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I am working on an experiment and need a high voltage (10 kV to 12 kV) low frequency (5 Hz to 15 Hz) AC power source. The current can be 1 mA to 3 mA.

How do I design this?

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closed as too broad by pipe, Leon Heller, DoxyLover, Dmitry Grigoryev, Voltage Spike Mar 15 '17 at 18:09

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  • \$\begingroup\$ As it stands, your question is far too broad and doesn't show any effort you've made already \$\endgroup\$ – Artūras Jonkus Mar 15 '17 at 8:15
  • \$\begingroup\$ The most flexible solution would be a signal generator, audio power amplifier, with a step up transformer. The mA requirement means that the power amplifier can be quite reasonable specs. The 5Hz bottom frequency means that your transformer will need a lot of iron to avoid saturation, and a lot of turns to get the voltage, but it is do-able. \$\endgroup\$ – Neil_UK Mar 15 '17 at 9:04
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The maximum flux density in a transformer is related to the voltage-time integral. This means that you can use normal 50 Hz or 60 Hz components if you derate the voltage 5/50 or 5/60 times.

Lets say you can get a 50 Hz 120 kV to 120 V voltage transformer somewhere. You can then use it at 5 Hz as a 12 V to 12 kV step-up transformer without saturating the core.

This will also give you an idea how to use 50 Hz designs as long as you derate in accordance with \$\int^{{1\over 2}cycle} v(t) dt\$.

(Remember that for a 1000 x step-up you will need 10 A to 30 A :-)

You can also look at cycloconverter designs.

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A straight transformer will be difficult thanks to the required primary inductance, as another answer says, you can do it by massively de-rating 50-60Hz components which are already rather large.

I think you may have to treat this as a Class D amplifier so that the HV generation takes place at high frequency, possibly with a flyback topology for voltage multiplication - possibly using a Class D amplifier as a basis. As an alternative to a HV transformer, it can drive an ignition coil (or something very similar) to generate high voltage spikes on the secondary, which you then rectify and filter with a HV rectifier and an RC filter.

Not sure how you make this bipolar : you may need a separate ignition coil and HV rectifier (with the opposite polarity, connected to the same RC filter) to generate -ve output voltages. Alternatively, we don't know if the application would permit bridge drive, which may make life simpler.

Using high frequency switching allows small inductors, and only the secondaries, rectifiers and output filter need to operate at high voltage. A voltage divider, say 1000:1, can provide feedback to guarantee linearity.

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    \$\begingroup\$ You need AC output so rectifiers will not work, you need switching and that remains a challenge at 12 kV. (Ignition coils are not practical as they are designed to fly back at high frequency. :-) \$\endgroup\$ – skvery Mar 15 '17 at 10:54
  • \$\begingroup\$ @skvery You're missing my point, perhaps I wasn't clear. One rectifier won't work, two can - one for each half cycle, each energised by its own flyback coil or high ratio transformer. You're switching at relatively low voltage, not 12kv. \$\endgroup\$ – Brian Drummond Mar 15 '17 at 11:06
  • \$\begingroup\$ Simulate a proof of concept please, as a challenge! (See the cycloconverter link in my answer. :-) \$\endgroup\$ – skvery Mar 15 '17 at 11:10
  • \$\begingroup\$ How much is it worth? \$\endgroup\$ – Brian Drummond Mar 15 '17 at 11:11

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