Re: [TCML] Plasmasonic DRSSTC - Commercial DRSSTC System

["McCauley, Daniel H" <daniel.h.mccauley@xxxxxxxx>]

Hey Steve,

Thanks for the feedback!  Much appreciated!
The MMC design was indeed our largest technical risk item going forward.  I have been closely  monitoring the currents during our testing as well as using thermocouples to monitor the temperature during operation and they are running cool.  Trying to get as many hours on them as possible as well to see if we start getting failures in the long term.

I agree with your concern.  If this was a one-up design, wouldn't be an issue in making a much larger MMC bank, but as this is a production coil, we always have that engineering trade off of performance vs. margin vs. cost, so we are trying are best to maximize performance vs. cost.

Also, we are limiting the duty cycles and PWs on our modulator to ensure these run at relatively low power levels.  If the end customer wants to open it up and let it rip, they are welcome to do that, but for off the shelf operation, operation will be quite conservative.

We are working with a few pulse cap vendors on a custom capacitor, but so far that's been somewhat expensive.  However, we do have a good amount of room if we need to retrofit a different style MMC or larger one.  We can actually go double on the width and have twice the number of strings / caps, albeit at increased cost.

Anyways, I do appreciate you looking at the design.  Your comments and feedback are always welcomed!

Thanks Steve.

Dan




-----Original Message-----
From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On Behalf Of Steve Ward
Sent: Tuesday, August 27, 2013 7:10 PM
To: Tesla Coil Mailing List
Subject: EXTERNAL: Re: [TCML] Plasmasonic DRSSTC - Commercial DRSSTC System

Dan,

Looks like nice stuff, but i have to express my concern over the MMC design.

Im guessing those caps are rated for 500VAC RMS, which is roughly 700VAC peak.  With the 4 in series, thats 2800Vpk AC rated.  Let me make an assumption on operating frequency to be 75khz, giving this capacitor an impedance of 1/(2*pi*75k*.28u) = 7.6 ohms.  The 2800V/7.6 ohms gives 370A max primary current.

This sounds like enough amps to do the sparking that you need, if well designed.  I guess im just suggesting you run the numbers for yourself to be sure that MMC is rated for the intended long-term reliable use.  When ive had capacitor failures (by assuming the DC rating of the caps to be the useful AC peak rating) id get about 40 hours of use before some caps would fail catastrophically.  While a cap loses capacitance to self-healing, the voltage across it goes up higher than the rest of the caps in the string, in essense a positive feedback runaway condition.  This meant id usually lose 1 cap at a time, while the rest of them are significantly weakened, just not dead yet.

Steve


On Mon, Aug 19, 2013 at 7:09 AM, McCauley, Daniel H < daniel.h.mccauley@xxxxxxxx> wrote:

> Hey TCML members!
>
> Just wanted to let you know that we have decided to use popular 
> crowdsourcing website, Indiegogo, to campaign for our new Plasmasonic 
> DRSSTC coil.
>
> The Plasmasonic(R) DRSSTC system is a commercial grade Tesla Coil that 
> is designed specifically for the commercial and educational market, 
> yet attractively priced for the amateur enthusiast.
>
> We would appreciate if you could simply visit our campaign page.
>
> http://www.indiegogo.com/projects/plasmasonic-high-power-musical-tesla
> -coil
>
> Thanks!
> Daniel McCauley
> Eastern Voltage Research
> http://www.easternvoltageresearch.com
> _______________________________________________
> Tesla mailing list
> Tesla@xxxxxxxxxx
> http://www.pupman.com/mailman/listinfo/tesla
>
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