On Wed, 13 Aug 2003, Dave Tweed wrote: > Vasile Surducan wrote: > > I need to generate 2KVrms into a small capacitive load (below 1nF). > > So far I have good results with a resonant output, voltage to current > > converter. The problem I have is that I need a precise way to control > > the generator output inductivity (other than changing the coil wires > > numbers or the air gap in the ferrite core) to cover the whole frequency > > range. > > You're kidding, right? > > You'd need >25H of inductance to resonate with <1nF at 1 kHz. :)))) Of course not. The ferrite I have on the table definitely does not have 25H. And the load is 1nF. But also in paralel with the load I can have any capacitor value I want if the Q remains high. So don't worry about that ! > > Also, your <1nF load draws over 300mA rms of reactive current at 25 kHz, > which is going to need relatively large wire to keep losses low. > I think you have mistaken with 10^3. Is just about 250 microamperes... > If you add load capacitance to solve the first problem, the current levels > will rise, exacerbating the second problem. > No, it's ok, do again your computation if you have the pleasure. > > Do you know other methodes to get such high voltage in the > > frequency range required ? > > Yeah, you're going to be better off getting a broadband audio power > amplifier and using a beefy audio transformer to step the voltage up. > Perhaps the output transformer from an old tube-type amplifier hooked > up backwards, although one that handles ~630 VA at 25 kHz may be hard > to find. This is not working. One of my coleague has project and built such an amplifier 5 years ago. Just in 0...10KHz but up to 10KV. The system is totaly instable with capacitive loads. It works only with resistive loads. > > An alternative approach would be to create a DC supply of 3KV (900 watts) > and then build some sort of H-bridge driver out of high-voltage tubes. > But controlling distortion with this setup might be a problem. > This is not feasible at all. And you know well why :) thank you, Vasile -- http://www.piclist.com hint: To leave the PICList mailto:piclist-unsubscribe-request@mitvma.mit.edu