【Daily Question 20090227】Is it feasible to wire the inverter in this way (II)?
Thread Content
【Daily Question 20090227】Some facilities, in order to further improve the power factor of motors driven by high-power frequency converters, connect reactive power compensation capacitors in parallel with the motors. This wiring method is not appropriate; but what about connecting capacitors on the power supply side of the frequency converter? Is that acceptable? Can it improve the power factor?
The widespread use of frequency converters is the direct cause of overcurrent/overheating problems in low-voltage compensation capacitors… The allowable overcurrent level for ordinary capacitors is 1.3 times their rated current. When the harmonic components generated by frequency converters exceed this limit, the resulting faults include the capacitor overheating and swelling, fuses blowing, overheating of the connection terminals, and the protection relay activating as a result of which the capacitor cannot be used. Additionally, the average power factor also decreases. .
It is explicitly prohibited to connect capacitors in parallel on the output side of the frequency converter
There is no problem with connecting capacitors on the input side, as there are multiple power distribution devices on the low-voltage bus; it’s not possible to shut down all of them just because a frequency converter with reactive power compensation is installed. However, frequency converters tend to generate high-order harmonics that can affect the capacitors, and in our company’s reactive power compensation cabinets, capacitor explosions have indeed occurred. Measures to eliminate higher harmonics should be taken.
It’s not necessary, but it’s fine to add them anyway. There’s no difference between capacitors placed on the power supply side and those on the busbars; however, as in the question from yesterday, it’s prohibited to place them on the output side.
When there are reactive power compensation capacitors or thyristor-controlled phase-shifted loads on the same power supply node that feeds the inverter, the reactive power transients caused by the switching of these capacitors can lead to sudden changes in grid voltage, while the harmonics generated by the phase-shifted loads may cause damage to the input rectifier circuit of the inverter. If such a situation occurs, a DC reactor can be configured for the inverter to resolve it.
Loading from the output side is not allowed. Otherwise, it may cause damage to the capacitor. Measures to eliminate higher harmonics should be taken.
Sure, but power factor compensation is usually done in the substation! Why are you measuring the inverter input? ? It’s It’s inexplicable!