Re: Power Factor Correction weirdness?

• To: tesla-at-pupman-dot-com
• Subject: Re: Power Factor Correction weirdness?
• From: Ed Phillips <evp-at-pacbell-dot-net> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)
• Date: Wed, 09 Feb 2000 18:46:46 -0700
• Approved: twftesla-at-uswest-dot-net
• Delivered-To: fixup-tesla-at-pupman-dot-com-at-fixme

Tesla List wrote:
> 
> Original Poster: Adam <adamsmith-at-mediaone-dot-net>
> 
> Can someone explain what I'm seeing when I attempt to power factor correct
> my neons? I've got my DMM in series with the primary of a 12,000 60mA NST,
> and the secondary of the NST is shorted.  With no PFC caps, it reads 7.13
> Amps.  But when I start adding caps in parallel with the NST primary, the
> current reading drops dramatically-- more than I expected it to.  Here are
> the results:
> 
>     PFC Caps    Ammeter Reading (amps)
> 
>     0                7.13
>     50 uF            4.96
>     100 uF           2.81
>     150 uF           1.14
> 
> What's going on here? is this right?
> 
> -Adam
> adamsmith-at-mediaone-dot-net

	Sounds about right!  My simple calculation says the optimum capacitance
should be a bit over 100 ufd.  Remember, under short-circuit conditions
you're drawing almost no power and the primary current is due to the
transformed inductive leakage reactance; the purpose of the PFC is to
supply that current, instead of it coming from the power line.

Ed

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