Hello Tyler,
You want one that is pulse rated at a minimum of your spark gap discharge rate (> 120 PPS). Many energy discharge capacitors are only rated for a few pulses per second and have very limited lifetimes, some as few as 10,000 bangs. I know that the Maxwell 37xxx series are pulse rated at a minimum of 500 PPS. I use 6 of the model 37667 in a series-parallel arrangement. Of coarse you can go ahead and try others and hope for the best but considering that even used Maxwells are not cheap, I wouldn't take the chance unless you can get the voltage rating much higher than normal to reduce the stress. I would want at least a 50 KV rating for a capacitor rated for your PPS. Consult the Maxwell data sheets to find out the maximum pulse rate and lifetime. Having said that, I have seen a number of coils use Maxwells that were not really rated to at least 120 PPS with quite low lifetime bang ratings and seem to operate without a problem. Maybe they are way under-stressed which increases their lifetime.
Looking at your list, you can immediately discard the 125 uF and 5.4 uF ones. The capacitance is much too large and would require almost no turns on the primary coil. The remaining ones are possibilities if they are properly rated as previously mentioned. The most interesting one that I see on your list is the 0.118 uF, 100 KV one. Given its high voltage rating, this is probably the one that will give the longest lifetime even if it is rated below 120 PPS and has low rated bang life. It also has the next to lowest capacitance on your list which is good because you may still have a reasonable number of primary coil turns to work with. Consult JAVATC to see how many primary coil turns you will need. The number will be quite small and will make the tuning very sensitive to your tap position on the primary coil.
Steve White
Cedar Rapids, Iowa
----- Original Message -----
From: "Tyler LaVite" <tlavite@xxxxxxxxx>
To: tesla@xxxxxxxxxx
Sent: Friday, December 21, 2018 4:46:17 PM
Subject: [TCML] Maxwell pulse capacitor
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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