ADE9000/9078 Negative power

Hello

We are working on a device that measures currents, voltages, power and energy on all three phases. For prototype series we are using ADE9000 and for the release ADE9078.

We have observed the issue with sign of the power measurement on phase A (it was not tested on other phases).

Devices with ADE9000 and ADE9078 behaves similar.

For the test, all the gains are set to 1:

AIGAIN = 0

AVGAIN = 0

APGAIN = 0

The device was loaded with heater that has roughly 2kW. The results were:

AVRMS = 17446358 (roughly 210 V)

AIRMS = 9587710 (roughly 8 A)

ANGL_VA_IA = 10085 (354 degrees)

AWATT = -1245912 (0xFFECFD28) (around 1.7 kW if raw value is multiplied by -1)

When current gain was changed to -1 (AIGAIN = 0xF0000000) following results were observed:

AVRMS = 17856969

AIRMS = 9807378

ANGL_VA_IA = 81 (2 degrees)

AWATT = 1304039 (around 1.7 kW;  -1 multiplication in the conversion was removed)

 

Could you please help us understand:

Why are we getting negative power when angle difference between voltage and current is -5 degrees.

Why after switching to -1 gain for current we don’t get around 180 degrees of angle difference between voltage.

 

Additional notes:

Voltages are measured through voltage divider 20 Meg – 24 KOhm.

Currents are measured using ACS772LCB-050B-PFF-T Hall effect sensors

Input circuit - voltage and current

Conditionig of the current sensor output

All the inputs are referenced to GND (Protective earth)

  • +1
    •  Analog Employees 
    on Sep 1, 2021 2:33 PM

    Hi Are you doing phase calibration ? If yes, What do you write to phase cal registers? 

    Why such a large divider?  I don't see any filtering on the adc inputs. We typically use a simple RC.   1K  and  22nf. 

    The voltage channel input impedance is 185Kohm this is in parallel to 24K. This ratio is to low and may cause performance issues.  1K and 185K input is a better ration for performance over temp. 

    But if it works and meets your requirements you will be ok. 

    Now  for the angle :

    for the ade9000     angle = reg * 0.017578125 for 50 HZ  angle = reg * 0.02109375 for 60 HZ

    for the ade9078     angle = reg * 0.017578125*2 for 50 HZ  angle = reg * 0.02109375 * 2 for 60 HZ

    I think you are using an ade9078  correction for an ade9000 part.

    9000 9078
    50 0.017578 0.035156 angle / lsb
    60 0.021094 0.042188 angle/lsb
    81 1.423828 50hz 2.847656 deg
    1.708594 60hz 3.417188 deg
    10085 177.2754 50hz 354.5508 deg
    212.7305 60hz 425.4609 deg

    angle/lsb =  line freq / (crystal/24) * 360     crystal is 24.576 MHz  for ade9000 and 12.288Mhz for ADE9078

    time base for the angle measurement is different for ade 9000 and ade9078

    ADE9078

    ADE9000 

    Please verify if this is the issue

  • Thank you, Dave, on a quick reply. You are right, I have made a mistake of assuming that conversion factors for angles were close enough between devices as in case of voltages and currents.

    With correct conversion factors it’s as expected.

    As for other remarks, we are aware of the issues in the current design. For now, the measured values are precise enough for our needs.

    Thank you again and best regards

    Ugljesa