# Re: [TCML] Maxwell pulse capacitor

```I have always wondered what those 1 PPS capacitors were originally used for. Laser fusion experiments, EMP generators, rail guns, Marx generators? Does anyone know?

Steve White
Cedar Rapids, Iowa

----- Original Message -----
From: "Bert Hickman" <bert@xxxxxxxxxxxxxxxxxxxxx>
To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
Sent: Saturday, December 22, 2018 9:21:55 AM
Subject: Re: [TCML] Maxwell pulse capacitor

Tyler,

Your pulse cap should have a DC rating that's at least 3X the maximum
RMS output voltage of your pole pig. Assuming you're using a transformer
that outputs 14.4 kV. If you plan to overdrive your primary to 280 volts
from your variac, shoot for 50 kV caps (or higher).

In order to efficiently use the power your pig can deliver, the bang
size needs to be fairly large. For example, suppose you want to operate
your coil in the range of 10 - 20 kW using a maximum break rate of 240
BPS. Under these conditions, the bang size can be estimated as:

Jmin = 10000/240 ~ 42 joules/bang
Jmax = 20000/240 ~ 84 joules/bang

Assuming your gap breakdown voltage is 18 kV, this means your tank cap
size should be about the following:

Cmin = 42*2/(18000^2)  = 0.259 uF
Cmax = 84*2/(18,000^2) = 0.518 uF

As Steve mentioned, the Maxwell 37XXX series have PPS ratings of 500 -
1000 PPS and are the best choice for TC use. Some 31XXX series caps will
also run at 100 - 400 BPS, such as 31393, 31507, 31662, 31677, 31687,
31892, and 31981(all 100 PPS), and 31583(400 PPS). I would NOT recommend
using any caps rated for 1 PPS, since they can overheat and quickly
self-destruct from internal heating before the outer case even has a
chance to get warm.

You can play with the above calculations above to see what works best

Good luck and best wishes,

Bert

Tyler LaVite wrote:
> I’m buying a maxwell pulse capacitor for my 25kva pole pig. Couple options here which is the best one to buy these are what’s available.
>
> 125uF @ 40kv
> .25uF @ 50kv
> .118uF @ 100kv
> .101uF @ 40kv
> 5.4uF @ 20kv
> .252uF @ 50kv
> .251uF @ 50kv
>
> What are your guys thoughts on the best one for just messing around no specific use maybe possibly use it in a larger Tesla coil then my current one this summer.
>
> Sent from my iPhone
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