NST question-Why a Tap?

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Original poster: "S.Gaeta" <sgtporky-at-prodigy-dot-net> 

Hi All,

I have a bit of a mystery here. I recently depotted a Jefferson Electric
12/60 NST.
I found a pfc cap inside. It is 4 uF at 660V. I found that the primary has
three connections. The AC line is connected across the 55 mHy section, and
the pfc cap goes across the entire winding. The extra winding measures 1.24
Henries. Expressed another way, the cap is in series with an inductor that
is much larger than the primary inductance, and this LC circuit is in
parallel with the primary.

Ok I just did the math and found that the LC circuit comes out to 71 Hz. OK
so my math or measurements or both is a little bit off, but this LC network
is intended to be resonant at 60 Hz (close enough).

So what is the purpose of this LC cicuit?
I thought that all that was required for pfc is a cap across the line, and
primary.

Thanks,
Sue