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ADE9078 Schematic Design Review

Product Number: ADE9078


I am using the ADE9078 for 3Phase current and voltage measurements
and I have some questions about the design 


1- In my design, I use the Neutral as AGND, and I connect the ADE9078 direct to the MCU without using any Isolation IC , is this will cause a problem in my design, and how I can solve that? 

2- How I can calculate the burden resister If I want to use a 5000:1 or 1000:1 CT ratio, and a 100A maximum   ? 
 

  • The recommendation for pin 17 and18 is to GND the N/C on those pins.

    I do not recommend not using isolation. If you have any communication ports that are nto isolated and someone  swapped line and neutral you will have the line voltage on your system ground. 

    As for the CT 

    The max RMS input is .707 

    burden =.707 /  (100 / CT turns ration )

    burden = .707 / (100/5000) =  35.35 ohms   / 2 for differential burden

    this will make the 100A full-scale on the ADC. You may need to measure surge currents so you may want to use 200A or 300A depending on surge requirement. 

    Dave

  • Thanks, Dave

    I Isolated the signals and power supply

    - I use ISO7241CDWR to Isolate the SPI signals
    - and I use optocouplers to Isolate the other signals like IRQ0, IRQ1, CF1, CF2, CF3, and CF4, I use optocouplers because of the cost-wise, so If you find this Will case problems please inform me and I will change the design

    For the Isolation Power supply, I decided to use two different methods
    1- using  220v to 5v module which will supply just ADE9078
    2- I found another solution in this application note
    https://www.analog.com/media/en/technical-documentation/application-notes/AN559.pdf
    which they use a half-wave rectifier

    so I decide to use both of these methods to test them and I will switch between them using a jumper wire