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### Author Topic: need help with volts and amps  (Read 12440 times)

#### Grone

• Newbie
• Posts: 5
##### need help with volts and amps
« on: August 22, 2012, 02:02:09 PM »
Hello,

maybe this is a 'stupid' question...
if I have around 2000 volts with only a few milliamps, can i convert it to 12 volts and at least 1 amp?

Thank you

#### Groundloop

• TPU-Elite
• Hero Member
• Posts: 1736
##### Re: need help with volts and amps
« Reply #1 on: August 22, 2012, 02:34:13 PM »
Hello,

maybe this is a 'stupid' question...
if I have around 2000 volts with only a few milliamps, can i convert it to 12 volts and at least 1 amp?

Thank you

Hi Grone,

Print out this chart and tape it on your lab area wall.
http://cdpropowercords.files.wordpress.com/2011/01/ohms.jpg

If you know the exsakt voltage and amperage of your input then you can use Ohms law
to calculate what output you will get. If you have approx. 2000 Volt AC as you input,
then you can use a micro wave transformer in reverse to get a low voltage (and higher
amperage.)

Groundloop.

#### fritz

• Sr. Member
• Posts: 424
##### Re: need help with volts and amps
« Reply #2 on: August 22, 2012, 02:43:51 PM »
if I have around 2000 volts with only a few milliamps, can i convert it to 12 volts and at least 1 amp?

Hi,

If you want 12V@1Amp we talk about a Power of P=UxI = 12V x 1 Amp = 12 Watts

If our source Voltage is 2000 V, the needed source current would be > I = P/U = 12W / 2000V = 6mA, or even more
depending on the efficiency of the converter.

For various technical  voltage/current situations - there are optimized converters.
Conversion from 2000V DC down to 12 V is a very unusual conversion - so there are no simple out-of-the-box approaches.
Typical semiconductors, transistors, fets used for switching supplies can handle maximum voltage of 600V, state-of the art uptto 1500V,  2000V ist typically above.

If we were talking about 2000V and _energy supply_ with lots of amps - there are thyristor modules which can chop your 2000V into AC - and the voltage could be stepped down with a transformer.

With just a very little current consumed - I have no simple idea at hand.

A basic principle is that the efficiency of the conversion decreases with the voltage span needed.

Making high voltage out of low voltage is even a very simple thing using a flyback transformer.

There ar 3 concepts : transformers (need ac)
magentic switch mode (using rf transformer or flyback)
charge pumps (using switched capacitors)

All 3 concepts need ac or a way to switch the dc current making a pulsed one out of it.
Having more than 600V - we would need a series of fets or transistors - to achieve the high voltage.
Then you would need a transformer which handles the 2000 - to 12 volt conversion - maybe in your case a series of
2 converters would be the solution.

Having conversion 1 from 2000V DC down to 240VAC,
and a second conversion using traditional power supply from 240 downto 12.

What I recall there are 2kV power lines and transformers - but not for 12W.

- conclusion: technically not impossible, but difficult because no standard circuits/schematics/components available.
probably difficult to achieve high efficiency.

#### Grone

• Newbie
• Posts: 5
##### Re: need help with volts and amps
« Reply #3 on: August 22, 2012, 02:44:56 PM »
Thanks a lot!

#### Grone

• Newbie
• Posts: 5
##### Re: need help with volts and amps
« Reply #4 on: August 22, 2012, 06:21:51 PM »
Hi Groundloop

I have around 2000 volts DC (20 milliamps) , can I use the microwave transformer with some oscillator?

for me it is also ok to have AC as the final output (up to 50 V)

Thanks

Hi Grone,

Print out this chart and tape it on your lab area wall.
http://cdpropowercords.files.wordpress.com/2011/01/ohms.jpg

If you know the exsakt voltage and amperage of your input then you can use Ohms law
to calculate what output you will get. If you have approx. 2000 Volt AC as you input,
then you can use a micro wave transformer in reverse to get a low voltage (and higher
amperage.)

Groundloop.

#### Groundloop

• TPU-Elite
• Hero Member
• Posts: 1736
##### Re: need help with volts and amps
« Reply #5 on: August 22, 2012, 10:42:31 PM »
Hi Groundloop

I have around 2000 volts DC (20 milliamps) , can I use the microwave transformer with some oscillator?

for me it is also ok to have AC as the final output (up to 50 V)

Thanks

Grone,

If you can find a transistor (MOSFET) that can handle 2000 Volt, then it is possible
to make a voltage downconverter. I'm currently on vacation with very limited Internet
connection but I will look into your problem sometime later on.

Groundloop.

#### TinselKoala

• Hero Member
• Posts: 13958
##### Re: need help with volts and amps
« Reply #6 on: August 23, 2012, 04:27:15 AM »
You need an "inverse Marx bank" or C-W generator. The way to do it is to take a bunch of individual capacitors.... how many? 2000/12 many.

Put these in series and charge up the whole stack. Then disconnect them and put them in parallel and use that to charge up another cap of greater capacity but lower (24 ) voltage. Then run your load off of the 12 volts on this capacitor.

You may need to figure out how to make the switch from series to parallel for your cap bank. I don't know how to do it electronically but it can be done mechanically with a clever arrangement of contacts and levers.

#### fritz

• Sr. Member
• Posts: 424
##### Re: need help with volts and amps
« Reply #7 on: August 23, 2012, 11:46:24 AM »
Even an unloaded microwave transformer operated in reverse would need significant magnetizing current which would lead in combination with a HV H-bridge to significant losses / poor efficiency if just 12Watt dissipated.
For a supply with few hundred watts (what this transformer is designed for) - this would be an appropriate approach.

A marx bank is somewhat the high voltage sister of a chargepump supply.
To protect the capacitors from overvoltage, a marxbank is using resistors - which impacts the efficiency.
Anyway, you would need perfectly isolating switching stages.

So I still think there is at least a two-step approach feasible - winding your own HV coils - and designing some HV-Switches (stacked up mosfet or transistor ladders)

rgds.

#### Grone

• Newbie
• Posts: 5
##### Re: need help with volts and amps
« Reply #8 on: August 24, 2012, 01:45:37 PM »
Thanks!

#### Groundloop

• TPU-Elite
• Hero Member
• Posts: 1736
##### Re: need help with volts and amps
« Reply #9 on: September 02, 2012, 05:17:28 PM »
Grone,

Attached is a circuit that MIGHT work for you. This circuit uses a transient protector as a spark gap
and will switch on at approx. 1600 Volt DC and off again at approx. 300 Volt DC. (+/-20%)
The 2000 Volt DC input will charge up the four series capacitors, and when the voltage is
high enough, then the transient protector will discharge the capacitors into the transformer primary.
The input resistor is a current limiter and will ensure that the capacitors will discharge to a low
enough voltage so that the transient protector will switch off again. And the cycle repeats.
The Ferrite transformer must be home made. See drawing for winding ratio. Be careful when
operating the circuit at 2000 Volt. The capacitor charge can do serious damage to your body!
If you need exactly 12 VDC at the output then you can use a 7812 voltage regulator.

Groundloop.

#### poynt99

• TPU-Elite
• Hero Member
• Posts: 3582
##### Re: need help with volts and amps
« Reply #10 on: September 02, 2012, 05:42:57 PM »
GL,

Have you built and tested this?

Does the 100k resistor get warm?

#### Groundloop

• TPU-Elite
• Hero Member
• Posts: 1736
##### Re: need help with volts and amps
« Reply #11 on: September 02, 2012, 06:05:20 PM »
GL,

Have you built and tested this?

Does the 100k resistor get warm?

.99

No, I have not built and tested this circuit. But I see no reason for it not to work.
If the resistor gets warm then he must use a higher wattage resistor. The resistor
value (Ohm) may also be changed in a practical circuit build. This was the simplest
circuit I could think of, avoiding transistors, mosfets, thyristors etc. At 2000 Volt DC
a very narrow band spark gap may also work, thus eliminating the transient protector.
This circuit has so few components that it may be worth a try.

GL.

#### Grone

• Newbie
• Posts: 5
##### Re: need help with volts and amps
« Reply #12 on: September 03, 2012, 12:17:28 PM »
Great! Many thanks GL !!!

will put the circuit together and give it a try!!