1kV transformer suggestion

[samkountz]

I'm having trouble finding a 10V to 1kV isolation transformer that's rated around 10VA. Wanted to see if you all had any suggestions.

 

[Nigel Goodwin]

I'm not surprised you're struggling, that's an incredibly unlikely transformer to find for sale, it would probably need to be specially made.

What's it for?.

 

[samkountz]

I'd like to increase a waveform from a Siglent SDG2042x function generator. The function generator output will be connected to a 10W power amp which would drive the transformer.

 

[Nigel Goodwin]

I'd like to increase a waveform from a Siglent SDG2042x function generator. The function generator output will be connected to a 10W power amp which would drive the transformer.

You're not going to find any such transformer, you'll either have to wind it yourself, or have it wound.

What frequency range are you looking for?, usual 50Hz or audio range?.

 

[samkountz]

Audio frequency up to 100kHz, though signal integrity isn't critical.

I'd consider chaining multiple transformer, eg 24-120 + 120-1k, but I'm not sure if that's advised.

 

[Nigel Goodwin]

Audio frequency up to 100kHz, though signal integrity isn't critical.

Well mains transformers are intended for use at 50/60Hz, and don't really perform well at higher frequencies - and even specific audio transformer don't usually go anywhere near 100KHz (100KHz is ferrite core country, not iron laminations).

There have been people in recent times though using small mains transformers as output transformers in single ended valve amplifiers, with reasonable success, but with the lower quality of valve amps a lack of treble probably isn't too much of a concern.

You've also got the problem of 1KV though, any 'off the shelf' transformers are likely to be only intended for mains voltages - but if you can get transformers intended to output 1KV from 120V they should be OK. You could certainly try two transformers in series, and see what happens.

 

[samkountz]

Great, thank you for your advice!

 

[JimB]

Well mains transformers are intended for use at 50/60Hz, and don't really perform well at higher frequencies - and even specific audio transformer don't usually go anywhere near 100KHz (100KHz is ferrite core country, not iron laminations).

This has a familiar ring to it...

Looking back a couple of months there were some discussions about measuring distortion on a mains supply and the frequency response of a transformer used for safety isolation.
At the time I did some simple frequency response tests on two small transformers, the results are reported here:

Testing AC Line Quality with an Oscilloscope - Generator power quality

Without reading through the entire thread, this looks like the lack of a ground. If you are using differential input to the scope, the source still has to have some kind of a ground reference or the noise will get though. Tie the safety ground and the neutral together and connect the scope...

www.electro-tech-online.com

With those results in mind, my first thoughts are that using a mains transformer up to 20 or 30kHz may be OK, but 100kHz would take some thinking about.
Maybe use two separate transformers, a nice chunky iron cored one up to say 20kHz, and a ferrite cored one up to 100kHz.

JimB

 

[ronsimpson]

10V to 1kV isolation transformer that's rated around 10VA
Audio frequency up to 100kHz

20hz to 100khz is a very wide range. A ratio of 100:1 is fine but 5000:1 is too far. At 20hz you need a large transformer and at 100k you need a small transformer.
When you say 10VA, I understand you have a 10 watt amplifier. What is the output current? How much power on the output? What are you driving?
Did you find a audio amplifier that will work to 100khz?

I have made transformers for 30khz to 120khz that output 1000V at very low current to drive CRT monitor focus grids.
I have made amplifiers that did DC to about 30khz at 1kV at very low current. At high frequencies they get hot. I can not get high voltage transistors any more but I may have some old ones.

More information will help.

 

[dr pepper]

Not really my field, however electrostatic speakers usually have a step up transformer in them, I think they are around that voltage, you might be able to get one as a spare part.
But dont expect 100kc though, around 25kc would be the max.