RE: [TCML] Power Factor Correction

["Lau, Gary" <Gary.Lau@xxxxxx>]

Hi Phillip,

30uF for a 15/120 NST sounds low by at least a factor of 10.  Was this determined using a Jacobs ladder for a load?  I don't think that represents a correct load for determining PFC caps.

Having the wrong PFC cap value cannot affect the current through the NST primary, or be responsible for the bubbling asphalt you cited.  You're applying the same 120VAC to the primary winding, and the primary has no awareness of the presence of a PFC cap.  Having too large a PFC cap CAN cause too much current being drawn from the wall socket, but the excess current would be going through the PFC cap, and it would be reactive current, so nothing gets hot except the wiring.

Regards, Gary Lau
MA, USA



> -----Original Message-----
> From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
> Behalf Of Phillip Slawinski
> Sent: Tuesday, July 15, 2008 4:59 PM
> To: Tesla Coil Mailing List
> Subject: Re: [TCML] Power Factor Correction
>
> As it turns out I only needed 30 uF of capacitance.
>
> On Tue, Jul 15, 2008 at 12:40 PM, Phillip Slawinski <pslawinski@xxxxxxxxx>
> wrote:
>
> > How do I know what direction to go with capacitance?  I'm running the NST
> > with my Jacobs ladder to find the right value.  So far I've only found the
> > wrong value, and the very wrong value.  Turns out if you get it wrong you
> > actually increase [dramatically] the amount of current being dumped into the
> > NST.  I was running it and all the sudden the aspahlt I neglected to remove
> > between the core and the HV windings bubbled up from the oil.  When I run
> > without the PFC caps I'm drawing about 15A, with the caps I was pulling peak
> > currents of 35A!  If I'm increasing current does that mean my capacitance is
> > too high or too low?
> >
> >
> > On Mon, Jul 14, 2008 at 11:58 PM, bartb <bartb@xxxxxxxxxxxxxxxx> wrote:
> >
> >> Javatc is giving a basic calculation for PFC based on the transformers
> >> specs. This is only a ball park number. You must experiment to find the PFC
> >> that works best for your coil. Does you coil have a variac control, external
> >> current limiting, etc.. etc.. Experiment is the only way to find the "good"
> >> value for your coil.
> >>
> >> Take care,
> >> Bart
> >>
> >> Phillip Slawinski wrote:
> >>
> >>> I just scored 20 GE Dielektrol VI caps 10uF at 370V AC @ $0.10/piece.
> >>>  These
> >>> should be good for PF caps.  I'm wondering what size PFC cap I should use
> >>> for a 15/120 NST.  I've noticed that the value suggested in JavaTC for a
> >>> 15/60 seems to be twice that of what others [notably Gary Lau] use.
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