For the following test results, gain, phase, and offset calibration are applied to the meter. At higher currents, the % error shown is dominated by shunt resistance drift caused by the increased heat generated at high currents.

For cumulative active energy error, cumulative reactive energy error testing, and individual phase active energy testing, current is varied from 100mA to 100A. For cumulative active energy and individual phase error testing, a phase shift of 0° (PF = 1), PF = 0.5i (inductive) and PF = 0.8c (capacitive) is applied between the voltage and current waveforms fed to the reference design. Based on the error from the active energy output pulse, a plot of active energy % error versus current is created for the three PF values.

For cumulative reactive energy error testing, a similar process is followed except that a phase shift of 90° (sin ϕ = 1i), sin ϕ = 0.5i (inductive) and sin ϕ = 0.8c (capacitive) are used, and cumulative reactive energy error is plotted instead of cumulative active energy error.

In both cumulative active and reactive energy testing, the sum of the energy reading of each phase is tested for accuracy. In contrast, the individual phase energy readings (Phase A and Phase B, if split-phase mode is used) are tested for the individual phase active energy testing. When testing the individual energy accuracy of a phase, the other phase is disabled by providing 0A input for the current of this other phase so that the cumulative active energy reading is ideally equal to the individual phase voltage, which allows the cumulative energy pulse output to be used for testing individual phase accuracy. All these tests were run using the 4kSPS sample rate setting of the ADS131M02 and AMC131M03 devices.

For the V_RMS accuracy test on both Phase A and B, the voltage was varied from 10V to 270V while current was held steady at 10A. Testing beyond 270V can also be done; however, this requires the 275V varistors to be removed from the design and replaced with varistors that are rated for a higher voltage.

For the I_RMS accuracy test on both Phase A and B, the voltage was kept steady at 120V, while current was varied from 0.1A to 100A.

The following 4 plots for Active and Reactive Power for Star and Delta Configurations are per IEC 62053-22 limits for class 0.2 S accuracy, assuming I_nominal = 15A, hence the 5% point of I_nominal is at 750mA.

The average error for each measurement is calculated from five test series, taken sequentially for each current value, and the maximum deviation from these five measurements is calculated (not shown in the plots below) to confirm the stability of this metrology subsystem being below 10% of the maximum error allowed.

Figure 3-17 ACTive Energy % Error Versus Current, 200μΩ Shunts, Star (Wye) Configuration

Figure 3-18 REACTive Energy % Error Versus Current, 200μΩ Shunts, Star (Wye) Configuration

Figure 3-19 ACTive Energy % Error Versus Current, 200μΩ Shunts, Delta Configuration

Figure 3-20 REACTive Energy % Error Versus Current, 200μΩ Shunts, Delta Configuration

Figure 3-21 through Figure 3-24 show the I_RMS and V_RMS per each phase, where the % error column is generated by comparing the respective MTE Reading and the GUI reading. For these plots single measurements were recorded.

Figure 3-21 V_RMS % Error at 10A, 200μΩ Shunts, Phase A

Figure 3-22 I_RMS % Error at 120V, 200μΩ Shunts, Phase A

Figure 3-23 V_RMS % Error at 10A, 200μΩ Shunts, Phase B

Figure 3-24 I_RMS % Error at 120V, 200μΩ Shunts, Phase B