i have used ade7880 ic for three phase measurement. in my case voltage and current are perfect through the range of 1v to 600v and 0.3A to 20A.
i have problem with power factor, i calibrate power factor using APHCAL register at 0.1(low power factor) at 250V , 10A
now when i change voltage from 250v to 550v ,power factor get changed and this change in power factor disturb the total active power (awatt).
After calibration if i change only power factor (voltage and current same) then it is accurate through out the range 0.1 to 0.9999.
if there any calibration issue than please describe power factor calibration process in detail. i have read application note AN-1171 in detail and followed all step mentioned in it. i am using calibration process using energy registers.
one other issue is that as per datasheet of ade7880 , APF register is 16 bit signed register so as per my understanding 0 - 7FFF is for positive power factor and 8000 - FFFF is for negative power factor but in my case register output is only in range 0 -7FFF and it never go in negative range even if power factor is negative
for above all calibration and testing process i have used standard source and standard meter with accuracy 0.025.