Pulse charging capacitors

[turniton]

Polarization...

Therefor my thinking is that a large surface area (flat plates), with small capacitance would be better for pulse charging, and could easily be put in parallel with more of the same, reducing the incoming resistances/reluctance.

awaiting thoughts on this...

[Yucca]

Hi Turniton,

Interesting subject, my thoughts are this.

You´re right, for effectively mopping up fast transients you want caps with a very low equivalent series resistance (ESR) and also a high voltage rating.

Coil generated transients tend to consist of a very sharp front which goes very highV for a very short time followed by the main exponential body of the pulse which is much lower V and lasts alot longer time.

Maybe we don´t need all of our C to be low ESR, but just enough to catch that fast front.

So perhaps a good way is to build a capacitor cascade using a few different caps in parallel:

Use ultra low ESR caps as close as poss to the pulse source. You can use fairly small C here because it only needs to do its job for a very small time. You want it to be high V though.

Then parallel behind that use a slightly higher ESR of a slightly larger C with a slightly lower V

You can carry on and end up with some big cheap electrolytics with quite high ESR and fairly low V at the back.

The parallel bus wires should probably be made out of nice thick wire or maybe even better would be nice wide copper strips like wide copper tape that in itself can form an ultra low ESR and high V cap by facing the copper plates together with an airgap.

Whether some cascaded inductors would be needed in series with the caps I´m not sure at the moment

Obviously the above is just an idea, I am defo going to get hold ofsome RF doorknob caps as TK suggests for catching fast transients and then maybe play with the above idea.

[jadaro2600]

displacement current
[image]

Reminds me of the contrarotating homopolar disk setup...as in a capacitive homopolar motor.

I've very new to electronics, is there a way to charge a capacitor without it discharging back trhough the system? ..perhaps a diode?

[turniton]

Yucca - you got it! thats it.

i was even thinking of the first caps as being made of double sided copper clad board (nice hv dielectric) and  making the B+ bus lines very wide (increase the surface charge area) directly to the coils and other caps. thus converting as much inductive magnetic collapse to electric surface charge as fast as possible.

maybe even some glass bottle caps (tin foil inside and out) and low esr. Caps can effectively be made out of anything, and no need to buy what can be made cheaply. just be careful to discharge before handling.

the effective staring caps should have small capacitance.

Good building!

Yes, on the diode! fast switching high amp is best.

[turniton]

The Unusual Radiations Produced by Nikola Tesla

http://www.rialian.com/rnboyd/tesla.htm

in Tesla's time there where very small capacitance's, looks like short but wide bus bars. electric fields with amazing ability's and stinging effects. short duration make/brake contacts.  i would imagine caps in the PF or NF range.