RE: Power Factor Correction

Terry: what you have to watch out for is the difference between a
"motor start" and a "Motor run" cap.
One is designed for short term use (during spin up)
the other is for 100% duty cycle.
Expect the Run caps to be much more expensive.

> -----Original Message-----
> From: Tesla List [mailto:tesla-at-pupman-dot-com]
> Sent: Wednesday, July 28, 1999 4:03 PM
> To: tesla-at-pupman-dot-com
> Subject: Power Factor Correction
> Original Poster: Terry Fritz <twftesla-at-uswest-dot-net>
> Hi All,
> 	I was playing with computer models all day today and got
> interested in
> power factor correction caps.  I found I can get my coil down to about 8.2
> amps RMS input by adding 140uF of capacitance across the neon input.  This
> will reduce the VA input from around 1550 to about 1000.  Digi-Key sells
> little 20uf AC caps for fairly cheap and using a bunch of these
> would allow
> for easy adjustment of the value.  Reducing the input current would take
> the load off the control box parts and let me run the coil and gap motor
> off the 15 amp power strip (the strip breaker likes to blow otherwise).  I
> did have a few questions for those that know about such things.
> I notice that same AC capacitors (like ones from GE) are
> significantly more
> expensive than others.  They are all full-time motor run caps made with
> polypropylene (I bet some or oil filled) but I was wondering why the price
> difference for what appears to be the same cap?  the 60UuF were
> $15 for one
> manufacturer and $65 for GE...  Digi-Key sells only 20uF but the price is
> faily good for the value I need even if I do need to use 7 of them...
> Are there any hidden things I should know about like inrush currents, cap
> explosions, openload or short problems?  I ran some models with various
> faults and all looked very good but...
> Is there any easy way to calculate the cap value for a real coil with all
> of it's dynamics?  MicroSim could easily find the value but I was
> wondering
> if there was an easy equation or something like that.  The value is not
> real critical.
> Cheers,
> 	Terry