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30A precision current source
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Zero999:
How about a Howland current pump driving a transformer?

A bipolar power supply is idea, but it can be bridged to work from a single supply.

This design is only 3A, but add a 10:1 transformer and you have 30A on the secondary, albeit at a lower maximum voltage, which I presume won't matter has it's only driving a current transformer.

The voltage between the feedback and output nodes follows the voltage on the in node. Because R7 and R8 form a potential divider, the voltage on R5 and R6 is double the input voltage.

Ensure:
R1 = R3
R2 = R4
R5 = R6

R1 & R2 configure the gain.
R5 & R6 double as emitter ballast resistors and current sensing resistors.
X1 can be replaced with a resistor to reduce the output current.
coromonadalix:
gonna sound stupid   but this schem is an audio amp ?? 

Adding a transformer wont help at all,  you have core losses, hysteresis  etc ...  you're creating problems and affect any precision you want ??

You want 30 amps at 50 hz, but at what voltages ??  1v rms or pk to pk ?


there is an really powerfull op amp, an lm12

http://www.ti.com/lit/an/snoa718/snoa718.pdf


I saw your howlad pump principles
https://www.allaboutcircuits.com/technical-articles/the-howland-current-pump/
Zero999:

--- Quote from: coromonadalix on April 06, 2019, 07:27:18 pm ---gonna sound stupid   but this schem is an audio amp ?? 
--- End quote ---
Yes, it is the same topology as an audio amplifier, except the output is constant current, rather than voltage.


--- Quote ---Adding a transformer wont help at all,  you have core losses, hysteresis  etc ...  you're creating problems and affect any precision you want ??
--- End quote ---
Please explain how?

Transformers are commonly used for measuring current and as long as they're not overloaded, don't affect the accuracy at all. I've recently used one in a current measuring application and found the secondary current was within 1% of the primary, which was within the bounds of accuracy of my oscilloscope. The usual configuration is a one turn primary with many on the secondary, to reduce the current so it can be sensed using a much higher value resistor (known as the burden) than would otherwise be practical, but it will work in reverse: more turns on the primary, than secondar. To increase the knee voltage, the primary can be more than one turn, although I think that will increase the phase shift, but it's probably a non-issue in this application.
https://en.wikipedia.org/wiki/Current_transformer
ali_asadzadeh:
Thanks all for your suggestions and hints.



--- Quote ---It's clearly not a bipolar current source (it's a simple current sink). I'm guessing you implied you want a bipolar source (and several here have understood so, probably because of your 'DC bias' remark) whereas I don't see it clearly stated in your post unless I missed something. With a 0-3.3V input sine signal, you'll just get a current sink between Imin (won't be 0, there will be a significant offset) and 3.3/Rshunt basically. That could be what you wanted after all. Unclear. Also, with 5V supply for your DUT, make sure you'll have enough headroom - we don't know anything about your DUT.
--- End quote ---

As I mentioned the DUT is a simple wire wrapping 1 turn inside a CT.



--- Quote ---No the circuit will not generate an AC current, without a DC bias.

What's the frequency range?

What's the maximum output voltage, at 30A?

If space isn't limited and the output voltage only needs to be 1V or so, then how about using a transformer to step-up the current, whist reducing the voltage?

1mA to 30A is a huge dynamic range. Your circuit will need multiple different range settings to give a decent level of accuracy.
--- End quote ---

The frequency range is from 40Hz to 400Hz, the maximum open output voltage is not important, the lower the better, because we have less dissipation.


Here Came something completely different to my mind! I can buy dirt cheap 5V 40A power supplies, something like this,

Also for the DAC, I decided to switch to an audio codec part, with 24Bit resolution (CS4344), This time the output is bidirectional, also I have managed to use a current sense IC instead of shunt resistor,
Any Idea's about this new design?




beanflying:
There is a series of commercial products available for what your spec is. Search for Transconductance Amplifiers or Current Calibrators should get you some hits.

eBay auction: #113702013768 Manual and Schematics Description here https://valhallascientific.com/wp-content/uploads/2018/09/2555A_Manual.pdf
Circuit Diagram and description of the 10A Cousin here https://valhallascientific.com/wp-content/uploads/2018/09/2500EP_Manual.pdf


Or there is several Fluke offerings designed to be run in conjunction with their AC Calibrators.
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