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ankur malviya
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Join Date: Aug 2012
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DC Sence Current Transformer Selection

08/24/2012 5:49 AM

Hi Friends,

Can any body tell me how to select CT for the measurement of DC current accurately, & with which parameter consideration.

Best Regard's

Ankur Malviya
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Pathfinder Tags: Current Transformer
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Tornado
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#1

Re: DC Sence Current Transformer Selection

08/24/2012 10:05 AM

Rather than a CT, use a low resistance shunt and a voltmeter.

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Joshi
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#2

Re: DC Sence Current Transformer Selection

08/24/2012 10:16 AM

How can you use a CT (current transformer) for measuring DC amps? Does a transformer work in DC circuits?
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NotUrOrdinaryJoe
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#3

Re: DC Sence Current Transformer Selection

08/24/2012 12:16 PM

There are a few Hall effect sensors that may read the DC component. A current transformer will not work because it will magnetize in the direction of the DC current flow in about 8 mSec.

For a CT to perform properly, you need to use it on alternating current. Specifically, it needs to be nearly the opposite polarity about half of the time or it will saturate in one direction and yield no signal.

Voltage across a small known value resistor (0.1 ohm?) is actually very accurate for calculating current as long as you are not heating it significantly.

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Joshi
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#4
In reply to #3

Re: DC Sense Current Transformer Selection

08/24/2012 12:44 PM

I agree wuth you.
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JRaef
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#5

Re: DC Sence Current Transformer Selection

08/24/2012 1:03 PM

There are indeed DC "CT"s that look just like AC CTs, but you have to accept the alternate meaning of "CT" to be Current Transducer.

http://www.veris.com/docs/app/vn38.pdf

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Joshi
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#6
In reply to #5

Re: DC Sense Current Transformer Selection

08/24/2012 1:13 PM

The OP's Tag says current Transformer.

Thank you for the explanation & the link.
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JRaef
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#7
In reply to #6

Re: DC Sense Current Transformer Selection

08/24/2012 7:27 PM

Oops, you are correct. My mistake...

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kvsridhar
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#8

Re: DC Sence Current Transformer Selection

08/25/2012 4:49 PM

Er.. "DC Current Transformer" seems an acceptable term, at least in the US Patent Office...

http://www.freepatentsonline.com/20120063055.pdf

Anyway, i have seen several massive DCCTs 180,000/5A DC in a caustic soda plant (which used electrolysis). Don't ask me how they work though, i never bothered to find out in detail. This was in 1972 at Kota, Rajasthan.

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#9
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Re: DC Sence Current Transformer Selection

08/25/2012 4:56 PM

Welcome to the U.S.! Are you visiting, or staying for a time?

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kvsridhar
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#10
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Re: DC Sence Current Transformer Selection

08/25/2012 8:14 PM

i came at the end of May, mainly to play with my new granddaughter Hope to leave by mid-Nov, staying a few days short of the full 6 months allowed. My fifth trip since '82. America has sure changed in many ways, more of it in a good way, from a foreigner's perspective. The one downside is how expensive everything has become....

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Tornado
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#11
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Re: DC Sence Current Transformer Selection

08/25/2012 9:16 PM

If there is any way that you could make it to Ketchikan (petrol > US$4), you will be a most welcomed guest! All love to your granddaughter and family.

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kvsridhar
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#12
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Re: DC Sence Current Transformer Selection

08/25/2012 9:37 PM

Wow... makes me feel very welcome, very warm. Thank you, friend ! Alas, i am not allowed to drive here (by my son and d-i-l, not the US DMV)so, i have to depend on them for even going a couple of miles But let me take a raincheck on it, i hope to come again sometime...here is a picture of my angel....

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electricalexpert65
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#13
In reply to #12

Re: DC Sence Current Transformer Selection

08/29/2012 9:57 AM

KVS! Your lil' angel is so cute! My blessings to her!
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kvsridhar
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#14
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Re: DC Sence Current Transformer Selection

08/29/2012 10:30 AM

Thanks EE65 ! i will surely convey your message to the proud parents ....

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