Please Help me

wrote:


But they want a transducer which can give us the required PLC input (4 to 20 mA) using a single CT.
Can the sample be DC? if so 3CT and a simple 6 diode rectifier. This will help take into account voltage sags on one or more legs vs. sampling a single leg.

I would suggest you look at SSAC (or even call and talk to an application engineer) http://www.ssac.com
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snipped-for-privacy@gmail.com wrote:

Does your PLC have spare control outputs? Perhaps you could have 3 CT's and a remote switch to "multiplex" the single analog input. You would have to write your program to syncronize the remote switch to follow whatever calculations/display you need to do.
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Joe Leikhim K4SAT
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if you dont have an ammetre, you can use 2 wattmetres and a voltmetre considering the load is balanced. if the load is unbalanced then one more wattmetre is required.] then,
(I phase) = (W) / ((sqrt 3)*(V line)*(power factor))
where W = sum of reading of 2 wattmetres V line = voltage measured ACROSS 2 lineS power factor = you've to find out else its usually = 0.8
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----------------------------

In other words you are suggesting use of two more costly (in general) meters and a voltmeter, along with a guess as to power factor, to replace an ammeter. Why?
In addition, the expression that you give will result in line current rather than phase current so it is in error. Please check your textbooks.
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Don Kelly snipped-for-privacy@shawcross.ca
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Wouldn't it be easier, less expensive, and more accurate to just buy an ammeter?
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Benjamin D Miller, PE
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