Dan's Ten Inch 3.5kW Tesla Coil

"The Ten Inch Coil"\\

Introduction

No more wimpy coils. Time to build something big. The main goal of this tesla coil is to build something impressive which at

the same time can be easily transported for demonstrations. I was originally going to use a 3kVA to 5kVA pole transformer

for this tesla coil, however, due to the fact 240VAC is not as easily available as 120VAC and the fact that pole transformers

are very heavy, I opted to use a GE Potential Transformer which only weighs 100 LBS.

HV Transformer

GE Potential Transformer

Primary 14.4kV

Secondary 120V

Rated for 1.5kVA, but will run up to 3.5kVA for short durations.

Output current: 200mA (with ballast)

Weight: 100 LBS (and a brutal 100 LBS at that!)

Safety Gap

The safety gap will be placed at the HV output of the transformer and protect

the HV circuit from over-voltage transients.

Ballast

500ft, 12 AWG spool of wire

First tests with this ballast yield about 25-30A input current to the HV Transformer.

Primary Tank Capacitor

The primary tank capacitor I am using is the MMC capacitor shown above.

To create this new MMC, I used twelve (12) 0.33uF, 2kV capacitors in series to create a 0.0275uF, 24kV MMC.

The capacitors used are GE 42L3332, 0.33uF, 2kV Poly Capacitors. These can be obtained at Newark Electronics

(www.newark.com) for about $4.50 each.

The MMC capacitors shown below are my back-up primary capacitors. The top one is identical to the MMC capacitor shown

above while the bottom one is a 0.015uF, 20kV MMC created using ten (10) of the Geek Group's 0.15uF, 2kV Cornell Dublier

capacitors.

3kW 120VAC Power Controller

This is a dedicated 3kW power controller which can control both the HV Transformer and the ARSG

spark gap. Front controls include E-STOP, safety key switch, and variacs for both the HV Transformer

output and ARSG output. For more detailed information and schematics, click here.

Asynchronous Rotary Spark Gap (ARSG)

The ARSG is fully adjustable and stable for speeds up to 3600 RPM (480 BPS). For normal operation,

I only anticipate operating up to 1800 RPM (240 BPS). Maximum no-load speed is 15000 RPM, however I'm

sure this ARSG would self-destruct if it could actually reach that speed. For more information and pictures on

the ARSG, click here.

Toroid

Here is my first attempt at a homemade toroid. It is approximately 32" x 4" in size and has an approximate

capacitance of 30pF. Click here for my article on homemade toroid construction.

Secondary Coil

Here is my new ten inch secondary. The toroid is only on top for

decoration. I'll be using a larger toroid during actual operation.

Here is me winding my ten inch secondary using the "poor man's" coil winder. Although its hand powered, its very efficient

and extremely easy to wind large coils with. This secondary only took about one hour to wind by hand.

The "poor man's" coil winder. Note the comfy seat which is paramount to this coil winder design.

10" diameter cardboard sonotube

45" secondary winding length (H/D aspect ratio: 4.5:1)

Secondary Inductance vs. Frequency Plot from HP Impedance Analyzer

Secondary Tuning Specification

The secondary coilform was first coated with three coats of orange shellac and then wound using the "poor man's"

coil winding machine. Following that, the secondary was coated many coats of polyurethane.

More to come soon . . .

Last modified August 16, 2005 08:05:20 PM