Hi Luis,

This is a rather specialized application and there are a number of
considerations which do not come up in more mundane power supplies.

How is the pulse duration controlled? Is there a pulse-forming network
(inductors) or a resistor or some kind of active current control?

Needless to say, this type of device can easily kill and/or mame if you
make a mistake while handling it (or even just one cap) in a partially
charged state.

I may be able to help you out with selecting caps if you can give me more
information about the control of the pulse shape. That will help me to know
how critical the cap esr and esl might be and also whether mixing old and
new might be a problem.

Are the caps pulse rated?

I've built several can crushers and EBW (exploding bridgewire) drivers. I
have not worked with 25kV cap discharge networks, though. Highest was
around 5kV. This device must be impressive - what is it for?

Sean

On Tue, Sep 24, 2019, 3:27 AM Luis Moreira <luis.moreira1575@googlemail.com
wrote:

> Hi all,
> I'm working on a DC pulsed 30KV 50A power supply which uses a capacitor
> bank to store the energy required for the 30mS pulse. Currently it has
> 300uF bank of oil filled capacitors made up of 37.5uF caps in parallel.
> This is an old power supply (18 years old) and I don't really have that
> much info on the caps except for working voltage (32KV), max tested volta=
ge
> (45KV) and capacitance( 37.5uF). I have done some measurements on one of
> the caps using a LCR meter at 100Hz and 120Hz and that confirmed the
> capacitance value and gave me some resistance value also of R =3D120mohms=
.. I
> also got Z and L, although I'm not sure they are relevant.
>
> I need to increase the capacitor bank to extend the pulse time and this
> obviously raises the issue of if I can just order some HV capacitors with
> similar voltage withstand and the required capacitance and add them in
> parallel. My issue is that I don't have any info on working current, peak
> current withstand and ESR.
>
>   looking at the info I have available current can go up to 140A, in some
> conditions, hence I was aiming to get some 300A peak current to have a bi=
t
> of headroom. I can go higher but size and cost may become an issue.
>
> In principle I can't see any issue in adding the new capacitors to the
> existing ones in parallel, they are charged from a common supply and
> discharged via a common busbar, but I keep on having this doubt on
> instantaneous discharging and the effect of different ESR. What do you gu=
ys
> think, am I overthinking it? any insights would be appreciated.
> Thank you.
> Best Regards
>                Luis
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