|Lots of delicious ferrite|
The transformer in this case is four transformers in series, each capable of handling ~3KW. The primaries are three turns, and the secondaries are around 150 turns each, so theoretically it will produce 15KV peak when running on 300V primary.
One end of each secondary is tied to each core, and the cores all float roughly 3KV away from the secondary. This makes secondary-to-core insulation a breeze - 3KV can't really do much. Each secondary is wound with 28AWG magnet wire.
The primaries are all isolated from the floating cores. The idea here is that its much easier to insulate a primary than to insulate a secondary (if necessary, the primaries can have insulation on them that can hold off 15KV by sheer brute force!). The downside of this is if there is ever an arcover, the driver is likely to die, and of course, floating cores is death waiting to happen.
My friend Tyler built the driver for this transformer (he also came up with the concept of giant-transformer-for-brute-force-arcs) The driver is an SLR driver using a full-bridge of CM400DU-12F IGBT's running off of 3-phase. To summarize, normally a transformer presents itself as an inductive load (because of the leakage inductance). Driving a purely inductive load is tough on the driver since it will switch at the peaks of the current waveform, leading to tremendous losses and excessive voltage overshoot.
|Soft and almost happy|
In order to prevent this, we kill the ringing after a half-cycle.
And here are the equations to make sure the transformer doesn't saturate:
These equations assume a square primary voltage waveform.