally;
â‘¡ Check whether the control cable, power cable and encoder cable from the controller to the driver are wrongly wired, damaged or have poor contact;
â‘¢ Check whether the brake of the servo motor with brake has been opened;
â‘£ Monitor the panel of the servo drive to confirm whether the pulse command is input;
⑤ The Run command is normal;
â‘¥ The control mode must select the position control mode;
⑦ Whether the input pulse type set by the servo drive is consistent with the command pulse setting;
⑧ Make sure that the drive prohibition signal on the forward rotation side, the drive prohibition signal on the reverse rotation side and the reset signal of the deviation counter are not input, the load is disconnected and the no-load operation is normal, and the mechanical system is checked.
2. The motor deviation counter overflow error occurs when the servo motor rotates at high speed, how to deal with it?
â‘ Motor deviation counter overflow error occurs when rotating at high speed;
Countermeasures:
Check whether the wiring of the motor power cable and the encoder cable is correct and whether the cables are damaged.
â‘¡ The motor deviation counter overflow error occurs when a long command pulse is input;
Countermeasures:
a. The gain setting is too large, manually adjust the gain again or use the automatic gain adjustment function;
b. Extend the acceleration and deceleration time;
c. If the load is too heavy, it is necessary to re-select a larger capacity motor or reduce the load, and install a transmission mechanism such as a reducer to improve the load capacity.
â‘¢ The motor deviation counter overflow error occurred during operation.
Countermeasures:
a. Increase the set value of the overflow level of the deviation counter;
b. Slow down the rotation speed;
c. Extend the acceleration and deceleration time;
d. If the load is too heavy, it is necessary to re-select a larger-capacity motor or reduce the load, and install a transmission mechanism such as a reducer to improve the load capacity.
3. The servo motor reports overload without load, how to deal with it?
â‘ If it happens when the servo Run signal is connected and there is no pulse:
a. Check the wiring of the servo motor power cable and check whether there is poor contact or cable damage;
b. If it is a servo motor with a brake, be sure to open the brake;
c. Whether the speed loop gain is set too large;
d. Whether the integral time constant of the speed loop is set too small.
â‘¡ If the servo only happens during operation:
a. Whether the position loop gain is set too large;
b. Whether the positioning completion amplitude is set too small;
c. Check that there is no stall on the servo motor shaft and readjust the machine.
4. How to deal with abnormal sound or jitter when the servo motor is running?
â‘ Servo wiring:
a. Use standard power cables, encoder cables, control cables, and whether the cables are damaged;
b. Check whether there is an interference source near the control line, and whether it is parallel to or too close to the nearby high-current power cable;
c. Check whether the potential of the grounding terminal has changed, and ensure that the grounding is good.
â‘¡ Servo parameters:
a. The servo gain setting is too large, it is recommended to re-adjust the servo parameters manually or automatically;
b. Confirm the setting of the time constant of the speed feedback filter, the initial value is 0, you can try to increase the setting value;
c. The electronic gear ratio setting is too large, it is recommended to restore to the factory settings;
d. For the resonance of the servo system and the mechanical system, try to adjust the frequency and amplitude of the notch filter.
â‘¢ Mechanical system:
a. The coupling connecting the motor shaft and the equipment system is offset, and the installation screws are not tightened;
b. Poor engagement of pulleys or gears will also cause load torque to fluctuate. Try no-load operation. If no-load operation is normal, check whether there is any abnormality in the joint part of the mechanical system;
c. Confirm whether the load inertia, torque and rotational speed are too large, and try to run without load. If the no-load operation is normal, reduce the load or replace the driver and motor with larger capacity.
5. The positioning of Schneider servo motor is inaccurate for position control, how to deal with it?
â‘ First confirm whether the current value of the pulse actually sent by the controller is consistent with the expected value, if not, check and correct the program;
â‘¡ Monitor whether the number of pulse commands received by the servo drive is consistent with that sent by the controller, and if not, check the control cable.
Three, Panasonic servo drive maintenance common problems and solutions
1. Panasonic digital AC servo system MHMA 2KW, when the machine is powered on, the motor vibrates and makes a lot of noise, and then the driver has alarm No. 16, how to solve it?
This phenomenon is generally caused by the self-excited oscillation caused by the high gain setting of the driver. Please adjust parameters No.10, No.11, No.12, and appropriately reduce the system gain. (Please refer to the content of gain adjustment in the "Instruction Manual")
2. Alarm No. 22 appears when the Panasonic AC servo drive is powered on, why?
The No. 22 alarm is an encoder fault alarm, and the causes are generally:
A. There is a problem with the encoder wiring: disconnection, short circuit, wrong connection, etc., please check carefully;
B. There is a problem with the encoder on the motor: dislocation, damage, etc., please send it for repair.
3. When the Panasonic servo motor runs at a very low speed, it is fast and slow, like crawling, what should I do? The low-speed creeping phenomenon of the servo motor is generally caused by the low system gain. Please adjust the parameters No.10, No.11 and No.12, adjust the system gain appropriately, or run the automatic gain adjustment function of the drive. (Please refer to the content of gain adjustment in the "Instruction Manual")
4. In the position control mode of the Panasonic AC servo system, the control system outputs pulse and direction signals, but whether it is a forward rotation command or a reverse rotation command, the motor only rotates in one direction, why?
In the position control mode, the Panasonic AC servo system can receive three control signals: pulse/direction, positive/reverse pulse, and A/B quadrature pulse. The factory setting of the drive is A/B quadrature pulse (No42 is 0), please change No42 to 3 (pulse/direction signal).
5. In the use of Panasonic AC servo system, can servo-ON be used as the signal to control the motor offline, so as to directly rotate the motor shaft? Although the motor can be offline (in a free state) when the SRV-ON signal is disconnected, do not use it to start or stop the motor, frequent use of it to switch the motor on and off may damage the drive. If the offline function needs to be realized, it can be realized by switching the control mode: if the servo system needs position control, the control mode selection parameter No02 can be set to 4, that is, the first mode is position control, and the second mode is torque control. . Then use C-MODE to switch the control mode: when performing position control, turn on the signal C-MODE to make the driver work in the first mode (ie position control); when it needs to be offline, turn the signal C-MODE on, Make the driver work in the second mode (that is, torque control), because the torque command input TRQR is not wired, so the motor output torque is zero, so as to realize offline.
6. The Panasonic AC servo used in the CNC milling machine developed by us works under the analog control mode, and the position signal is fed back to the computer by the pulse output of the driver. When debugging after the machine is installed, a motion command is issued, and the motor will fly. What is the reason?
This phenomenon is caused by the wrong phase sequence of the A/B quadrature signal fed back to the computer by the pulse output of the driver, resulting in positive feedback. The following methods can be used to deal with it:
A. Modify the sampling program or algorithm;
B. Swap A+ and A- (or B+ and B-) of the pulse output signal of the driver to change the phase sequence;
C. Modify the driver parameter No45 to change the phase sequence of its pulse output signal.
7. In a testing equipment developed by us, it is found that the Panasonic AC servo system has some interference to our testing device. What method should be taken to eliminate it? Because the AC servo drive adopts the inverter principle, it is a relatively prominent source of interference in the control and detection system. In order to weaken or eliminate the interference of the servo drive to other electronic equipment, the following methods can generally be used:
A. The ground terminals of the driver and motor should be grounded reliably;
B. Add isolation transformer and filter to the power input end of the driver;
C. Use shielded wires for all control signal and detection signal wires.
The problem of interference is a very difficult problem in electronic technology. There is no fixed method to eliminate it completely and effectively. Usually, anti-interference measures are found by experience and experiments.
8. Why does the servo motor not lose steps? The servo motor driver receives the feedback signal of the motor encoder and compares it with the command pulse, thus forming a position semi-closed loop control. Therefore, the servo motor will not lose steps, and each command pulse can be reliably responded.
9. How to consider the power supply of Panasonic servo? At present, almost all Japanese-made AC servo motors are powered by three-phase 200V, and the domestic power supply standards are different, so it must be solved according to the following methods:
A. For AC servos below 750W, in general, single-phase 220V can be directly connected to the L1 and L3 terminals of the drive;
B. For other types of motors, it is recommended to use a three-phase transformer to convert three-phase 380V into three-phase 200V, and connect to L1, L2, and L3 of the drive.
10. What should be paid special attention to when mechanically installing the servo motor?
Since a rotary encoder is installed at the rear end of each servo motor, it is a very fragile precision optical device, and excessive impact force will definitely damage it.
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