RE: How good are MMC caps ;-))

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Lau, Gary" <Gary.Lau@xxxxxx>

Bleeding and balancing are two unrelated things.

The mechanism by which unequal charges remain on individual MMC caps is
not understood.  It is not due to unequal capacitance values.  In my
experiments, some capacitor types are prone to developing these charges,
and others are not, using exactly the same cap values and test circuit.
I have no idea what causes this difference.

I would recommend using bleeder resistors across individual caps.  If
you used a cap that did not produce unequal residual charges (and knew
that for a fact), you could use a single resistor, but an overall
bleeder would still be useful to ensure that a fault condition did not
leave a net charge on the cap.  I would strongly discourage using a
solenoid to connect the resistor.  Making it more complex than needed
makes it more likely to fail, and building a switch capable of switching
20kV+ is non-trivial.  The amount of power wasted by bleeders should be
insignificant compared with the other losses in the circuit.

Regards, Gary Lau
MA, USA


> Original poster: Illicium Verum <sebas@xxxxxxxxxxxxxxxx>
>
>
> Hello,
>
> I have a couple of questions.
>
>
> 1.        Are bleeding resistors required for balancing if all
> capacitors are the same?
>
>
> 2.        Do bleeding resistors not take away some energy?
>
>
> 3.        What are the advantages or disadvantages of using one big
> MMR (Multi Mini Resistor) connected in parallel with the MMC AFTER
> using the tesla coil with the purpose of discharging? (I was thinking
> on a solenoid based circuit that connects the MMR over the MMC after
> power shutdown)
>
>
> Best regards,
>
> Sebastiaan
>