ADE7858A Calculations for Rogowski Coil

Hello,

I want to use a PA3202NL Rogowski Coil from Pulse Electronics  with ADE7858A.

Datasheet: 416 µV/A @ 50Hz.

Can this Coil be used with ADE7858A?

How do i calculate the IGAIN and other needed registers for a Rogowski coil?

Thank you

  • 0
    •  Analog Employees 
    on Sep 2, 2016 5:18 PM

    Hi DavidX,

    The rogowski coil you show can certainly be used although there will be a few points to keep in mind.

    • The actual secondary output voltage, which for 50Hz is 416uV/A. This means that with the parts +/-500mV Peak input full-scale, the maximum current that can be measured without going above the full-scale inputs is about 850A.
    • The current channels on the ADE7858A have a PGA in front of the ADC, which allows a gain of up to 16x. Now with a gain of 16x, the maximum current that can be measured goes down to about 53A.
    • You will have to pick the rogowski coil and PGA gain setting that works best for your application.
    • Be sure to enable the Digital Integrator in the current channel data paths when using a rogowski coil.

    In terms of IGAIN, that only needs to be changed if you are trying to calibrate multiple meters so that they all have the same A/Code constant on the current channel. That is done the same way as if it was a CT as long as all the settings above have been setup. The idea of calibration is that with known inputs you can calculate constants for the meter in units of V/Code, A/Code, W/Codes, Wh/Code, etc. With these, the registers can be converted to real world values. A good resource is the Application Note for calibration, http://www.analog.com/media/en/technical-documentation/application-notes/AN-1076.pdf.

    Regards,

    Dlath

  • Thank you for your Answer!

    Do i need to calibrate  xPHCAL Registers if i use rogowski coils?

    The phase error is only 0.05 degree.

  • 0
    •  Analog Employees 
    on Sep 9, 2016 4:26 PM

    Hi DavidX,

    With a phase error of 0.05 degrees you shouldn't have to perform any phase calibration. Phase error has a larger effect when the power is at a non-unity power factor. If you want to double check, I would suggest looking at the error in your active and reactive at a PF = 0.5.

    In the end, if the phase error is 0.05 degrees then you should not have any problems and shouldn't need phase calibration.

    Regards,

    Dlath

  • Hi Dlath,

    just one more question,

    i see that there are new registers in 7878A that average xVRMS and xIRMS to

    IARMS_LRIP and VARMS_LRIP

    Can this registers be used for calibration or do i need to wait for a zero-crossing interrupt and read

    xVRMS / xIRMS?

    Thank you

    Kind regards

    David

  • 0
    •  Analog Employees 
    on Sep 12, 2016 9:33 PM

    Hi David,

    Those registers are good to use for calibration. It follows our other recommended method of reading the RMS with low ripple which is to average at least 50 readings for a 50Hz system over 1 second. This RMS_LRIP measurement is even better because it averages all 8192 readings over the second.

    Regards,

    Dlath