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Re: Auto PFC? (And conclusion of Ballast Inductor) (And finishedsecondary)

Great idea... What you really need to do is measure the power factor,
though, rather than the current.  This is actually quite easy.  take the
supply voltage and turn it into a square wave.  Then take the current and
turn it into a square wave too (one of those $20 hall effect current
sensors is probably the easiest way.. or a toroidal core and a few turns of
wire to make a current transformer).  Rig up a little program that watches
the zero crossings (there will be noise, so it's not entirely trivial), and
adjust the caps to make the zero crossings occurr simultaneously.

For that matter, if you've got a micro processor there, you could probably
rig up something to display power and such in real time.

> From: Tesla list <tesla-at-pupman-dot-com>
> To: tesla-at-pupman-dot-com
> Subject: Auto PFC?  (And conclusion of Ballast Inductor) (And
> Date: Monday, October 09, 2000 5:20 PM
> Original poster: "M Fabs" <the_machin_shin-at-hotmail-dot-com> 
> I was wondering about automatic PFC.  I have a whole bunch of PFC caps, 
> triacs, and zero-crossing-triac-out optocouplers.  Can I montitor the
> current with a simple microcontroller, then tell that when to switch caps

> into and out of the circuit?  Would triacs be happy switching caps onto
> line at zero crossings?  Any thoughts on this hair brained scheme would
> welcomed.
> I was thinking that I would average the rms current over several cycles 
> before deciding to make a cap switch. I was also thinking of arranging
> caps this way ...x*8, x*4, x*2, x*1, x*1/2... where x in my case is 15uF.
> can just use a binary up/down counter to keep track of which total cap
> I am at and to signal the optocouplers.  In the microcontroller I would 
> probably just keep track of the last two switches to find out if I have 
> reached a minimum...
> About my ballast inductor (woefully underwound, and undersized), I have 
> decided to wait indefinitely on that for any further modifications; I
> probably just get a variac :)
> (Max inductance != Max current)
> Thanks for alllll the help!
> I finished my secondary coil, I am pleased with how it looks.  4" SCH 40
> wound for x" with #22 wire.  I will measure it tonight, and measure it's 
> inductance tomorrow.  The final poly coat is still drying. Bearings and 
> threaded rod are your friends. (Motors help too...)
> Pleased to say it is all coming together.  It's only been 2 years...
> Michael.
> I apologize if this message showed up twice....
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