Re: How good are MMC caps ;-))

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Terry Fritz <vardin@xxxxxxxxxxxxxxxxxxxxxxx>

Hi,

At 11:48 PM 8/19/2005, you wrote:

> Hello,
>
> I have a couple of questions.
>
>
> 1.        Are bleeding resistors required for balancing if all 
> capacitors are the same?

They are mostly for safety.  It is possible for there to be unequal 
charges on the caps so voltage may be left on them unless they are 
all individually drained.  If two capacitors are in series, one could 
be at -2000V and the other at +2000V.  Even though the far ends are 
at zero volts, the two capacitors are fully charged.

Since the resistors cost $0.01 each (or free) there is no reason not 
to use them.

There are many arguments as to how the string could develop unequal 
charges such as corona, cap failure, streamer hit...  The resistors 
simply insure that the cap is totally discharged within say 10 
seconds after the power is removed.



> 2.        Do bleeding resistors not take away some energy?

(2000 / SQRT(2))^2 / 10E6 = 0.2 watts.  So If you coil has say 20 of 
them they will dissipate 4 watts.  That might be say 0.5% of a coil's power.

Some people are using 2 resistors per cap which gives 1/2 the power per cap.

The power cord to the coil has far more loss than the resistors...


> 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)

The resistors are free.  I imagine they could be soldered on faster 
than a solenoid arrangement could be thought out.  They don't "screw 
up" and not work.

I don't know of any advantage to go with the solenoid.  Invest the 
money in big power cords ;-)

Cheers,

        Terry




> Best regards,
>
> Sebastiaan