2.2.1.1 Calculating Phase Calibration Factor Using Accumulator Values

The following formula is used to calibrate the phase delay of phase x making use of values from the integration period accumulators:

CAL_PH_Vx = 0x00000000

CAL_PH_Ix = CAL_PH_IxIV (if voltage channel phase calibration is not required)

Where:

  • ACC_Q_x_F – Reactive power fundamental-only integration accumulator value.
  • ACC_P_x_F – Active power fundamental-only integration accumulator value.
  • θVI – Test condition phase angle between voltage and current (+ inductive).
  • f_line – The power line frequency used for calibration.
Note: The above calibration equation can be used for manual calibration at any angle, while the auto calibration routines provided in the demonstration application program may be constrained to run at PF = 0.5Lag (60° lagging) condition only.
Note: For calibrating the neutral current phase delay, the fictitious accumulators ACC_Q_x_F and ACC_P_x_F have been added. These are computed using the neutral current and the dominant voltage.

Example:

An integration period of 1 second is used to gather the following accumulator values used for calibration, with conditions: 120V, 30A, PF = 0.5Lag (50 Hz), K_V = 11557, K_I = 308.642

ACC_P_x_F = 0x33C7784C5B = 222389881947

ACC_Q_x_F = 0x5A1E99C15E = 387060449630

Note: In the above discussion and example, phase calibration factors are computed for the current channels, regardless of whether voltage-voltage phase correction is computed. When phase calibration between voltage channels is not desired, all other calibration factors (magnitude and current channel phase correction factors) may be computed from accumulator registers from a single integration period. For best results when phase calibration between voltage channels IS desired, first calibrate and apply all magnitude gain factors before measuring and calibrating the voltage phase correction values, for additional information, refer to the Phase Calibration Between Voltage Channels.