MMC calculator

MMC tank design helper for SGTC, VTTC, DRSSTC and QCWDRSSTC Tesla coils. Results are guidelines to designing a MMC and should always be double checked in your final design!

Inputs are in green. Outputs are in red. Formulas used can be seen below the calculator.

Basic MMC configuration -  Example capacitor Cornell Dubilier
Capacitance uF  942C20P15K-F
Voltage rating Volt
Capacitors in series
Strings in parallel
Results
MMC voltage rating Volt
MMC capacitance uF
Total capacitors
Advanced options
MMC capacitor parameters
Peak current rating A
RMS current rating A
dV/dt rating V/uS
ESR rating
Tesla coil parameters – Example is a medium sized DRSSTC
Frequency kHz
Primary inductance uH
Primary peak current A
On time uS
BPS BPS
Advanced results
Primary impedance
Ohm
MMC Xc (reactance) Ohm
MMC Zc (impedance) Ohm
Actual values MMC rating
Voltage over MMC Volt Volt
RMS current MMC A A
dV/dt for MMC V/uS V/uS
Peak current for MMC A A

Math used

MMC voltage rating: MMC voltage rating = voltage rating * capacitors in series.

MMC capacitance: MMC capacitance = (single capacitor capacitance * amount of capacitors in parallel) / amount of capacitors in a string.

Primary impedance: Zprimary = SQRT(Lp / Cp).

MMC Xc, reactance: Xc = 1 / (2 * PI * F * C). F is frequency in Hertz. C is capacitance in Farad.

MMC Zc, impedance: Zc = SQRT(ESR^2 + Xc^2). ESR is the combined ESR for the MCC. Xc is the MMC reactanse from above.

Voltage over MMC: Voltage over MMC = Zc * primary peak current

RMS current MMC: Irms = 0.5 * primary peak current * SQRT(on time * bangs per second). Steve McConner.

dV/dt for MMC: Actual dV/dt the MCC sees = (primary peak current / amount of capacitor strings in parallel) * amount of capacitors in a string.

Peak current for MMC: Peak rating = capacitor peak rating * amount of capacitor strings in parallel.

3 Responses to MMC calculator

  1. Pingback: MMC calculator added to the online calculators | Kaizer Power Electronics

  2. Jay says:

    When you calculate dv/dt why do you use (primary peak current / amount of capacitor strings in parallel) * amount of capacitors in a string

    Why not use 2 x pi x Vpeak x Frequency

    It just really looks odd to me how you are factoring parallel capacitors into a dv/dt and that you are completely ignoring frequency.
    Perhaps my brain is missing some critical hunk of information.

    Thanks for any help.

  3. Mads Barnkob says:

    Hey Jay

    Thanks for pointing out that I did make a mistake in my calculator, the current dv/dt calculation is only the combined dv/dt value for the mmc which then was to be used in a equation.

    Kind regards
    Mads

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