# [TCML] further help with dual mot

Scott Bogard sdbogard at gmail.com
Sun Sep 4 14:27:11 MDT 2011

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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