How to design a 7.5kV AC source? - Page 1
Forum section: electronics / projects

author: CristianM
author_rank: Newbie
timestamp: January 18, 2019, 02:40:00 pm
content: Hello! I need to design a high voltage AC source with the following specifications:- 7.5kVpp max. output voltage;- adjustable output voltage;- isolated output;- sine wave output;- adjustable output (sine wave) frequency in the range 40Hz-2kHz;- max. 1 mA output current.Can someone recommend a possible solution? A basic transformer or flyback supply (maybe recommend some components, schematics) or even a commercial solution?

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: January 18, 2019, 02:46:06 pm
content: capacitance is going to be an issue at 2Khz, so you may need some care in how the windings are done.

author: CristianM
author_rank: Newbie
timestamp: January 18, 2019, 02:49:46 pm
content: Quote from: mikeselectricstuff on January 18, 2019, 02:46:06 pmCan you detail your answer/provide a design example/guidlines?

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: January 18, 2019, 06:59:38 pm
content: Quote from: CristianM on January 18, 2019, 02:49:46 pmwith 7.5kv bouncing around at 2khz, the capacitive reactance will be significant load.e.g. 10pF at 2KHz has a reactance of around 8M, which will draw a little under 1mA at 7.5kv, so that alone doubles your input power requirement. And the capacitance may be a lot more than 10pf.With the large inductance of the secondary you also need to make sure that you're nowhere near the resonant frequency of the secondary inductance and the stray/load capacitance, or bad things will happen.

author: SiliconWizard
author_rank: Super Contributor
timestamp: January 19, 2019, 12:19:18 am
content: http://www.trekinc.com/products/PD05034.aspNote: this is costing an arm and a leg.

author: NiHaoMike
author_rank: Super Contributor
timestamp: January 19, 2019, 02:22:10 am
content: Modding a high voltage transformer to work at higher frequency:

author: Le_Bassiste
author_rank: Frequent Contributor
timestamp: January 19, 2019, 11:16:35 am
content: the kind of application the OP is talking about strongly reminds me of electrostatic loudspeakers. something like the audio transformer of the old QUAD ESL57 should do exactly what op is requesting.(no need to look out for spares, they are unobtanium)as mike points out, signal source is probably required to deliver double or triple of the requested output power, just to cope with parasitics. on top of that, core has to be pretty larger to handle low end frequencies as well. sizewise, looks like a 50VA / 50 Hz transformer to me. picture is ESL57 transformer bottom side with all the taps for bass and treble and some compensation networks. the whole shebam is put into a soft sheet-metal case and completely filled with wax for good reasons: bass stator voltage is 8 kVDC.

author: duak
author_rank: Super Contributor
timestamp: January 20, 2019, 07:07:21 pm
content: 7.5 KVp-p is 2.65 KV RMS. A 1 mA current draw implies 2.65 W, something than can be easily provided by a 8038 function generator chip and an audio amplifier. I think a few identical transformers with their low voltage windings connected in parallel and their secondaries connected in series could easy provide the voltage and current specified.I would first look for some vacuum tube audio amplifier power output transformers because they have lower distortion and a wider frequency response. If not, then mains power transformers, preferably with toroidal cores, will work but their voltage output at 40 Hz will have to be considered.Cheers,