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ade7758

Category: Hardware
Product Number: ADE7758

Hi

I have recently been experimenting the ADE7758 energy measuring IC for a work project, I have managed to get it operating to the point i can read voltage and current in a star configuration and convert the values to useful figures using an atmega328p but I am struggling on a couple of points trying to move forward.

-I am looking to obtain a power reading from the meter but I am unsure whether or not this takes into account the power factor in the system, if not I was wondering how i would get that variable.

-My second issue is understanding how i would setup up the meters connection for a  delta system

Thank you for your time

John

  • The part calculates power/energy on a sample-by-sample basis. So, the power calculation is V x I x pf. the pf is accounted for, but you do need to do phase calibration to correct for any sensor phase shift.

    in a delta configuration phase B is tied to neutral. Your voltage rms measurements will be phase to phase B. 

    This is a non Blondel configuration and individual phase power/energies are not correct but if you add them up the total system power is. 

    https://www.analog.com/media/en/technical-documentation/application-notes/an-639.pdf

    look at the 3-phase section for more information.

    Dave

  • Hi  

    Thank you for the reply, that's cleared up a lot of confusion on my part Slight smile.

    Just stuck on changing the CONSEL value now in the COMPMODE, i can read the default value 0x1C that is given on the data sheet, but unsure as to how to change it as i can write to the register but it looks like it only requires the modification of bit 0 and 1 of the register. 

    Was wondering if you could offer any advice on that matter? (working with Arduino IDE 2 and Arduino UNO).

    Thank you for your time

    John

  • read the register and modify the bits you need then write back or just write a new value that you need based on the datasheet. 

    Dave

  • Hi Dave

    Thank you for the reply once again.

    Was wondering if you could just confirm if my understanding is right (first time dealing with IC registers).

    So when i read the COMPMODE register i receive 28 decimal, which is 0x1c in Hex the (default value stated on the datasheet) and 11100 in binary, so from the right the first two bits represent the CONSEL bits. So as they are both set to zero it is already in a 3 wire delta setting (as per table 10 & 11 of the data sheet)? 

    Thank you again for your time and help Slight smile

    John

  • This table is correct  00 is 4wire wye and 3 wire delta. in delta phase b would be tied to gnd and power would be Vab * IA and Vcb * IA

    01 and 1 are also for delta 4 wire and 3wire with 3 current sensors.

    by default the part should come up in wye config 00 from table below which is also delta 

  • Hi Dave

    Was wondering if i could call upon your expertise again Slight smile

    Carried out a test on a machine we have the other day, initially tested it with a calibrated fluke energy meter to get the actual values to check against, then tested the ADE7758 circuit i have and the values for W VAR VA didn't quite add up.

     I was wondering if my hardware configuration was the cause.

    So as it stands my circuit is set up as per the recommended test circuit in the ADE7758 datasheet (Using CT's)

    For the CT side i have a burden resistor of 10 ohms which gives me the 0.5V range on those inputs. However the CT's i have produce a maximum output of 333mV rms, so would i be correct in assuming the burden resistor would be redundant in that case?

    Also as i was doing the 3 wire delta configuration i replaced the 1M ohm resistors on the voltage inputs with 2M ohms to keep the peak voltage below the 0.5V allowed on the inputs.

    Would any of this cause the reading to be wrong?

    Thank you once more

    John 

  • You can change the resistors that is fine, but this will also change you watt var and va per lsb constants. 

    Can you supply some data (raw from register) of your readings and your input signals at the adc's 

    Have you verified the WYE setup works?

    Dave

  • Hi Dave

    Thanks once more for your help

    To now I have not tested the ADE7758 on a wye configure piece of equipment, as I am predominantly dealing with delta configured machines.

    I have ran another run of tests this morning (unfortunately i disabled the part of the code that retrieves the Watt value, but have VA and VAR)

    Also I have used our Fluke energy meter to obtain what the apparent and reactive power should be.

    Please see link to my Github repository for the test data  

    github.com/.../ADE 7758 TEST DATA.pdf

    John

  • Hi Dave slight correction, I have not tested the power, VA and VAR measurements on a star configuration, only the voltage and current.