In the routine maintenance of the frequency converter, a variety of problems are often encountered, such as peripheral circuit problems, poor parameter settings, or mechanical faults. It is also possible that the inverter has malfunctioned. If the inverter is faulty, how to determine which part is the problem is briefly introduced here.
A static test
1. Test rectifier circuit
Find the P terminal and N terminal of the internal DC power supply of the inverter, find Ten Thousand Meters to adjust the resistance to the X10 file, the red bar to P, the black bar to R, S, and T, respectively. There should be approximately tens of Euros of resistance. And basically balanced. Instead, the black bar is connected to the P terminal. The red bar receives R, S, and T in turn and has a resistance close to infinity. Bring the red stick to the N-side and repeat the above steps to achieve the same result. If there are the following results, it can be determined that the circuit has abnormal, 1 three-phase unbalanced resistance, it can explain rectifier bridge failure. 2 When the red bar is connected to the P terminal, the resistance is infinite, and it can be determined that the rectifier bridge fault or starting resistor is faulty.
2. Test inverter circuit
The red bar is connected to the P terminal. The black bar is connected to U, V, W, respectively. There should be several tens of euros of resistance, and the phase resistance is basically the same, but the opposite should be infinite. Connect the black meter to the N terminal and repeat the above steps to obtain the same result. Otherwise, you can determine the failure of the inverter module.
Second, dynamic testing
After the static test result is normal, the dynamic test can be performed, that is, the power on test machine. The following points must be observed before and after power-on.
1. Before powering on, make sure whether the input voltage is incorrect or not. If the 380V power supply is connected to a 220V inverter, there will be explosions (fried capacitors, varistors, modules, etc.).
2. Check whether the frequency converter's access ports are properly connected and whether the connection is loose. Sometimes the connection may be abnormal, which may cause the inverter to malfunction. In severe cases, it may cause explosives.
3. Detect the fault display content after power-on, and preliminarily determine the cause of the fault.
4. If the fault is not displayed, first check whether the parameters are abnormal, and reset the parameters, start the inverter with no load (motor not connected), and test the U, V, W three-phase output voltage values. If there is a missing phase, the three-phase output voltage value. If there is a lack of phase, three-phase imbalance, etc., the module or the driver board is faulty.
5. With the output voltage normal (no missing phase, three phase unbalanced), load test. When testing, it is best to use a full load test.
Third, fault diagnosis
1, the rectifier module is damaged
It is usually caused by the voltage of the secondary grid or an internal short circuit. Replace the rectifier bridge if the internal short circuit is eliminated. When dealing with faults at the site, it is important to check the user's power grid conditions, such as grid voltage, presence of equipment such as welders that are contaminated by the power grid, and so on.
2. Inverter module is damaged
It is generally caused by damage to the motor or cable and drive failure. After repairing the driver circuit, replace the module with a good drive waveform. After replacing the drive plate in the field service, you must also pay attention to check the motor and connecting cable. Run the inverter without any problem.
3, no display on power
Generally, due to damage of the switching power supply or damage of the soft charging circuit, the DC circuit may not be caused by direct current. If the starting resistor is damaged, the panel may be damaged.
4, after power on or over voltage
Generally due to the lack of input phase, aging of the circuit and moisture in the circuit board. Find out its voltage detection circuit and detection point and replace the damaged device.
5, display current or ground short circuit after power on
It is generally damaged in the current detection circuit. Such as Hall elements, op amps and so on.
6, start to show over-current
Generally caused by damage to the drive circuit or reverse flow module.
7, no-load output voltage is normal, with overload display or over-current
This situation is generally due to improper parameter settings or aging of the drive circuit, causing damage to the module.
Keywords in this article: Zhuzhou inverter, inverter maintenance, inverter control cabinet
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