Re: PFC?

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Bert Hickman by way of Terry Fritz <twftesla-at-qwest-dot-net>" <bert.hickman-at-aquila-dot-net>

Hi Dan,

Yes indeed, this is a true PFC. KVAR stands for Kilovolt Amperes
Reactive. This type of rating is often used to specify power factor
correction capacitors since it saves time converting from microfarads,
frequency, and operating voltage to what's really wanted: capacitive
reactance. It turns out that this particular capacitor is actually a
three phase metalized polypropylene PFC cap. What makes it a bit
confusing is that the cap has 5 quick disconnect terminals and what
appear to be bleeder resistors.  

Refer to the ASCII art drawing below. Two of the terminals (T1 and T3)
are for Loss of KVAR indicator lights  - leave these disconnected. The
remaining three terminals (T2, T4, and T5) are used to provide three
phase power factor correction. Internally, the capacitor has 3 equal
capacitors connected in a "delta" configuration. 

For single phase use, you can simply pick any pair of the three phase
terminals: 

               T4   | |   T5
                O---| |---O      
                |   | |   |
                |         |
              -----     -----
              -----     -----     
                |         |
        T1      |    T2   |       T3
         O      -----O-----        O

The cap is rated at 5 KVAR at 240 VAC and 60 Hz. The total capacitance
is made up of the sum of the three individual internal caps. You can
calculate their size as follows:

   Ctotal = 1000*KVAR/(2*Pi*F*(V^2)
 where:
     C = uF
     KVAR = KiloVolt-Amperes-Reactive rating
     F = 60 Hz
     V = line-to-line voltage (RMS)
 Solving:
   C (total) =  230.3 uF  total
 Each individual cap can now be found:
   C (individually) = 230.3/3 ~ 76.8 uF
 
Finally, if you connect any pair of the phase leads (T2, T4, and T5) to
your circuit, you'll have about 77 uF in parallel with 154 uF, for an
effective capacitance of ~115 uF at 240 VAC. 

Not bad for an 80 cent cap, is it?   :^)

Best regards,

-- Bert --     
-- 
Bert Hickman
Stoneridge Engineering
Email:    bert.hickman-at-aquila-dot-net
Web Site: http://www.teslamania-dot-com

Tesla list wrote:
> 
> Original poster: "Dan by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<toodamtall1-at-yahoo-dot-com>
> 
> Hi Folks,
> Is this a pfc cap? I don't understand what kvar means.
> I also assume a 240V rated cap can be used on a 120v
> line right?
> 
> This one's $.80 is that correct?
> 
> http://ww2.usamfg-dot-net/cgi-bin/onramp.exe?pgm=itemdet.bbx&id=86045&custnum=&p
> assword=
> 
> Thanks
> Dan--Ft. Lauderdale

-- 
Bert Hickman
Stoneridge Engineering
"Electromagically" (TM) Shrunken Coins!
http://www.teslamania-dot-com