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Re: The right capacitor match?



Original poster: "Gerry  Reynolds" <gerryreynolds@xxxxxxxxxxxxx>

Hi Ethersmith,

If you already have the 940C series and dont mind losing them then by all means try them. The 942 series is the prefered caps these days. Keep in mind that a 15KV NST is a RMS spec and the peak voltage is 1.414 times larger (21.2KV). Also, if you plan on using a variac and giving the NST a 140V input, the peak voltage should be scaled up accordingly. I design my MMC strings for 28KV using a 15KV NST but I run my SRSG at 24KV.

Gerry R.

Original poster: "Ethersmith" <siveya@xxxxxxxxxxxxxx>

Greetings,

New coiler here, hoping to find some aid.

I have a 15K/30mA NST which I am building an MMC for.

Given LTR of 1.5* I have come up with a match in the range of .008mF

I have had trouble finding HV caps in the lower Farad range. (Any current
suggestions would be greatly appreciated).

I have found some Cornel Dubilier (940C30S47K) "Snubber Capacitors" that
look like they will work. They are not on Terry's known Bad Caps list. They
are rated at 3kv .047mF

If I have done my math properly, I only need six of these in series to get a
capacitance of .00783mF (which is in my LTR range) and a voltage of 18,000v
(which exceeds my NST voltage)

This seems small and cheap compared to what others seem to need regularly.
Is it just that my coil is one of the smaller ones out there? Or have I made
some egregious error?

Your input is golden.  Thank you.

--Ethersmith