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In the daily maintenance of the inverter, various problems such as poor peripheral parameter setting or mechanical failure are often encountered. If the inverter is faulty, how to determine which part of the problem, according to the Guangdong technical standard maintenance engineer told me the inverter repair test knowledge, I will sort it out, and now share it with everyone.
First, static testing
1, test rectifier circuit
Find the P and N terminals of the internal DC power supply of the inverter, adjust the multimeter to the resistance X10, the red bar to P, and the black bar to R, S, T, respectively, should have a resistance of about tens of ohms. And basically balanced. Instead, the black bar is connected to the P terminal, and the red bar is sequentially connected to R, S, and T, and has a resistance close to infinity. The red bar is connected to the N-end and the above steps are repeated. The same result should be obtained. If there are the following results, it can be determined that the circuit has an abnormality, A. The three-phase resistance is unbalanced, which can explain the rectifier bridge failure. B. When the red bar is connected to the P terminal, the resistance is infinite, and it can be concluded that the rectifier bridge is faulty or the starting resistor is faulty.
2, test the inverter circuit
The red bar is connected to the P-side black bar and connected to U, V, and W respectively. There should be a resistance of several tens of ohms, and the resistance values ​​of the phases are basically the same, and the inversion should be infinite. Connect the black bar to the N terminal. Repeat the above steps to get the same result. Otherwise, the inverter module can be determined to be faulty.
Second, dynamic testing
After the static test result is normal, the dynamic test can be performed, that is, the power test machine is powered on. The following points must be noted before and after power-on:
1. Before power-on, you must confirm whether the input voltage is wrong. If the 380V power supply is connected to the 220V inverter, there will be a bomber (fried capacitor, varistor, module, etc.).
2. Check if the sockets of the inverter are connected correctly. If there is any loose wire, the connection may be abnormal, which may cause the inverter to malfunction. In severe cases, the machine may explode.
3. After the power is turned on, the fault display content is detected and the fault and the cause are preliminarily determined.
4. If the fault is not displayed, first check whether the parameter is abnormal and return the parameter after no-load (no motor) to start the inverter and test the U, V, W three-phase output voltage value. If there is a phase loss, three-phase unbalance, etc., the module or the drive board is faulty.
5, in the case of normal output voltage (no phase loss, three-phase balance), load test. When testing, it is best to test at full load.
Third, fault judgment
1. The rectifier module is damaged.
Usually caused by grid voltage or internal short circuit. Replace the rectifier bridge with the internal short circuit removed. When dealing with faults on site, it is important to check the user's power grid conditions, such as grid voltage, and whether there are equipment such as welding machines that are polluting the power grid.
2, the inverter module is damaged
Generally caused by motor or cable damage and drive circuit failure. After repairing the drive circuit, the drive waveform is replaced and the module is replaced. After replacing the engine board in the field service, you must also check the motor and connecting cables. Run the frequency converter without any faults.
3, no display after power-on
Generally, the switching power supply is damaged or the pre-charging circuit is damaged, so that the DC circuit is not caused by the DC voltage. If the starting resistor is damaged, the panel may be damaged.
4. Overvoltage or undervoltage is displayed after power-on
Generally, due to input phase loss, the circuit is aging and the board is exposed to moisture. Find out its voltage detection circuit and detection points and replace the damaged device.
5. Overcurrent or ground short circuit after power-on
This is generally due to damage to the current sensing circuit. Such as Hall components, op amps, etc.
6, start to display over current
Usually caused by damage to the drive circuit or inverter module.
7. No-load output voltage shows overload or over-current after normal load
This kind of situation is generally caused by improper parameter setting or damage to the aging module of the drive circuit.
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