Hi John,The 0.0088uF size for a 9/30 is the capacitance that will cause transformer resonance to occur. This is dangerous for the NST. NST's normally die due to the insulation not capable of withstanding voltages much beyond it's peak rating. This is why we often recommend running a cap that is larger than this resonance value (LTR) as it prevents transformer resonance. For a static gap, the recommended size is .013uF.
Regarding caps in series and assuming all the same type: The voltage doubles and the total capacitance divides by the number of caps.
Two of your .15uF/2000V caps in series = 0.075uF at 4000V.Regarding caps in parallel and assuming all the same type: The voltage remains the same and the total capacitance multiplies by the number of caps.
Two of your .15uF/2000V caps in parallel = 0.3uF at 2000V.Regarding your idea of 5 CD caps in a string for .03uF. Yes it will be .03uF. Yes it will be rated for 10kV. But, it will DIE!!! The 9/30 will output a peak voltage of 9 x 1.414 = 12.7kV! Also, these are disruptive systems and high voltage transients do get back to the NST even though we do our best to attenuate and filter them out. You want to ensure that your cap voltage rating is 2 to 2.5 x the peak voltage rating of the NST, otherwise cap life can be shortened. You can get away with bare minimum, but I personally don't advise it because it's risky.
Regarding your question about building too big. When it comes to the voltage rating of the MMC, the bigger the better! When it comes to the capacitance of the MMC, well that is limited. Larger capacitance takes longer to charge and lowers bps. In order to fire across the gap, shoot for approximately 120bps. If you do that, you'll find that your range of capacitance can't go too much higher than the stated LTR size. You can go a little larger and it might do well even if the bps drops a little, but there is a limit. You can also go smaller, but again, there is a limit and the smaller you go, the further into transformer resonance you get. There are some advantages to both, but it really helps to understand how to take advantage of resonant charging or even just high joules with larger caps. Richie Burnett's website is highly recommended on these topics.
http://www.richieburnett.co.uk/tesla.shtml Take care, Bart John Matok wrote:
I'm a little confused when it comes to designing an MMC. I think I understand the basics behind it. Add them in series to increase the voltage rating, and add them in parallel to increase the capacitance (The wikipediapage on caps really helped).I'm starting to design my MMC and trying to grasp the concept behind it. I'm using a 9/30 NST. I used the cap calculator on deepfriedneon and found my needed capacitance to be .0088uF (does that sound right?). My question is this: Do I build my MMC to match my NST's rating? For example, if I bought a bunch of Cornell-Dubilier 942C20P15K-F caps rated 0.15uF@2000V each, could I stick 5 of them in series to get an MMC rated at 10,000KV and .03uF? That seems quite high for the capacitance needed (.03uF compared to .0088uF). Am I wrong to try to build an MMC to be rated at .0088uF and 9000KV? Should it be higher? Part 2 of my question: What are the consequences of making an MMC way to big for your needs in a Tesla Coil? Lets say that I hypothetically built an MMC rated at 20uF and 25KV. Would that effect my coil any different than having a decent, very sufficient cap (.008uF@9KV) my coil? I wouldn't mind buyinga few extra caps to give myself some piece of mind.John Matok _______________________________________________ Tesla mailing list Tesla@xxxxxxxxxxxxxx http://www.pupman.com/mailman/listinfo/tesla
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