Author Topic: maximum burden resistor across CT  (Read 1908 times)

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Offline embedded.world@aol.com

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maximum burden resistor across CT
« on: July 04, 2014, 09:53:08 am »
How to calcluate maximum burden resistance across CT.
I have CT with 60Hz frequency.

I want to generate 2.5V across it to measure it across adc.

How to calculate what could be maximum & minmum values of burden resistor for proper operation i.e without saturating the core.
 

Offline rob77

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Re: maximum burden resistor across CT
« Reply #1 on: July 04, 2014, 10:10:28 am »
sorry i don't have my crystal ball with me , therefore i can't guess the missing details accurately  to provide you a meaningful answer :D
 

Offline T3sl4co1l

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Re: maximum burden resistor across CT
« Reply #2 on: July 04, 2014, 11:12:18 am »
Too large a resistance and the winding inductance reduces gain and causes phase shift.  The cutoff is: Rb <= 2*pi*F*Ls*/err, for err ~= 0.  Example: err = 0.01 (a 1% gain error).

This requires knowing the winding inductance, which is usually provided.  Sometimes, manufacturers will give a recommended maximum resistance, directly.

Tim
Seven Transistor Labs, LLC
Electronic design, from concept to prototype.
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