Big Coil


Schematic Daigram

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My big coil is powered by a 15kV 60mA NST.

The specification are:


        0-140VAC Variac Controller

        Transco 15kV 60mA NST

        Input fusing and power factor correction

            15 amp fast blow fuse

            Corcom dual stage AC line filter

            MOV AC over voltage protection

            200uF 180 VAC Power Factor Correction caps

    Charging Circuits:

        Protection Filter

            7 x 1800 volt 2500 amp MOVs on each leg

            2nF capacitance to ground on each leg

            5K ohm 50 watt isolation resistor on each leg

            Safety gap to ground on each leg

    Primary Circuit:

        Primary Cap

            28nF MMC

                5 rows by 10 of 1600V 0.056uF poly pulse caps

                10m ohm 1/2 watt resistor across each cap

        Primary Coil

            19.7 turns of 1/4 inch copper tubing

            Inner dia. 12 inches

            Pitch 0.375 inches

            Tap point 15.1 turns

            132uH inductance


        Spark Gap

            120 BPS Rotary sync gap

            1800 RPM 1/4HP modified Magnatek motor

            Two stationary steel electrodes

            Four moving brass electrodes

            1/2 inch x 7 inch dia. LE phenolic rotor

            Dual stage line filter and MOVs on motor AC input

            Solid oak construction

            Ferrite noise suppression

            Adjustable dwell timing

       Secondary Circuit:

                Coupling to primary  0.145

                System frequency 82 kHz

            Secondary coil

                10.25 inch dia x 30.0 winding length

                1000 turns #24 enameled magnet wire

                32 inch long by 10.25 dia PVC pipe.

                75.4mH inductance

            Top Terminal

                8 inch cord x 30 inch outer diameter dryer duct (used for all calculations and measurements).

                6.5 inch cord x 23.25 inch dia aluminum toroid (Finn Hammer) is shown in photos.