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umery2k75
Joined: 19 Apr 2006
Posts: 378
Helped: 24
Location: Pakistan
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 02 Nov 2009 10:06 OPAMP Current Transformer logic |
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| I have traced a schematic of a circuit. It's faulty and it doesn't operate.Now this circuit can't be repaired, but I want to learn how it's designed. It's MCU has gone faulty. Any how. I will post the traced schematic today. I don't understand in one part. There was a CT, reading AC current then from that, it goes to a bridge with 100 Hz SINE frequency, because the line frequency is 50Hz/220VAC then it was filtered out by a capactitor and then it was fed into an integrator. I don't understand why he was integrating the current.The circuit was monitoring the current I think. By varying the current, DC level gets shift of a capacitor, then this DC level was fed into an integrator.
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FvM
Joined: 22 Jan 2008
Posts: 5161
Helped: 767
Location: Bochum, Germany
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02 Nov 2009 10:24 OPAMP Current Transformer logic |
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| Is it a true current transformer or a di/dt pickup(Rogowski) coil?
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umery2k75
Joined: 19 Apr 2006
Posts: 378
Helped: 24
Location: Pakistan
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02 Nov 2009 11:13 Re: OPAMP Current Transformer logic |
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It's a true Current Transformer. I don't remember the name, it's written at home. I will write the name of CT,when I come home.
Added after 9 minutes:
I'm confused. I think the RED Current Transformer that it may seem to me on the PCB, might be of Air Core Transformer.I read about Rogowski coil, it says that it can measure AC and DC both current and it has Air core. You have given me a HINT. I am calling my friend to study about Rogowski CT and study more about the actual CT circuit. I will be more prepare in my next post. Thankyou FVM  You are one of the best man around in here.
Added after 1 minutes:
I'm confused, I'm not sure whether it's TRUE Current Transformer or Rogowski Coil.
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umery2k75
Joined: 19 Apr 2006
Posts: 378
Helped: 24
Location: Pakistan
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02 Nov 2009 17:43 Re: OPAMP Current Transformer logic |
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This is the website of the current transformer.
http://www.sirio-ic.it/products/pr_08.htm
When I looked at the datasheet, it appeared as it it's not the Rogowski type current transformer.It's ferrite core. I see the below website, I didn't get differential wave form as shown in the figure, when I put my oscilloscope probe on to it to measure the output of the CT.
http://www.pemuk.com/howitworks.html
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FvM
Joined: 22 Jan 2008
Posts: 5161
Helped: 767
Location: Bochum, Germany
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02 Nov 2009 19:40 OPAMP Current Transformer logic |
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A rogowski coil is always an air coil without a core. It's supported e.g. without an external integrator by the ADI energy measurement chips and
generally a good choice for accurate measurement of high frequency AC currents.
But you have apparently a usual current transformer. So what's special with the circuit?
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