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Re: [TCML] further help with dual mot



No, because a Tesla coil is not a dead short, it only acts like a dead short for a millisecond when the tank cap is fully discharged, after which the charge in the cap, "pushes back" against the transformers, limiting current, and keeping your breaker happy (a smaller cap increases this effect, which is why I'm in no hurry to make my 81nF bigger.) You will still flip breakers, but it takes me about 45 seconds of continuous run to flip a 15 amp breaker, and I am making 60 inch sparks using a variac to overdrive to 140V input... If I shut down for a minute between runs I can go like this for an hour without ever flipping a breaker.

Scott Bogard.

On 9/4/2011 7:14 PM, James Hutton wrote:
The breaker on my power grid thing flips if I pull a continuous arc for over 5 seconds. Will this not happen when I run the coil or the gap?

Date: Sun, 4 Sep 2011 16:27:11 -0400
From: sdbogard@xxxxxxxxx
To: tesla@xxxxxxxxxx
Subject: Re: [TCML] further help with dual mot

Hi James,
       Firstly if you are only using two MOTs you don't need a ballast at
all for maximum power, they draw just enough to not flip breakers for
short runs.  Secondly the standard ballast for two MOTs is one MOT, with
the secondary shorted.  You basically use the primary as a resistor,
that way the inductance limits your current, no matter how many MOTs you
have down wind, to that of a single MOT or around one kilowatt.  Lastly,
Yes, you can use a resistor, but good luck finding one that will handle
the heat dissipation (remember power = current squared times
resistance.)  You are going to want at least a thousand watts, any less
and there is no point at all in using MOTs.  As for 8 ohms, lets see.
1000 = I^2*8, so 1000/8=I^2, so 125=I^2, so I=11Amps, so yes, you can
use an 8 Ohm resistor.  You might need to make a salt water resistor,
that is the only economical resistor I can think of for that heat
dissipation, and I'm not sure you can tritate it for an exact value like
8 ohms.  In the end I'd use an inductive ballast, or no ballast, and
just let the coil draw what it wants, smoothest operation that way, and
the only way you can expect to get really big sparks out of 2 MOTs...

On 9/4/2011 12:28 PM, James Hutton wrote:
If I were to use a resistive ballast, would an 8 ohm resistor work?I am going off rishie burnett's site: http://www.richieburnett.co.uk/ballast.html#ballastingLV current = LV supply voltage / Ballast resistance.15 = 120/8

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