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Re: Dual MOT plans - PIRANHA



Original poster: "resonance" <resonance@xxxxxxxxxxxx>





Yes, as Terry points out, we use a series inductor to limit the MOT peak currents. Not difficult to make, 18 inch long, 2 inch ID PVC tube, filled with cut 1/8th inch dia. steel rod. You coat each steel piece by dipping them into some Dolph's AC-43 and then allowing them to air dry --- hang them on clothes line with clothes pins. This helps prevent eddy currents and overheating the steel rod. The steel rod is cut to 17.5 inches length and then siliconed on each end of the 2" ID PVC tube. I also use a pair of 60 turn "hash chokes" on each pri lead with separate varisters to clip any "nasties".

We wound approx 150-200 turns of #10 AWG on each tube in 3 layers. I like to use some cut 3/16th inch square phenolic strips between each winding so I can run a small 150 CFM blower pumping air thru the reactors for extended run times. Exact number of turns will depend on the quality of your steel and the characteristics of your MOT, so experiment with this value.Set up a small climbing arc and test for optimum short circuit operation limiting current to 18 Amps max. This will hold the MOT short circuit current to 18 Amps allowing smooth back-back SCR power control without oversaturation peaks hitting in excess of 20 Amps and blowing circuit breakers.

We run the pri off two separate 120 VAC circuits and hook the secs in series for 4 kV output at 4.3 kVA.

Dr. Resonance

SISG's and PIRANHA class coils can run at any power level depending on the number of SISG sections used. It is about 6 inches of arc multiplied by the number of sections minus the toroid radius. So one of Mark's SISG boards would be fine for say an 18 inch arc coil. You would need a small variac or one of the solid state variac boards Dr. R. mentions for control. The basics of the SISG are here:

http://drsstc.com/~sisg/files/SISG.pdf

I never got further on "my" solid state variac thing. I "think" DC's needs a charging choke where mine would not.