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Re: [TCML] MMC Caps

Thanks Mark,
I will look into the 942C you mentioned, I was not aware of them...

The coil I am aiming to build will produce 2.5 meter arcs, which in itself is not that big... The cap has to be this large (or larger) due to the low 1200v DC applied to the tank circuit, or the "bang" energy in the system would be too low per pulse to achieve the arc length...

This is standard for OLTC... huge tank cap, tiny inductance in the primary...

Although the tank is fed with DC, the caps still see the HF AC every time the tank is fired, hence my concern for the caps when running at 1200v.



On 2013-10-20 09:21, Mark X2 wrote:
Hi Carlos,

20uF, that's quite impressive.
How big of a coil are we talking about, just curious?

Why the 940C instead of the 942C? The 942C has better specs, considering
ESR, dV/dT and max. current.

The manufacturer's voltage ratings are very conservative and you're using
DC, won't be much of a problem then.


2013/10/19 <lightningfor@xxxxxxxxxxxxxxxxxxxxxx>

I am building a large OLTC with about a 20uF capacitor.
I want to run about 1200vDC so I can make use of the 3ph power I have

I will be using the familiar 940C style of cornel Dublier capacitors all paralleled up to give me the 20uF, but I remember Steve HV recently saying
that caps do breakdown after some hours of use if run beyond the AC

The problem is that when we serries them up to increae the voltage rating,
it means we need LOTS of caps so more $$$$...

The common cap is 940C20P47K-F, 0.47uF 2000v DC, 550vAC rated... (so I
need about 170 caps in serries/parrallel)
But there is also a 940C30P15K-F, 0.15uF 3000v DC, but the AC rating is
still 550vAC...? (so I need about 130 in parallel.)

Do you think I can RELIABLY run 1200v DC into the 3000v DC caps, or should I just bite the bullet and pay the dollars to serries/parrallel the larger
2000v DC caps?


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