1 Introduction In the application of the frequency converter, it is often necessary to contact the commissioning and maintenance, and the faults that occur due to various reasons need to be eliminated in time, the correct debugging method, the timely detection of the fault, and the accurate determination of the cause of the fault, in addition to having certain In addition to theoretical knowledge, there are two basic qualities, that is, one must be familiar with products, and the other is to accumulate practical experience in debugging, maintenance, and troubleshooting. These theoretically not deep practical experience depends on work practice. In addition to the accumulation of time, extensive exchanges with peers is a very good channel. I share my practical experience with readers, in order to promote the technical exchanges between the frequency converter colleagues, and play a role in attracting jade.
2 Inverter and host computer communication fault judgment and elimination 2.1 Example 1 (1) Fault phenomenon: Customer calls technical service telephone report obstacle: 40 sets of 22kw fan in a factory workshop for energy-saving renovation, each inverter is equipped with a host computer The ddc module performs communication control (Imported from Canada). The upper computer mainly controls the fault alarm of the frequency converter, the alarm of the filter network, the frequency, the start and stop, and the temperature. The user reflects that the wiring is normal, and can run normally when disconnected from the upper computer. When it is connected with the upper computer, the upper computer can not stop when the inverter stops the command.
(2) Fault analysis and judgment: To the on-site inspection system, the fault is as described by the customer. View the description of the ddc module of the host computer, and find that the dry contact of the ddc module is the transistor output, the output voltage is DC 24v, and the inverter only receives passive signals or switch signals, so the above fault phenomenon will appear.
(3) Troubleshooting: Adding a DC 24V relay to the signal output of the ddc module solves this problem.
2.2 Example 2 (1) Fault phenomenon: The user telephone reported that: “The inverter can run when the inverter control system is not connected to the host computer, but it cannot be operated as long as it is connected to the host computer.â€
(2) Fault analysis and judgment: According to the empirical analysis, the host computer gives the running signal, but the inverter does not receive it. The meter is also used to measure the upper computer. Therefore, it is judged that the line fault is abnormal, and the user technician is instructed to re-route the line. Check it carefully.
(3) Troubleshooting: Later, the user called the feedback and said: "It is the one-way control line that is not securely connected. After the connection is completed, the fault is eliminated."
2.3 Example 3 (1) Fault phenomenon: A direct user of a dealer has an old jump fault of the Lenze 5.5kw inverter. The inverter was sent out for overhaul twice and did not find the problem. If it was returned to the company, it could not be used. The fault still exists.
(2) Fault analysis and judgment: The situation is as follows: All the inverters of this equipment are controlled by communication with the host computer, and there are many control lines. The temperature of the site is also very high. The equipment has been used for several years without maintenance. Over. According to these factors, it is suspected that the line has a short circuit or an open circuit. First remove all the control lines of the faulty inverter, remove the motor line, and run the inverter without load. At this time, it is normal to run the inverter. It is normal to run the inverter after connecting the motor, but connect the control line. Reporting the fault protection, I will definitely have a bottom in this step.
(3) Troubleshooting: All the control lines are measured with the meter. Finally, two control lines are aging and short-circuited. The other control lines also have different degrees of aging, but they are not so serious. After all the control lines are replaced, the equipment runs normally.
2.4 Example 4 (1) Fault phenomenon: The user reflects that the touch screen on the CNC lathe is interfering with the inverter. After the lathe is running normally, the touch screen often turns on the screen or turns into a blue screen. The data is not visible, as long as the power is turned off and then sent to the system. The fault is gone. After the device runs for a few minutes, the fault starts to appear again. The user requests technical support and on-site processing.
(2) Fault analysis: After arriving at the site, it is found that the inverter is controlled by the touch screen. Check the wiring of the inverter, the external control circuit and the equipment are all normal. After replacing the inverter, the fault still exists. Later, the control line was replaced by a shielded line to reduce the carrier frequency of the inverter, and the fault was still not solved. Finally, only from the touch screen, the power cord on the touch screen is removed and plugged in again, the fault is gone. After a few minutes, the fault occurred, and all the signal cable plugs on the touch screen were removed, and the fault still existed. I don’t know how to start this kind of thing.
(3) Troubleshooting: At this time, I suddenly thought that I missed the grounding wire of the touch screen case. When the ground wire was removed, the device did not malfunction after running for several hours. The measurement is caused by interference caused by poor grounding, and the grounding resistance is relatively large.
3 Inverter installation environment fault judgment and elimination 3.1 Example 1 (1) Fault phenomenon: A 55kw inverter, after more than one year, when power is applied, the undervoltage "poff" is reported. When the 380v power supply test is passed, the contactor is found. After the suction, there is a "beep". When the power is turned off, the 220v transformer inside the inverter is damaged, and the two 220v fans are burned out.
(2) Cause of failure: After the inspection by the maintenance center, the fault is caused by the aging of the AC fan and the transformer pressure is burnt out. The air duct and fan of the inverter have a lot of oil and dust, which causes the fan to age and the contactor to be poorly coupled. Therefore, it is very important to improve the working environment of the inverter!
3.2 Example 2 (1) Fault phenomenon: A 110kw inverter of a textile factory is used on the air compressor, and the pid is used for closed-loop control. After using it for a while, the power is not displayed, and it is found that the inverter control board has burned out. The dealer's technician changed the control panel to the user's site or burned it out. The user was very anxious and made several calls to the company.
(2) Fault handling: After the scene is checked, the inverter is normal, the main circuit wiring is also normal, and a short circuit is found when measuring the control line. The system is normal after replacing the control line.
(3) Fault reason: The control line of the inverter is not a wire trough, but is randomly routed from the ground. This is a low-level error. Remove the control line and observe that there are many damages, all of which are crushed by hard objects and cause a short circuit.
3.3 Example 3 (1) Fault phenomenon: A 160kw inverter of a coal mine enterprise, with the load running old skipped load protection, no problem with no-load operation, using the meter to measure the output three-phase voltage of the inverter is also balanced. This machine has been used for two years, not within the warranty, and we are still rushed to the scene to deal with the fault.
(2) Fault check: measuring the external circuit, console and inverter with a multimeter is normal; the input and output three-phase current is also normal with the clamp-type watch clamp; there is no problem in measuring the current detection circuit on the power supply board. Where is the fault?
(3) Fault reason: I thought about whether the Hall sensor would have any problem. The Hall sensor resistance was normal. Finally, only the Hall connection line was not checked. The Hall connection line was removed and measured with a multimeter. A signal was found. The line is broken. After the repair, the inverter runs normally and the fault is removed.
(4) Handling suggestions: This field inverter is installed next to the motor and the vibration is relatively large, so this kind of failure occurs.
3.4 Example 4 (1) Fault phenomenon: Received a customer's telephone and said: "With our company's 15kw inverter, it has been more than a year. Now the inverter runs for a period of time and the heat is serious, and it is required to return to the company for maintenance."
(2) Fault analysis: Instruct the customer technician to check whether the motor has heat. After checking the motor, it also generates heat. The technician is required to measure the insulation resistance of the motor to the ground with a megohmmeter; replace the inverter with another good motor. Then observe whether the motor has any heat.
(3) Fault reason: After the customer replaces the motor, the situation is normal. The original motor insulation resistance is measured with a megohmmeter, and the resistance is not normal. This indicates that the inverter is not a problem, but the motor has a problem, and the insulation resistance value is long. Become smaller.
4 Inverter interference fault judgment and elimination 4.1 Example 1 (1) Fault phenomenon: When a user reports that the plc controls the inverter, unnecessary fault information often occurs. For example, the inverter does not receive the signal after the signal is issued by plc, or the inverter malfunctions. As the customer was more anxious and affected the production, we received the feedback and immediately rushed to the scene for processing.
(2) Fault reason: The inverter, plc, and equipment are inspected on site, and it is judged by interference based on experience.
(3) Troubleshooting: first connect the filter to the input of the switching power supply module of plc. The problem is still no obvious improvement. Later, the power cable and control line of the inverter and the plc are separately routed, and some shielding measures are taken. There is a significant improvement in system failure.
4.2 Example 2 (1) Fault phenomenon: A customer reflects that three inverters are installed in the same frequency conversion cabinet to form a speed control system, and the external potentiometer is used for speed regulation. However, when the frequency is adjusted, the frequency fluctuates greatly. The frequency of one inverter and the other inverter frequency also change, and then the fault protection will be reported.
(2) Fault reason: After the scene is checked, the power supply, load, potentiometer and control circuit are all normal. When debugging the inverter, when one inverter runs separately, it works normally. When two or three units are running at the same time, An exception will occur.
(3) Troubleshooting: Judgment is caused by interference. Move the three inverters out of the inverter cabinet and install them in a separate frequency conversion cabinet. The potentiometers are also separately routed. All control lines are replaced with shielded cables. At this time, three inverters are used. The device can run at the same time, indicating that the fault is judged accurately.
4.3 Example 3 (1) Fault phenomenon: A user's telephone feedback, the main motor of a printing press and the paper feeder motor are regulated by a frequency converter. When the main motor inverter is running separately, the printing machine equipment works normally. When the main motor inverter and the paper feeder inverter run synchronously, the software over-current fault is reported. The dealer technician went to the site for a day. If it was not adjusted, it was determined that the inverter had a problem and could not be returned.
(2) Fault reason: After we went to the site, we found no problems with the inverter and equipment. Observe the running status of the two inverters of the printing machine, and find that the main motor inverter and the paper feeder inverter are normal when they are running separately, that is, the main motor inverter and the paper feeder inverter are reported to be fault-protected when they are running synchronously. Since all the movements of this printing machine work through contactors and relays, and the printing machine equipment is not grounded, the grounding of the inverter is of course taken from the printing machine equipment, so we judge that it is caused by interference.
(3) Troubleshooting â— Replace all control lines with shielded wires and add magnetic rings;
â— Add the magnetic ring to the main circuit power line of the inverter input and output;
â— Ground the printing press equipment and the inverter independently.
After the above measures are taken, the fault is removed and the system returns to normal.
4.4 Example 4 (1) Fault phenomenon: Three 15kw inverters on a textile machine always jump "hardware protection" fault. Moreover, it is not reported at the same time. Occasionally, one of the faults will be reported during operation, and it will be able to operate normally after reset.
(2) Fault analysis and judgment: The static test inverter has no problem, and the main line and control line are also intact. Using a multimeter to measure the neutral and ground is the same. Ask the electrician to know that their factory wiring is shared by zero ground, and the fault may be here. The inverter reports "hardware protection" faults generally as follows:
â— There is a short circuit on the three-phase output side of the inverter;
â— The inverter module is damaged;
â— The external interference signal enters the inverter.
(3) Troubleshooting: Since the first and second reasons are normally eliminated, there is only a third external interference signal. The interference signal enters the inverter from the ground line, and the ground line is shared by zero ground. Therefore, if the ground line is removed, the interference source is cut off. At this time, the inverter is running normally.
4.5 Example 5 (1) Fault phenomenon: A dealer user telephone reflects that a 3.7kw inverter is used on a 4kw bell weaving machine. After several hours of operation, the motor does not turn, the frequency converter has frequency display, and no fault is reported. Protection means that the motor does not turn. The user thinks that there is a problem with the inverter, and it is required to replace a new one. Later, the replacement of the new machine still fails.
(2) Fault analysis: When the inverter is started by the forward button, the forward and reverse indicators of the inverter panel are on, which means that the inverter forward and reverse commands are enabled. It is no wonder that the motor Not running. This is strange, is it caused by interference!
(3) Troubleshooting: When adding magnetic ring to the main input and output of the inverter; replace all control lines with shielded wires; reduce the carrier frequency of the inverter. Through the above processing, the system returns to normal, which is really caused by interference.
5 Conclusions Above is part of the practical experience and experience of personal on-site debugging and troubleshooting. From the fault cases that occur in the inverter, most of them are related to the installation and operating conditions of the inverter. In particular, it is necessary to comply with the safety regulations. It is best to set the pv tube or copper, aluminum or iron pipe to protect the line and shield. . At the same time, after the fault occurs, first according to the fault phenomenon, the heart can have a preliminary diagnosis of the cause of the fault, or read the manual carefully or carefully check the wiring of the device.
In short, when encountering problems, don't worry, calm down and slowly check the cause. All faults are causal and can be solved satisfactorily.
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