Why tune to the 5th harmonic?
A. The 5th harmonic is generally considered to be the most offending. It is important that the tuned frequency for the 5th harmonic be at least at the 4.2nd harmonic. Tuning slightly below the offending harmonic will accommodate for standard tolerances in the manufacturing process, but remove the largest offending portion of the 5th harmonic. Parallel resonance will occur around the 4th harmonic, at a much lower amplitude and in an area that does no harm to the capacitors or system. Many other systems are designed at the 3.78th harmonic to help extend the life of the capacitors. This tuning frequency does not remove the majority of the 5th, 7th, etc. harmonic from the system.
