ade7763 Analog Devices, Inc., ade7763 Datasheet - Page 29

• Manufacturer Part Number: ade7763
• Description: Single-phase Active And Apparent Energy Metering Ic
• Manufacturer: Analog Devices, Inc.

The active power signal (output of LPF2) can be rewritten as
where f
From Equation 13,
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
E
p
(
(
L
t
t
is the line frequency, for example, 60 Hz.
)
)
VI
VIt
CHANNEL 2
4
1
OUTPUT
FROM
FROM
f
LPF2
ADC
VI
L
2
8
9 .
f
1
L
VI
APOS[15:0]
2
LPF1
2
8
9 .
f
L
cos(
WGAIN[11:0]
2
4
ZERO CROSSING
Figure 61. Energy Calculation Line Cycle Energy Accumulation Mode
DETECTION
sin(
f
L
4
t
)
f
L
t
WDIV[7:0]
)
%
LINECYC[15:0]
CALIBRATION
CONTROL
Rev. A | Page 29 of 56
+
(18)
(19)
+
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.
48
23
LAENERGY[23:0]
E(t)
–
Figure 60. Output Frequency Ripple
0
4
ACCUMULATE ACTIVE
ENERGY IN INTERNAL
REGISTER AND UPDATE
THE LAENERGY REGISTER
AT THE END OF LINECYC
LINE CYCLES
f
L
t
Vlt
(1+2 f
VI
L
/8. 9Hz )
0
sin(4
f
L
t)
ADE7763