RE: [TCML] PFC Question (again)

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

Let me see if I understand this.  You added a 700 uF PFC cap to the primary side of the unloaded PT.

I don't think this is surprising.  Since the PT is unloaded, it should present only a small reactive load, but the huge PFC cap presents a huge reactive load.  Maybe if the PT was capacitively loaded, driving a TC, it might cancel?  Can you tell that I'm talking just a little bit through my hat ;-) ?

Regards, Gary Lau
MA, USA

> -----Original Message-----
> From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
> Behalf Of David Rieben
> Sent: Tuesday, May 20, 2008 12:18 PM
> To: Tesla list
> Subject: [TCML] PFC Question (again)
>
> Hi all,
>
> I have already posted this question once about four days ago
> and as of yet I have not received a single response to it. I am
> going to try posting it once again and see if it blips on anyone's
> radar screen this time araound :^) ...............
>
>
>
> Hi all,
>
> I ran the specs of my medium PT powered coil through JavaTC
> and came up with something like 675 uFd for suggested PFC.
> I tied in (7) paralleled 100 uFd run caps in parallel with the
> main input to the PT and the saturable reactor ballast. The
> added 700 uFd actually caused the transformer/sat reactor
> to draw about 40 to 45 amps with 120 volts input before I
> even started gradually ramping up the voltage to the control
> coil of the sat. reactor. The only "real" load was the insigni-
> ficant SG cooling fan. Now what was really strange is that
> as I cranked the input voltage to the PT/sat. reactor (not
> the control voltage) to beyond about 140 volts, the current
> draw suddenly begun to DECREASE and if I kept increasing
> the voltage beyond this point, the coil would start to spit
> out sparks without any voltage into the sat. reactor's control
> coil. Normally, the PT cannot pass enough current to fire
> the coil when there is zero voltage to the control coil of the
> saturable reactor, even with 140 volts of input. Of course the
> abrupt sparking would cause the current to once again increase.
>
> Question - can anyone explain these effects and should I
> only parallel the PFC with the input of the PT only and not
> the main input to the PT and its ballast? Do PFCs really work
> for non-shunted transformers in SG driven Tesla coil circuits?
>
> The PT is a 120:1 (14,400 volt) 1.5 kVA @ 30*C GE instrument
> transformer and the saturable reactor is rated at 12 kVA and was
> originally paired with a 15 kVA, 240V/20 KV dry neon bombarder
> transformer (which I in fact still have ;^). Sorry but I don't really
> know the exact inductance ratings of the transformer or reactor.
> The secondary coil is wound with about 28" on a 6.5" OD PVC
> pipe with #22 AWG magnet wire. The primary C is .04 uFd driven
> through an air-cooled stationary SG and the topload is a 6 x 30"
> dryerduct donut.
>
> Thanks in advance for any advice,
> David R.
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