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Re: [TCML] PFC Question (again)

Hi David,
I still have your original message. It was on the "to do" list. I lost Comcast for a couple days and now I'm playing catch up.
Before I start, let me tell you I don't use PFC caps at all. The effects your seeing I can only theorize from an arm chair cowboy stance. One thing I noticed is that your PFC is not tied directly across the PT inputs. The value listed (which is a ballpark number) is meant for connecting the PFC directly across the low voltage input to the transformer. I'm not exactly sure of your connection (PT and ballast). It may make little difference, but I at least wanted to state the intent of connection.
The PFC is there to correct the power factor for the transformers ratings. The additional L in the ballast will affect this as will the inductive load of the Tesla Coil. Note that as you increase voltage, the current drops and with little ballast the coil wants to fire. This is a clear sine of the PFC doing it's job. With the ballast at zero and no minimal voltage, the PFC is capacitively large. As you begin increasing voltage, the inductance begins to cancel out this reactive current and should ideally be minimum at full voltage.
This may be normal observation as to how your powering up the coil. I guess it would help if "those" that use PFC's could enlighten the rest of us on their experience, values, situation, etc...
I'm not a lot of help here. I was hoping that someone who used PFC's would have given some experience and details. With the basic PFC equation, I've had no feedback on PFC usage. 

Take care,
Bart



David Rieben wrote:

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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