ADE7763 View Datasheet(PDF) - Analog Devices
Part Name
Description
MFG CO.
'ADE7763' PDF : 56 Pages View PDF
The active power signal (output of LPF2) can be rewritten as
⎡
⎤
⎢
⎥
⎢
p(t) = VI − ⎢
⎢
⎢
VI
⎥
⎥ × cos(4π
1+
⎜⎛
2
fL
⎟⎞ 2
⎥
⎥
fL t)
(18)
⎢⎣ ⎝ 8.9 ⎠ ⎥⎦
where fL is the line frequency, for example, 60 Hz.
From Equation 13,
⎡
⎤
⎢
⎥
⎢
E(t) = VIt − ⎢
VI
⎥
⎥ × sin(4π f L t)
(19)
⎢
⎢ 4π
⎢⎣
fL
1+
⎜⎛
2
fL
⎟⎞ 2
⎥
⎥
⎝ 8.9 ⎠ ⎥⎦
Note that in Equation 19 there is a small ripple in the energy
calculation due to a sin(2ωt) component. This is shown graphi-
cally in Figure 60. The active energy calculation is represented
by the dashed, straight line and is equal to V × I × t. The sinu-
soidal ripple in the active energy calculation is also shown.
Because the average value of a sinusoid is 0, the ripple does not
ADE7763
contribute to the energy calculation over time. However, the
ripple might be observed in the frequency output, especially at
higher output frequencies. The ripple becomes larger as a
percentage of the frequency at larger loads and higher output
frequencies. This occurs because the integration or averaging
time in the energy-to-frequency conversion process is shorter at
higher output frequencies. Consequently, some of the sinusoidal
ripple in the energy signal is observable in the frequency output.
Choosing a lower output frequency at CF for calibration can
significantly reduce the ripple. Also, averaging the output
frequency by using a longer gate time for the counter achieves
the same results.
E(t)
Vlt
–
VI
4×π×fL(1+2×fL/8. 9Hz )
sin(4×π×fL×t)
t
Figure 60. Output Frequency Ripple
OUTPUT
FROM
LPF2
WGAIN[11:0]
++
48
%
APOS[15:0]
WDIV[7:0]
FROM
CHANNEL 2
ADC
LPF1
ZERO CROSSING
DETECTION
CALIBRATION
CONTROL
23
0
LAENERGY[23:0]
0
ACCUMULATE ACTIVE
ENERGY IN INTERNAL
REGISTER AND UPDATE
THE LAENERGY REGISTER
AT THE END OF LINECYC
LINE CYCLES
LINECYC[15:0]
Figure 61. Energy Calculation Line Cycle Energy Accumulation Mode
Rev. A | Page 29 of 56
Share Link: 
