Re: MMC Question

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: mark@xxxxxxxxxxxxxxxx 

Quoting Tesla list <tesla@xxxxxxxxxx>:

> Original poster: "huil888" <huil888@xxxxxxxxxxxx>
>
> Mark -
>
> A few questions on your TC:
>
> 1. Are you absolutely sure that your HV transformer is rated 15kV at
> 20ma?? This is an extremely unusual rating for a NST, in 10 years of
> Tesla coil building I have never heard of a NST with this rating in
> North America, Europe, or the UK. Or is it not a NST? There are some
> relatively small (8" X 8" X 8") DC power supplies for air ionizers
> that have similar ratings, but these may not be suitable for driving
> a Tesla coil. Double check the nameplate, let me know who the
> manufacturer is and what the nameplate says.

Umm your correct about the xmfr I'm not 100% sure it will work 
however NST's are
a tad rare in the UK.  The make is INTEGRAL Plus and is rated correctly at 15Kv
20mA

>
> 2. How did you determine that 0.0042uF was a "resonant" capacitor
> value for your transformer? My data indicate that 0.0035uF would be
> the resonant value with a 15/20 transformer.

Looks to me as if you used 60Hz for the line frequency In the UK we're running
on 50Hz
>
> In any case, these variations in tank capacitor "value" (technically
> more correct than "size") have no significant affect on eventually
> tuning your system. The inductance of the primary coil is "adjusted"
> (via variable tap point) to make the resonant frequency of the tank
> circuit match the resonant frequency of the secondary coil with topload.
>
> Are you using one of the Tesla coil design programs to design all the
> critical parameters of your coil? If you don't have an oscilloscope
> and RF signal generator, it is VERY important to carefully calculate
> the dimensions and values for each component, or you will have a very
> difficult time "tuning" your coil to achieve resonance.
>
> WINTESLA is a very simple but useful program, JAVATC is even more
> powerful but slightly more complex. I would suggest that you design
> your coil COMPLETELY on paper before you proceed with any more
> construction. The biggset single source of failure with tesla coils
> is not having the primary and secondary circuits tuned to EXACTLY the
> same resonant frequency. This will not happen by lucky accident;
> these circuits need to be very carefully designed and constructed to
> achieve resonance. Without resonance, there will be no sparks. Period.

I totaly agree I've been using a number of programs as well as crunching the
numbers by hand, most of the programs seem to give slightly different results,
but all are probably near enough not to make to much difference.  I've been in
the construction phase for about 6 months. I'm not someone to rush these thing.

In fact I've only built a terry filter and MMC, and will be winding the
secondary soon, as the weather improves, as my workshop is quite cold still.

But many thanks for the comments and concern.

Regards

Mark
>
> Regards,
> Scott Hanson
> Costa Mesa, California
> USA
> ----- Original Message ----- From: "Tesla list" <tesla@xxxxxxxxxx>
> To: <tesla@xxxxxxxxxx>
> Sent: Monday, April 23, 2007 12:26 PM
> Subject: MMC Question
>
>
> >Original poster: mark@xxxxxxxxxxxxxxxx
> >Hi,
> >
> >I've just built my MMC for my first Tesla coil, and I have yet
> >another question
> >regarding its construction and use.  From what I've read the MMC makes part
> of
> >a tuned circuit.  My original question, was regarding the size of
> >MMC required,
> >and someone from the list recommended making it 1.5 - 2x bigger than
> required.
> >
> >so my original size was
> >
> >0.0042uF for a 15Kv 20mA 50hz xfmr
> >
> >so timed this by 1.5 and got 0.0063uF
> >
> >However I mucked up the calculation and didn't realize until after I built
> my
> >MCC, I've ended up with 0.0055uF
> >
> >So my question really is, will this still work correctly or do I need to
> start
> >again ??
> >
> >And if this needs to be in tune with the rest of the circuit, surely even
> >increasing this 1.5 would muck the tuning up??
> >
> >Any comments appreciated.
> >
> >Mark
> >
> >
>
>
>
>
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