On Tue, Jul 15, 2008 at 5:58 PM, Lau, Gary <Gary.Lau@xxxxxx> wrote:
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
The transformer is a 15/30 with shunts removed. I'm running the PFC caps in
series with the 277V line. Running smaller capacitances than 30uf yields a
lower current drawn on the 120V side of the variac. Running 40uF or above
results in a higher current being drawn from the 120V side of the variac.
In addition to this the short circuit current of the NST increases. Maybe
I'm wiring the caps incorrectly? I know for a fact that the amount of
current in the secondary increased to a very high level causing the asphalt
to be melted. I was running the jacobs ladder at the time and it became
notably louder. Several seconds later asphalt started bubbling up out of
the oil.
Schematic ... sort of.
120V ------------ Variac ------------ ~277V -------- PFC -------
|
NST
|
Neutral
-----------------------------------------------------------------------
-----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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