Pulse power > Capacitor Banks

My first and only capacitor bank

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Here is my 64uF @ 4270v capacitor bank. It has 3 options on top for firing: a cylindrical coil for can crushing, a pancake coil for ring launching, and two clips for attaching wires to be exploded (with blast shield). There is a switch on top to select the desired option. It is discharged using a high voltage relay that I added tungsten contacts to so they wouldn't ablate themselves away. There is a hv diode acting as a half wave rectifier for the charging circuit. There is also a 5 megaohm hv resistor across the caps acting as a bleeder for safety, and an Incandescent bulb in series with the charging primary acting as an indicator of level of charge. It crushes cans ok, and launches rings pretty well. It will also explode wires fairly well if they are small enough.

What would be a good way to indicate when the cap bank is fully charged, other than checking the brightness of the bulb in line with the hv primary?

Nice build, I like how the terminals on top kind of look like some lego bricks.  ;)

The obvious solution for getting the state of charge is to just measure the voltage through a voltage divider (made from HV resistors).

You could also measure the capacitor voltage relative to the supply to get the difference between them.

If you don't want to deal with any high voltages you could also put a current shunt on the low side of the charching voltage.
This way you can measure the current which should go to 0 when the caps are fully charged.
Being in the lowside, you can simply hook up a multimeter directly across the shunt.

A more theoretical approach might also be to monitor the charging voltage and current and integrate the energy that has been transportet into the caps.

I hope this gives you some ideas on what might be interesting to try.  :)

I like the idea of the current measurement of the low end of the charging circuit. I guess that is what the bulb currently indicates (pun intended) but it would be great to have some numbers to go along with that. I did some YouTube learning about shunts and ammeters and how all that works. That'll be the next addition.

Another question: I currently have the half wave rectifier on the hv end of the charging circuit. Would it make any difference or be better if I put it on the low voltage end? And would the fact that it is half wave rectified with no smoothing cap affect the current reading?

On a different note, I'm trying to figure out more things to use this capacitor bank for. So far I've crushed cans, exploded wires, launched rings. What else could I use this for? Thanks!

I built a pulsed power generator several years ago. It can store up to 24,000 joules. I use it to shrink coins, crush cans, and launch discs. I use a NST to charge the capacitor. To monitor the charge level, I use a microammeter with a 25 microamp scale. I place a 1 gigaohm HV resistor in series with the microammeter. In doing so, the meter now reads in kilovolts instead of microamps. I just watch the meter as I apply charge.

I use two meters. One meter is for monitoring the voltage level of the capacitor during charging. The other meter is for monitoring the capacitor voltage level during bleed-down. The bleed-down meter is bipolar to allow for the possibility of positive or negative residual charge on the capacitor due to voltage reversal. The charging meter is disconnected during firing and bleed-down. The bleed-down meter is only connected during bleed-down.


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