Frequency converter harmonic induced system power failure analysis and processing - Database & Sql Blog Articles

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Due to the influence of the frequency characteristics of the circuit parameters, the inductance of the inductor under the action of the nth harmonic is, the capacitive reactance of the capacitor is the equivalent complex impedance of the entire power supply filter; where is the equivalent inductive reactance of the filter, which is the filtering The equivalent capacitive reactance of the device. If the value of the equivalent inductive reactance of the filter at the subharmonic is equal to the value of the equivalent capacitive reactance under the action of the kth harmonic, the equivalent complex impedance of the circuit at that frequency, that is, the circuit In resonance. Since R is only the line resistance at this time, its value is very small, and it can be approximated that the circuit is in a short-circuit state under the action of the subharmonic. According to the above analysis, it can be concluded that the short-circuit fault of the power supply is caused by the series resonance of the power supply filter due to the higher harmonic components of the inverter output. Under normal circumstances, if the harmonic component causing the resonance is not large enough, it should not cause a short-circuit fault, but when the effective value of the short-circuit current exceeds the protection range of the system fuse, it will cause a short-circuit fault. The way is not very suitable.

“This power supply short-circuit fault is caused by the series resonance of the power supply filter due to the higher harmonic components of the inverter output.”

1. "High-order harmonic components cause series resonance of the power supply filter" is a wrong statement!

2, "The short-circuit fault of the power supply is caused by the series resonance of the power supply filter caused by the high-order harmonic components of the inverter output" is even more wrong!

3. When series resonance, only the signal of the resonant frequency is short-circuited, and no resonance or short circuit occurs to other frequency signals;

4. The short-circuit of the power supply is the current of the power supply frequency. The power supply frequency is far away from the harmonic frequency. How can it be short-circuited?

5. As if you were listening to a radio broadcast, the resonance only occurred on the radio frequency signal you listened to;

6. It is as if you are listening to radio broadcasts, the resonance only occurs at the frequency of the station you are listening to. The signals of other stations are blocked and cannot be short-circuited!