2.2 Phase Delay

CAL_PH_Ix(x = A, B, C, N) and CAL_PH_Vx(x = A, B, C) are used to align the phase delays between each pair of current and voltage channels, and also to optionally equalize the phase delays between voltage channels. All phase shift coefficients used by the metrology DSP must be normalized to equivalent linear-phase shift amounts at 60 Hz.

There are two steps for phase calibration:

  1. Phase calibration between current channel and its voltage channel
  2. Phase calibration between voltage channels (optional)

If interphase vector manipulation or optimal phase-phase voltage measurement are not required, then step 2 is optional. If there is no need to make phase calibration between voltage channels, set all CAL_PH_Vx registers to the value: 0x00000000.

However, if interphase vector manipulation is desired or it is desired to achieve the highest accuracy in phase-phase voltage measurements, then it is required to adjust the voltage phase correction coefficients also.

Usually, acceptable calibration performance for energy-types of values may be obtained with a single calibration pass using the data from one integration period (usually 1 second or longer) using voltage and current values read directly from a standard or measurement device, with all phase correction coefficients computed simultaneously with the magnitude correction factors from that same set of integration data.

To obtain the most accurate performance for voltage and/or current measurements, one may, first, individually calibrate either the voltage or the current channels, usually using a pulse reference standard. For example, if all current channels are pulse magnitude calibrated for A2hr, then all the remaining calibration coefficients (voltage magnitude, current phase and voltage phase correction factors) may be determined with a single additional calibration pass using one set of integration data.