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# Re: [TCML] MMC reference check.

```James,

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Actually, the truth probably lies somewhere in between what you figured and what your father-in-law said. When capacitors (of equal, or near equal capacitance) are connected in series, their voltage ratings are additive. If you string capacitors of unequal capacitance in series, then the individual units will not share an equal voltage drop and the voltage drop will be inversely proportionate to their capacitance rating (the smaller the capacitance, the greater the voltage drop). Since you are using identical capacitor units, you can figure on each unit sharing a near equal voltage burden.
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So, at the end of the day, your string of (25) 600 volt rated caps would be good for UP TO 15 kV(DC) voltage potential. However, you must consider that the output of a 15 kV NST is AC and like nearly all standard AC potential measurements, is measured as the root means squared (RMS). This is to keep the voltage measurement in compliance with Ohm's law in relation to the current flow and the resistance and/or impedance of the circuit. This means that the peak of each positive and negative swing of the sine wave is actually 1.41x the RMS measurement. This would translate to 15,000(x1.41), which would be over 21,000 volts! You should either upgrade your capacitors for a higher voltage rating or opt for a lower voltage NST, like 9 kV. Of course, a given increase in a capacitor bank's voltage rating, while maintaining the same cpacitance, requires a squaring of the total capacitive energy (E = 1/2CV*2). If you want to double the voltage rating of an MMC bank, while retaining the same capacitance rating, you would need 4x as many individual capacitor units!
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Finally, I'm not sure whether the particular capacitors that you mention are actually suitable for Tesla coil usage? If they are not designed for the rapid cycling, significant RMS and peak currents and intense voltage reversals that are the rule of spark gap Tesla coil firing, they will likely not survive the rigors of a Tesla coil circuit, even if they have the proper capacitance and adequate voltage rating. Others more knowledgable with the part # nomenclautre than myself can probably offer more insight.
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Hope this helps,
David

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----- Original Message ----- From: "James Janota via Tesla" <tesla@xxxxxxxxxx>
```To: <tesla@xxxxxxxxxx>
Sent: Sunday, July 15, 2018 7:42 AM
Subject: [TCML] MMC reference check.

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Ok, the old adage about measuring thrice make cutting nice comes to mind here. I have 25 942c6p15k-f in series. These are rated 600v each. Now my father in law who worked as an electrician for NASA and Inland Steel, said that my configuration won’t be enough for a 15kv NST. With my calculator it said 600x25=15000. But he said each one has to be rated for 15kv each. I don’t want a \$50. Firecracker. I also have 25 1M resistors, one for each cap.
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Regards

James Janota
(727)512-7112 Phone
(727)595-6625 Fax

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