[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [TCML] MMC building - some questions

Hi Thomas,

I don't see a reason why you couldn't do this if it's just one or two caps at the ends. You must however consider the voltage division in the series string.

Say you use 11 of the .15uF 942C series caps. As you know, Ct = .0136uF.
Also say you have 10000Vp across the string, then ideally you have 909V across each cap as Vc=Ct/C x Vt.

Now parallel parallel cap with #11. You still have 11 caps in series with the last cap pair having a value of 0.3uF.

Ct ends up at 0.0143uF.
The voltage across the first 10 caps in the string increases to 953V and the voltage at the paired caps is 476V.

Should be ok from a voltage standpoint, but it's important to evaluate the voltages seen across each cap.

V1=Ct/C1 x Vt,..... V2=Ct/C2 x Vt, .... etc...

However, don't put too few of caps in series. 11 caps isn't much and may put a decent voltage stress across each cap. Also, the voltage seen across the remaining non-paired caps increases significantly with fewer caps in a string. Hopefully, your using a low peak voltage as in the example.

Trying to tweak capacitance can be difficult compared to simply adjusting the primary inductance. The slight difference in C with a coil isn't important. It's easier to ball park the needed capacitance and adjust the primary.

Take care,

Thomas Ryckmans wrote:

I am now building my MMC. From previous JavaTC calculation, I need about
0.013 uF to reach resonance. Since I am using CDE capacitors
942C20P15K-F (2000Vdc 0.15 uF) I would need a single string of 11 caps to
reach 0.013 uF and have a (recommended) voltage rating of 22kV.

Since 1/Ctotal =1/C1+1/C2+... 1/C11 I have
1/Ctotal = 11/Cn = 0.0136 uF

The question is: can I put ONE extra cap in parallel with another within the
string to tweak the total capacitance if needed? In effect, one cap in the
string becomes a larger cap, with twice the value at 0.3 uF

1/Ctotal = 1/C1+1/C2+. 1/C11 with say, C1= 0.3 uF and the others at 0.15 uF

Then 1/Ctotal = 0.01428 uF

A small sketch is here:


Could this be an easy way to tweak my tank cap value, adding caps in
parallel to caps in the initial string to a max possible of 0.027 (which is
equivalent to two strings in parallel)

Many thanks


Tesla mailing list

Tesla mailing list