UG-572 Datasheet, PDF (18/20 Pages) Winchester Electronics Corporation – C JACK

UG-572
Figure 32. Power Quality Sag Detection
EVAL-ADE7978EBZ User Guide
then averages them (this reduces jitter in the measurement,
therefore increasing the accuracy).
The program then computes the full-scale voltages and currents
and the constants that are important for setting up the ADE7978:
the constant n, CFDEN, WTHR, VARTHR, VATHR, VLEVEL,
and VNOM. The expressions used to determine these constants
are the ones presented in the ADE7978/ADE7933/ADE7932
data sheet.
The values calculated by the quick start program can be
overwritten. Update Registers allows you to:
• Initialize the gain, CF1DEN, CF2DEN, CF3DEN, WTHR,
VARTHR, VATHR, VLEVEL, and VNOM registers
• Enable the CF1 pin to provide a signal proportional to the
total active power, enable the CF2 pin to provide a signal
proportional to the fundamental reactive power, and
enable the CF3 pin to provide a signal proportional to the
apparent power.
• Select the state of Bit 14 (SELFREQ) in the COMPMODE
register based on the nominal line frequency, fn.
At this point, the evaluation board is set up as a three-phase
meter, and calibration can be performed. To store the register
initializations, click Save to File in the All Register Access
window (see Figure 15). If the board is reset for any reason, the
registers can be loaded into the ADE7978 by loading the
contents of the data file. To do this, click Load from File in the
All Register Access window.
Figure 33. Power Quality Time Interval Between Phases
QUICK SETUP
The Quick Setup window is shown in Figure 34. This window
can be used to rapidly initialize a three-phase meter. Set the
Meter Constant (MC, in impulses/kWh), the Nominal Voltage
(VN, in V rms units), the Nominal Current (IN, in A rms
units), and the Nominal Line Frequency (fn, either 50 Hz or 60
Hz) must be set using the window controls.
Begin Computations starts the program that reads rms
voltages and currents and calculates the full-scale voltage and
currents used to further initialize the meter. This process reads
the rms voltages 100 times and the rms currents 100 times and
Figure 34. Quick Setup Window
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