High Voltage Transformers for Tesla Coils

by P. Graham

If you are building a small Tesla Coil there is only a few choices when it comes to the supply. The first would be the Neon Sign Transformer. NSTs as they are commonly known have an output of 5KV to 15KV and around 30mA. They are easy to find and really aren't that expensive to buy. The 15KV, 30mA NSTs are prefered as they have a power output of around 450W. WARNING: NSTs often have the case connected to the centre tap of the secondary, this means the case has half the output voltage of the NST. A simple Jacobs ladder can be constructed using a NST and some Stiff bare wire. Just don't Run the NST for too long arcing this way as an arc provides close to a short circuit and you may damage the NST.

Another choice is the Microwave Transformer. The out put of these is around 2KV with around 500mA output. Parts to build a Tesla Coil can be obtained cheaply with a 2KV rating so they are an attractive prospect. There are two draw backs with Microwave Transformers the first is the fact you have to have your circuit transform 2KV up to 200KV+, the other draw back is the high current. Microwave Transformers can deliver 500mA+ any current above 30mA CAN BE LETHAL. Also take care when dismantaling Microwaves as there is a 2000 volt Capacitor inside them they may still contain enough charge to be lethal.

For large Tesla Coils One can parrallel the above Transformers or find an industrial HV Transformer. One example would be an induction hardening Transformer. Huge Power usually three phase.

Another example would be a pole Pig. These are a step down transformer from a higher voltage down to domestic supply. With these the domestic supply voltage is fed into the secondary which is the low voltage side of the transformer. The primary will exibit a voltage similar to that which is fed into it on the pole. The very last option for a HV Transformer is to wind your own. This may take more effort than it is worth but some builders prefer to build all of their own components. Much planning and understanding of transformer theory is needed to obtain good results. Everything needs to be considered it is more than just the turns ratio.

Warning: Care must be taken when ever working around any voltage capable of causing n electric shock. If You are planning to experiment with High Voltage please take care. It is a good idea to find someone experienced with HV.

About the Author

Amateur Radio Operator in VK (Australia) HV Enthusiast.