If the inverter fails, how to analyze and deal with the problem, I will introduce a little bit in the practice.
First, through the static test to determine the fault General general-purpose inverter generally includes the following parts (1) rectifier circuit; (2) DC intermediate circuit; (3) inverter circuit; (4) control circuit. The static test is mainly a test of the high-power transistor (power module) of the rectifier circuit, the DC intermediate circuit and the inverter circuit part. The rectifier circuit mainly tests a forward and reverse of the rectifier diode to judge whether it is good or bad. The DC intermediate circuit is mainly for measuring the capacity and withstand voltage of the filter capacitor. We can also observe whether the safety valve on the capacitor is popped open, whether there is leakage or not, to judge whether it is good or bad. The quality of the power module is judged mainly by the judgment of the freewheeling diode in the power module. For the IGBT module, we also need to judge whether it can be turned on and off in the presence of a trigger voltage.
1. Test the rectifier circuit to find the P terminal and N terminal of the internal DC power supply of the inverter, adjust the multimeter to the resistance X10 file, the red watch bar is connected to P, and the black watch bar is respectively connected to R, S, T, which should have about tens 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.
Rectifier module damage is generally caused by grid voltage or internal short circuits. 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. Test the inverter circuit to connect the red bar to the P terminal. 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 can be determined. At this time, you cannot blindly power on, especially if the rectifier bridge is damaged or there is obvious burning damage on the circuit board, especially the power-on is prohibited, so as to avoid further loss.
Inverter module damage is 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.
Second, through the dynamic test to determine the fault If the static measurement results show that the module is basically no problem, you can power on the observation, through the display of the inverter after power-on, preliminary determination of the fault and the cause.
1. There is no display on the rear panel after power-on. This situation is generally caused by damage to the switching power supply or damage to the soft charging circuit, so that the DC circuit is not caused by DC power. If the starting resistor is damaged, the panel may be damaged.
2. The panel does not show a fault after power-on. In this case, 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 lack of phase, three-phase unbalance, etc., the module or the drive board is faulty; in the case of normal output voltage (no phase loss, three-phase balance), the load test. When testing, it is best to test at full load.
3. OC. Overcurrent fault. (1) The overcurrent or ground short circuit after power-on is generally caused by damage of the current detection circuit, such as Hall element, op amp, etc.; (2) The overcurrent fault is usually caused by damage to the drive circuit or inverter module. (3) The no-load output voltage is normal, and the overload or over-current is displayed after loading. This kind of situation is generally caused by improper parameter setting or aging of the drive circuit. This may be the most common fault in the inverter caused by module damage. We must first rule out the fault caused by the parameter problem. For example, current limitation, too short acceleration time may lead to overcurrent. Then we have to judge whether the current detection circuit is faulty. Take the FVR075G7S-4EX as an example: We sometimes see that the panel also has a current display when the motor is not connected. Where does the current come from? At this time, we must test its three Hall sensors. In order to determine the damage of the phase sensor, we can open the machine every time the sensor is removed. (Original source: http://) Whether there will be an overcurrent display, after this test can basically eliminate the OC fault.
4.OV. Overvoltage fault. After the power is turned on, the overvoltage is generally caused by the input phase loss, the aging of the circuit, and the moisture of the board. Find out its voltage detection circuit and detection points and replace the damaged device. We must first rule out the fault caused by the parameter problem. For example, the deceleration time is too short, and the overvoltage caused by the regenerative load, etc., then we can look at whether there is a problem with the input side voltage. Finally, we can look at whether the voltage detection circuit has a fault, the voltage sampling of the general voltage detection circuit. Points are the voltages of the intermediate DC link. Let's take Sanken SVF303 as an example. It is sampled by DC loop (DC of about 530V) and is stepped down by a large resistor. It is isolated by optocoupler. When the voltage exceeds a certain value, it shows “5†overvoltage ( This machine is a digital tube display.) We can see if the resistance is oxidized and the optocoupler has a short circuit.
5.UV. Undervoltage fault. In this case, you can first look at whether there is a problem with the input side voltage. Then look at the voltage detection circuit. The fault judgment and overvoltage are the same.
6. FU. Fast fuse failure. Most of the currently available inverters have introduced the fast-fuse fault detection function (especially the high-power inverter). Taking LG030IH-4 inverter as an example, it mainly samples and detects the voltage behind the fast-melting front. When the fast-melting damage is inevitable, there will be no voltage at the fast-melting end. At this time, the isolated optocoupler is activated and a FU alarm occurs. Replacing fast melt can solve the problem. In particular, it should be noted that it is necessary to judge whether there is a problem with the main circuit before replacing the fast melt.
7. OH. Overheating fault. This situation is mainly caused by the poor internal heat dissipation of the inverter. The cooling fan and ventilation channel can be checked.
8.SC. Short circuit fault. In this case, it is possible to detect whether there is a short circuit inside the inverter. Taking Siemens 6SE7018 as an example, we can detect the internal circuit, and there may not be a short circuit. At this time, we can detect that the power module may have a fault. When the drive circuit is normal, replace the power module and it should be able to repair the machine.
There are many kinds of faults in the inverter, because some low-end simple original device problems and assembly problems lead to more failures. If there are drawings and parts, these problems are not difficult to solve and the cost is not high, otherwise it is not easy to solve these problems. The easiest way is to change the entire circuit board! We can only sum up in practice and find a way to deal with the fault of the inverter quickly and effectively.
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