HV AC Transformer V2

Specifications:

- Approx 300mtrs of 30SWG 0.315mm Enamel Wire

- Custom made core from 2 TV flyback ferrite cores, approx 12cm long by 10cm high. No inuctance reducing spacers were used.

- Enamel wire wound on custom form made from 6cm of 12mm pvc pipe with 2 8cm perspex discs top and bottom.

- Drive winds are 8 turn copper 13A cable, center tapped for 4 turns either side (4 turns for 12V DC operation)

- Transformer under oil in a plastic tool box. Oil type is Canola cooking oil, which has proved to be a very good dielectric (professional tranformers are starting to use this as well). Approx 3 litres.

- HV Output wires are TV Flyback type, withstanding upto 30kV.

- Coil platform is expanded PVU sheet

- Resonant Frequency is around 39Khz, but has multiple resonance points upto 60Khz.

- HV output at 12V input is around 3kV 32mA, at 24V input it is around 9-12kV 50mA.

 

How it was made:

It did take a long time to construct this transformer as verything had to be right. I went through various designs, until I eventually made this one.

Early prototypes. Both produce different output characteristics	Close up of the 2nd version, notice the close winds	Close up of the 2nd version, notice the layering

Things Learnt;

- Layers need to be made of a fairly good insulating material, pvc insulation tape would be ideal.

- Wide and short coils produce higher output voltages with lower currents

- Thin and tall coils produce higher current output with lower voltages. This is due to a greater surface area exposed to the core flux.

The 3rd version:

The 3rd and final version of the coil is based on having a wide and tall body, to give a good usual voltage and a large current. It was decided that the final transformer needed to be under oil, otherwise arc-over would occur fairly quickly. This was unlike the previous 2 coils that ran fine in open air.

The coil was wound using my Tesla coil winder that I had previously made from TC v1, just using a closer set of holes for the upright wheels.

The insulation tape was of the PVC type and designed for roof repairs, made by Duck tape. Every tenth layer was then followed with a layer of oil resistant paper (used for automobile gasket making) and a layer of PVC tape on top of that before continuing. The winds were layed upon a single layer of double sided Duck tape, to hold them in place and keep the winds as close as possible.

Total winding time = 4 hours

Winds on each layer = 80

Layers = 80

Total winds = 6400

Overall coil weight exc core = 600g

Core construction diagram:

Images:

The finished transformer under oil		A quick test on a jaccobs ladder, pic taken from video.

After running this coil for over a year now, I have not had one problem with arc overs. I feel the transformer could easily be run at over 24V, but I have not needed to yet. The oil has stayed clean, dispite concerns that it may turn rancid. The oil has also seeped into the oil proof paper (aiding in wire heat dissipation? who knows...)

The output arc is very hot and thick (current) and easily starts at 8cm.

Uses:

- Plasma Globes, Tesla Coils, Fluro drivers, Jaccobs Ladders, HV multipliers, Marx Generators etc!

As you can see, it's fairly easy to construct your own HV coil, but does take some time and patience to tune it to your own needs. This is an option if you can't find a suitable off-the-shelf coil to drive your tesla coil.