From 7mm dia PCB to kVAs...
I've a requirement for a 'small power' AC generator:
- sine wave
- frequency 5kHz to 50kHz
- voltage output up to 25kV peak The load is roughly 150pF, with small losses (almost a glass capacitor).
Gasp, the 150pF load translates to 1.1A at 50kHz/25kV and that's 27.5kVA of circulating power.
The 1:10 frequency range (might reduce to 10kHz-50kHz so a 1:5 ratio) almost prevents using resonance as this would translate to a 1:100 tuning cap ratio, with an already highish starting value, and a variable inductor at those voltage levels is sure impractical.
At 5/10kHz step up transformer will have a big core section and can't be ferrite: the low saturation induction will call for high secondary turn count and with the required high isolation that will make for high leakage inductance which won't go with the 1A current. More, if low enough leakage inductance were possible, the step up ratio, (say 50 with a 500V primary supply) will make for huge current and losses at the high frequency end.
One thing I'm thinking about is, apart from using nano-crystalline core material (saturation around 1T) in order to cut on turns count, is to size the transformer so that its secondary side leakage inductance resonates slightly below the 50kHz limit, say 40kHz, with the 150p load cap. That won't reduce the primary current, still 50A, but will reduce the necessary primary voltage, hence losses...
What do you think. Any other cute idea?
Oh, it's a one off.