First, static testing
1. Test the rectifier circuit to find the P and N terminals of the internal DC power supply of the inverter, adjust the multimeter to the resistance X10 file, the red bar to the P, and the black bar to the R, S, T, respectively. The resistance of Europe is 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 Connect the red bar to the P terminal, and the black bar is connected to U, V, and W respectively. There should be several ohms of resistance, 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 fault string 9 can be determined.
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 connection ports of the inverter are connected correctly, and if the connection is loose, the connection may be abnormal, which may cause the inverter to malfunction. In severe cases, a bomber may occur.
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 after resetting the parameter, start the inverter under no-load (no motor), and test the U, V, W three-phase output voltage value. If there is a phase loss or a three-phase unbalance, 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 due to the 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. Inverter module damage 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 pay attention to check the motor and the string 1 cable. Run the frequency converter without any faults.
3, no display after power-on Generally, the switching power supply is damaged or the soft charging circuit is damaged, so that the DC circuit is not caused by DC power. If the starting resistance 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 damp. Find out its voltage detection circuit and detection points and replace the damaged device.
5. Overcurrent or ground short circuit after power-on is generally caused by damage to the current detection circuit. Such as Hall components, op amps, etc.
6, start display over current is generally caused by damage to the drive circuit or inverter module.
7. The no-load output voltage is normal, and the overload or over-current is displayed after the load. This kind of situation is generally caused by improper parameter setting or aging of the drive circuit and module damage.
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