Hello, I am doing well and thanks for asking.
A filter is required when power factor correction capacitors create a parallel resonance with the source inductance of the electrical system. The filter sets the tuning frequency to something below the 5th harmonic usually.
There are other alternatives you can try before jumping to a filter reactor. You can change to the capacitor size or the switching steps to avoid the resonant frequency. Or you can mitigate the harmonics at the load causing the harmonic current to flow.
As far as determing the proper size of the reactor for a new system, I believe the source inductance will have to be calculated/modeled. Then you can choose the appropriate capacitor sizes. If this is an existing system, then you should already know the harmonic frequency that is resonating. You should also know the capacitor bank size. From this information, you can calculate the system inductance from the following formula:
w = 1/(L*C)^.5
w - resonant frequency
L - system inductance
C - cap bank size
Adding in a tuning reactor will alter the L in the above equation to the point where "w" will be at the proper frequency, which is somewhere below the 5th harmonic.
The higher voltage rating is recommended because detuning the cap bank will increase the voltage across it due to increased current flow.
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