Capacitive Ballasting

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

Original poster: "Alfred Erpel by way of Terry Fritz <twftesla-at-qwest-dot-net>" <alfred-at-erpel-dot-com>


Howdy all,

 I was wondering about the merits of capacitive ballasting a transformer
with electrolytic photo capacitors since you can get them for free from
disposable cameras and they have high enough capacitance in a small enough
footprint to be practical.

ASCII art warning -- make sure you have on a fixed width font. I use Courier
New.



                   electrolytic
         diodes     capacitors
   -------->|--------|+ -|-------------o  o-----
  |     |                   |          o||o
  |     |                   |          o||o
  |      --|<--------|+ -|--           o||o
  |                                    o||o
|A C|                                  o||o Xformer
  |                                    o||o
  |      -->|--------|+ -|--           o||o
  |     |                   |          o||o
  |     |                   |          o||o
   --------|<--------|+ -|-------------o  o------
                   electrolytic
         diodes     capacitors


Would the above circuit have any problems? Is this a stress for a good
electrolytic?
X(c) = 1 / (2*pi*f*capacitance)
At .000160 F and f=60 Hz, a typical photo electrolytic yields a reactance of
16.578 ohms. Putting 4 in series would yield 66.315 ohms which would limit
115 volts to 1.734 amps. I know one thing to worry about would be that you
aren't around resonance with the transformer's primary. How would each leg
of the circuit "see" the capacitance? For instance, if the circuit above
just had four 160 uF capacitors (one for each diode), for calculating
reactance would you use 80 uF in the reactance equation or 320 uF? Would it
even work?

Regards,

Al Erpel