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Re: [TCML] PFC Question (again)



Hi Bart, David D,


Yes, Dave's little write-up did kind of open up my eyes
a bit on the subject, too.  It also reminded me that math
is not my strong suit ;^) and that you're not going to get
a full grasp of PFC theory from a 5 minute "skim over"
of the text ;^) I suppose that I should take the time to
actually "study" it but I must admit that since it has abso-
lutely nothing to do with my day job, I tend to be a bit
lazy about studying ;^o I also forgot to mention that
there was another inductor that I didn't consider in
my write-up. I started just hooking the input of my
PT to the output of the control panel for my large Green
Monster Tesla coil and keeping the voltage control variac
input voltage to <150 volts. That ballast was never consi-
dered either! Yea, I got tired of trying to keep her tamed
down to a 120 volt, 20 amp maximum circuit and the
much higher limit on input power sure makes for some
nicer sparks ;^)

Take care,
David

----- Original Message ----- From: "bartb" <bartb@xxxxxxxxxxxxxxxx>
To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
Sent: Friday, May 23, 2008 10:52 PM
Subject: Re: [TCML] PFC Question (again)


Hi David,

Thank you very much for this write up! Your link at the top of the page regarding PFC pretty much reflects what I learned in school (over 20 years ago). The memories are still there. However, I haven't worked with it on the job, so it's mostly a reminder (and a good one).

From" my view", if we are to benefit from PFC, it would be between gap conduction when the transformer is not shorted out. I also don't care about resonant cases, but I do care about STR and LTR operation as both are very common. For PT's and PIG's, STR operation is the norm. For NST's and the like, LTR is common. For an NST using PFC, then the option of placement is limited across the input to the transformer. For PT's and PIG's, it is common to current limit inductively and to PFC before the transformer after the ballast. It seems correct to me to connect the PFC across the transformer after the limiting is occurring before the PIG or PT. Thus, for those transformer types, we have the transformer and tank cap to work with in the PFC scheme.

I personally don't use PFC on any coils. Javatc simply gives a basic PFC ballpark number based solely on the transformer. If one was to use PFC's, they would at least have a capacitive range in the vicinity (although their mileage will vary with input, transformer, and tank cap). I think considering the common transformer sizes used and coil dictated cap sizes, PFC's may be a help, but I've never had the need.

I've thought about this PFC value in the past with this exact scenario. I've contemplated simply removing the output from Javatc (heck, I don't use it). But some have found it handy, and so I've kept it in the program.

Javatc has born an interesting scenario that I am privy to (and no one else is on the TCML). For example, if I take only 2 coilers and have them decide what they use and don't use, etc. I will get very different answers. But when you compound that with 100 coilers over the years, you get amazingly different points of view of what they want in a program. Some things you can do well, other things are iffy. PFC is one of those iffy things. There's no way to make everyone happy, so every output requested by coilers becomes a judgment call of which I am ultimately responsible for. I get ridiculed every week for something, but I also have the past request from other coilers that helps me balance out the ridicule.

Only those who have tried to program Tesla Coil info can relate. Those who haven't written and had coilers use it are arm chair cowboys at best. They are experts at finding an error and inflating it into mega proportions. Two years ago, I was begging for someone else to write a program for coilers (I was just bogged down with personal opinions), but no one did. I even emailed my core code to a couple prospects who were going to take it and write something great for all of us. Nothing came of it. So here I am today still defending the program. I don't defend the PFC thing however as it is simply a ballpark value and experimentation will tell the tale.

I wonder if users would rather not have PFC listed? Deleting stuff is easy. I have no problem getting rid of it.

Take care,
Bart

David Dean wrote:
Hi

See:

http://deanostoybox.com/pfc.html

for some of my thoughts on the subject.

later

On Thursday 22 May 2008 07:55:38 am David Dean wrote:

Hi Bart

I do not mean to leave you hanging, but after giving much thought, have
found myself unable to express my opinions on the subject in just a few
words. A few pictures perhaps. May take some time. Will advise when I have
something presentable.

later

deano



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