Appendix A: Mathematical Formulas; Half-Period Voltage And Current Rms Values; Min / Max Values For Voltage And Current - AEMC 8220 User Manual

Mathematical Formulas for Various Parameters
NOTE the following abbreviations used in this section:
NSHC = number of samples per half cycle (between two consecutive
zeros)
NSC = number of samples per cycle
NSS = number of samples in a second (multiple of NSC)
V = voltage phase to neutral
U = voltage phase to phase
Network Frequency
The sampling is locked to the network frequency so as to provide 256 samples per
period (NECHPER) from 40 to 70Hz. This locking is essential for the calculations
of the reactive powers, the calculations of levels and angles, and the calculations
giving the harmonic magnitudes.

Half-period Voltage and Current RMS Values

1
Vhalf
=
NSHC
1
Ahalf
=
NSHC
n: sample (0; 255)

MIN / MAX Values for Voltage and Current

Vmax=max (Vhalf), Vmin=min (Vhalf)
Amax=max (Ahalf), Amin=min (Ahalf)
62
APPENDIX A
(Next Zero)-1
[ ]
∑
2
V n
⋅
n : Zero
(Next Zero)-1
[ ]
∑
2
⋅ A n
n Zero
:
Rms voltage
Rms current
Power Quality Analyzer Model 8220