1. Overpressure leads to brake pipe breakdown.
The so-called overvoltage of the inverter refers to the inverter voltage formed due to various reasons that 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 no problems were found 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 parking.
Conclusion: Inverter overvoltage is one of the factors that lead to inverter breakdown.
2. Excessive surge voltage leads to insulation breakdown.
Cause: A surge voltage occurs when the resonance of the dispersive capacitance and dispersive 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: Select a motor with high dielectric strength plus an AC output reactor (impedance of 3%) plus an output inductance L, capacitance C, and 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 large reduction of the load at the output will constitute a huge reverse electromotive force, which will have an effect on the inverter, and when the electromotive force is large enough, it will lead to the breakdown of the module and even the formation of an explosion.
For example, if the load is suddenly disconnected during the normal operation of the inverter, the motor with a large inductance will have a self-induced electromotive force, and it will be superimposed in the same direction as the power supply voltage (the voltage output by the inverter) to form a high voltage, and the voltage at both ends of the IGBT will have a small effect, 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 to maintain 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 during the inspection, and the input phase loss detection plate was severely burned out. The inverter part and the other parts are normal.
Speculation is that the input varistor is not broken, and it is clear that the power supply is a problem caused by the impact caused by excessive current.
In addition to the above four conditions, we will also encounter many problems about the breakdown of the inverter (for example: the breakdown of the inverter CPU) in daily use, in addition to the reasons listed above, there are also external inducements such as environmental humidity and metal dust that cause the breakdown of the inverter, and these problems need to be further considered.
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