1. Overpressure leads to brake pipe breakdown.
The so-called overvoltage of the inverter refers to the fact that the inverter voltage composed of various reasons exceeds the rated voltage, which is reflected in the DC voltage of the inverter DC bus.
The overvoltage alarm generally appears at the time of shutdown, and the main reason is that the deceleration time is too short or there is a problem with the braking resistance and braking unit.
Example: A Taian N2 series 3.7kW inverter jumps "OU" when it is stopped.
Condition: When repairing this machine, we focused on checking the braking circuit, and there was no problem in the discharge resistance measurement. However, when measuring the brake pipe (ET191), it was found that it had broken down, and after replacement, it was powered on and running, and there was no problem with fast stopping.
Conclusion: Inverter overvoltage is one of the factors that cause inverter breakdown.
2. Excessive surge voltage leads to insulation breakdown.
Cause: A surge voltage occurs when the resonance of the distributed capacitance and distributed inductance on the output line is superimposed on the output voltage. The higher the switching frequency of transistors and IGBTs, the longer the wiring, the higher the surge voltage, and at the maximum, the surge voltage can be twice the DC voltage.
Solution: Adopt a motor with high dielectric strength plus an AC output reactor (impedance of 3%) plus an output inductor L, capacitance C, resistance R filter.
3. The load of the inverter is suddenly disconnected, resulting in the breakdown of the module.
Reason: A contactor is installed at the output end of the inverter
Principle: During the normal operation of the inverter, the sudden and substantial reduction of the load at the output will constitute a large reverse electromotive force, which will act on the inverter, and when the electromotive force is large enough, it will lead to breakdown of the module and even constitute a blast.
For example, when the load is suddenly disconnected during the normal operation of the inverter, the motor with large inductance will have self-induced electromotive force, and the power supply voltage (the voltage output by the inverter) will be superimposed in the same direction to form a high voltage, which has a small effect on the voltage of the two ends of the IGBT that is turned on, but it will constitute an overvoltage at the two ends of the IGBT in the reverse cut-off, and if the voltage is large enough, it will break down the IGBT.
Solution: Do not install a contactor at the output end of the inverter, and keep the load of the inverter so that it does not suddenly drop the load.
Fourth, three-phase rectification full breakdown
Case: A customer repaired the inverter, and found that the three-phase rectifier broke down when he checked it, and by the way, he entered the phase loss detection board and burned out severely. The inverter part and the other parts are normal.
Speculation is that the input varistor is not broken, and it is clear that it is a problem with the power supply, and the current is too large and causes the shock to burn out.
In addition to the above four conditions, we will also encounter a lot of problems about inverter breakdown (such as: inverter CPU breakdown) in daily use, in addition to the above listed reasons, there are also external inducements such as environmental humidity, metal dust and other external inducements that lead to inverter breakdown, and these problems need to be further considered.
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