Re: Capacitive Ballasting

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

Original poster: "Darren Freeman by way of Terry Fritz <twftesla-at-qwest-dot-net>" <free0076-at-flinders.edu.au>

At 04:26 PM 25/02/2002, you wrote:
>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.

I think you'd find that they have high losses and explode when passing that 
kind of current =)

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

Yeah! ASCII art rocks!



>                    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?

The diodes would rectify the current, charge the caps and the circuit would 
stop sending power to the coil.

>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?

Please don't try this in case they DO explode... It won't work anyway.

>Regards,
>
>Al Erpel


Have fun,
Darren Freeman