Rockwell Automation Publication 1412-UM001D-EN-P - September 2012 85
Appendix C
Mathematical Formulas For Various Parameters
Half-period Voltage and
Current RMS Values
• NSHC: number of samples per half cycle (between two consecutive zeros)
• n: sample (0; 255)
• i: phase (0; 1; 2)
MIN / MAX Values for Voltage
and Current
Vmax[i]=max (Vdem[i]), Vmin[i]=min (Vdem[i]), Vavg=1/6000 Vdem [i ]
Umax[i]=max (Udem[i]), Umin[i]=min (Udem[i]), Aavg=1/6000
Adem[i]
Amax[i]=max (Adem[i]), Amin[i]=min (Adem[i]) (Avg calculation on 1s)
Peak Values for Voltage and
Current
These values are updated on each waveform refresh.
Vpp[i]=max (V[i][n]), Vpm[i]=min (V[i][n]), n
[0..NSC-1]
Upp[i]=max (U[i][n]), Upm[i]=min (U[i][n]), n
[0..NSC-1]
App[i]=max (A[i][n]), Apm[i]=min (V[i][n]), n
[0..NSC-1]
NSC: number of samples per cycle
[] [][ ]
2
Vdem
:
2
∑
⋅=
Next Zero
Zeron
niV
NSHC
i
Single rms voltage half-period i + 1 phase
[] [][ ]
2
Udem
Compound rms voltage half-period i + 1 phase
:
2
∑
⋅=
Next Zero
Zeron
niU
NSHC
i
[] [][ ]
2
Adem
:
2
∑
⋅=
Next Zero
Zeron
niA
NSHC
i
Rms current half-period i + 1 phase
