CT or Shunt for Electricity Meters ?!

[hm_fa_da]

Dear Friends,

for single phase KWH meter, i can use both CT and Shunt, which is more accurate ?!

and do you know what exactly 5(100)A mean ?!
i saw it means max 100A, but what does that 5A mean then when it supports up to 100A ?!!

Thanks & Best Regards

 

[KlausST]

Hi,

I'd say a shunt is more accurate. But with it's low signal voltage you need to take care with amplifying the signal.
A wrong designed amplifier or a bad layout could easily make the overall performance worse than the CT.

5 (100)... For sure you could find reliable information in the internet.
I guess the 5A is for continous RMS current, the 100 is the peak current. But i'm not sure..

Klaus

 

[red_alert]

100(5)A means 100A primary (input/measured) current and 5A (full scale) output current.

If you only need to measure AC currents (and you need galvanic isolation, too) a CT it's a better option, as it only requires a single external burden resistor (and maybe a simple rectifying/filtering circuit) to feed the output signal to your measuring circuit.

 

[KlausST]

Hi,

(and maybe a simple rectifying/filtering circuit) to feed the output signal to your measuring circuit.

Rectifying and filtering .. I don't think it is possible for a kWh meter, because you need phase shift information.

Klaus

 

[red_alert]

Of course, I was talking about CT use in general terms. One could condition its output for specific measurements (peak, rms, average, phase shift).