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Re: [TCML] PFC reflection back to current control.


On Thursday 02 April 2009 08:44:38 pm bartb wrote:
> Maybe some check boxes for NST, OBIT, PIG, PT, MOT, etc. would help
> define the transformer. A requirement for externally ballasted
> transformers would be a current limit value. Some defining
> implementation of the above may help get nearer to the ball park, but
> there are still many issues that require experimentation regardless with
> PFC.

How true.

And then we do all these calculations as if there actually were an "infinite 
buss", never taking into account source impedance. For the typical pig coiler 
with a 10-15KVA pig powered coil with some type of inductive ballast setup -- 
first there is the variac, then the line filter, then the 40-50 feet of #6 or 
#8 SO cord or romex to get from the back wall of the garage where the panel is 
out to the middle of the driveway. Then there is the 200A service fed by 
150-200 feet (or more) of #000 URD, then that 25-75KVA pad mount with 2-8% 
impedance shared with 3-5 other houses. And on and on all the way back to the 

Then there are all the other things that can mess with the power factor, like 
the rotary spark gap motor, or the vacuum motor for the sucker gap, or the air 
compressor for the blast gap. Or the next door neighbors air conditioner, or 
the big factory down the road.

Yes, power factor can be a big can of worms. It may look like a little can of 
spaghetti at first glance, but when you open that thing up you find a great big 
can of worms.

I think the best way to determine what you need for power factor correction is 
to set up an oscilloscope with a current transformer so you can see the phase 
relationship between E and I, then add a little bit of capacitance at a time 
until you find the best fit. And keep in mind that if you change anything like 
input voltage, ballast setting, breakrate, or tank cap, it is all out the 
window and back to the drawing board.

Here are a couple of pictures from back in 2002 from the Hot-Streamer archives:


and the folder they are in:


in case you want to get the time stamps off the files and search the pupman mail 
archives for that time frame and subject.

Oh, and while I was looking for something else, I found this. Lots of pictures 
on my web site that have never been hooked up to a page, this one is of a jury 
rigged contraption I used to find the right size capacitor for my "John Freau 
Phase Shifter" for my SRSG. It does 0-75uF in 5uF steps. 
Or for those who do the webmail thing, in case you get a 403 error:

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