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Synthesizing a 16Arms Sine wave

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cupoftea

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Hi,
We are making a device which switches up to 16A rms in the 240VAC mains into a device. It also needs to measure the 16A. We measure it with a Current transformer in mains live.
When we test the equipment, we currently load it up with a 16A load, so that we can see that it measures it properly. -But this means us dissipating 3.8kW in a dummy load during production test......not good.

Therefore, we wish to simply synthesize a 16Arms sine wave and shovel it through the current transformer, of course doing this while the live conductor around which the current transformer torroid sits is energized....it needs to be in phase with the mains voltage.
....We believe we can do this using a kind_of Class D amplifier stage with a 60V isolated DC input power supply as attached. it feeds into a 30V battery, but of course, there is no overall load in this as it receives AC current.
What do you think of this?
By the way, the control loop hasnt yet been completed in the attached.
(LTspice sim and pdf schem attached)
 

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  • sine wave current 16A.pdf
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  • Sine wave current _16Arms.zip
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betwixt

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If you have confidence in the CT itself, and lets face it, there isn't much that can go wrong with one, why not just synthesize the secondary signal. You can probably do that with nothing more than a normal low voltage transformer running from the AC supply so you know it is in phase. If you need to test the CT itself, do it at low current just to check it works.

Brian.
 

cupoftea

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Thanks, but i am thinking now of a bridge setup....switch one diagonal pair for 10ms, then the other, and make the current half sinusoid in each direction.....we do need the full 16Arms to be synthesized malheuresement.

...ive managed to do this with a boost from 30v to 60v, but its just a train of half sines, not bipolar.....the 60v could be bucked back to the 30v so "no energy" was used.
 

Easy peasy

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a 230 to 10V transformer rated at 16A rms out would seen to be the quickest and easiest solution, for even lower power, add a variac and short the current loop - bringing up the variac just enough so that 16A is flowing int he short ...
 
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