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Current Transformer DC

03/21/2022 1:07 AM

Just got a 10ADC Current Transformer which I would like to reduce down to 2ADC Current Transformer or thereabouts.

If I put another winding through the current transformer I would reduce the ratting to 5ADC. And then if I put an additional winding through the current transformer the ratting would be reduced to 2.5ADC

Just wanted to ensure that I am thinking of the logic the correct way, your responses are appreciated

Cheers Joe

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#1

Re: Current Transformer DC

03/21/2022 2:05 AM
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#5
In reply to #1

Re: Current Transformer DC

03/22/2022 1:47 PM

Good day.

Regarding with same issue, beside to use CTs I am trying to make Voltage measurement but non-intrusive.

There is any device that could make it ?

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#7
In reply to #5

Re: Current Transformer DC

03/22/2022 9:11 PM

So you only want to measure voltage, not current? Now do you just want to detect the presence of voltage, or the actual voltage?

DC detection works best with actual contact, AC involves measuring the field produced...both require contact to measure the actual voltage...afaik

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#8
In reply to #7

Re: Current Transformer DC

03/23/2022 12:29 AM

No, I want to measure current through a Hall Effect Current Transformer

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#9
In reply to #8

Re: Current Transformer DC

03/23/2022 2:45 AM

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#2

Re: Current Transformer DC

03/21/2022 8:22 AM

I'm assuming you are referring to a current sensor.

DC current transformers measure the current through a wire by measuring the flux caused by that current.

"CR5200 DC Current Transducers are designed to provide a DC signal which is proportional to a sensed DC current. These devices are designed for direct current only, targeting them towards general and daily applications. The ranges 2 to 10 Amp utilize an advanced Magnetic Modulator technology and the ranges 20 amps and above utilize Hall Effect Technology."

https://www.crmagnetics.com/dc-current-transducers

Back to your question: If you pass the wire through twice, a 5 amp current will register as 10 amps. If you pass it through 3 times, a 3 1/3 amp current (not 2.5) will register as 10 amps, and so on.

1 pass, 10A reads 10A

2 passes, 5A reads 10A

3 passes, 3.33A reads 10A

4 passes, 2.5A reads 10A

5 passes, 2A reads 10A

etc.

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#3

Re: Current Transformer DC

03/21/2022 8:31 AM

Actually, I think you are correct in principle, but I am a little puzzled by it being a DC current transformer, since transformers don't work on DC. It must be some other sort of transducer for DC than the classic wound transformer.

That said, I tend to think of it from the perspective of the CT ratio. If it is 100:1, for example, and I want 50:1, then I would wrap an extra turn of the primary through the CT. Then it gives me 2x the current in the primary (50A x 2 wraps), and would result in 1A in the secondary - Voila! A 50:1 CT!

So if your 10ADC CT works the way an AC current transformer works, then you need FOUR wraps through the CT. This gives you 10A/4 = 2.5A in your primary winding for full scale secondary.

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#6
In reply to #3

Re: Current Transformer DC

03/22/2022 2:24 PM

DC Current transformers use Hall Effect I think

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#4

Re: Current Transformer DC

03/22/2022 6:33 AM

Your logical thinking seems to be correct, with the exception that transformers are supposed to be an AC device only..

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#10

Re: Current Transformer DC

03/24/2022 10:10 AM

The total package...

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#11

Re: Current Transformer DC

03/24/2022 10:07 PM

The consept is correct, it is actually a common practice in order to increase the sensitivity of a current transformer BUT there are caveats. A single winding is defined as a 360 deg turn followed by sharp 90 deg bend of the leads of the current bearing wire so that get out of the field being parallel and cancel out and only that single turn affects the core. In a single turn the geometry counts. I'm trying to say that you cannot avoid some kind of calibration comparing with another working current meter in series to get meaningfull and repeatable results. For those that will argue against this, just test a clamp meter with an exact whole turn over the jaws and compare that with the reading when the wire is just passing straight through. The readings will be near 2:1 S.M.

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Anonymous Poster (1); Joe Sparky (2); PeterT (1); Rixter (1); SolarEagle (4); sqyuma (1); vsar (1)

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