ADE7854AACPZ View Datasheet(PDF) - Analog Devices
Part Name
Description
MFG CO.
'ADE7854AACPZ' PDF : 96 Pages View PDF
ADE7854A/ADE7858A/ADE7868A/ADE7878A
Data Sheet
IA
APHCAL
VA
HPFDIS
[23:0]
HPF
HPFDIS
[23:0]
HPF
DIGITAL
INTEGRATOR AIGAIN
AWGAIN AWATTOS
AVGAIN
LPF2
DIGITAL SIGNAL PROCESSOR
Figure 66. Total Active Power Datapath
INSTANTANEOUS
PHASE A ACTIVE
POWER
AWATT
24
If the phase currents and voltages contain only the fundamental
0
component, are in phase (that is, φ1 = γ1 = 0), and they correspond
to full-scale ADC inputs, multiplying them results in an
–5
instantaneous power signal that has a dc component, V1 × I1,
and a sinusoidal component, V1 × I1 cos(2ωt); Figure 67 shows
the corresponding waveforms.
–10
INSTANTANEOUS
POWER SIGNAL
p(t)= V rms × I rms – V rms × I rms × cos(2ωt)
0x3FED4D6
–15
67,032,278
INSTANTANEOUS
ACTIVE POWER
SIGNAL: V rms × I rms
–20
V rms × I rms
0x1FF6A6B =
33,516,139
0x000 0000
i(t) = √2 × I rms × sin(ωt)
v(t) = √2 × V rms × sin(ωt)
–25
0.1
1
3
10
FREQUENCY (Hz)
Figure 68. Frequency Response of the LPF2 Used to Filter Instantaneous
Power in Each Phase: LPFSEL Bit of CONFIG_A Register Set to 0
0
–5
Figure 67. Active Power Calculation
Because LPF2 does not have an ideal brick wall frequency
response (see Figure 68), the active power signal has some
ripple caused by the instantaneous power signal. This ripple is
sinusoidal and has a frequency equal to twice the line frequency.
Because the ripple is sinusoidal in nature, it is removed when
the active power signal is integrated over time to calculate the
energy.
Bit 1 (LPFSEL) of the CONFIG_A register selects LPF2 strength.
Setting LPFSEL to 0 (default), the settling time is 650 ms and
the ripple attenuation is 65 dB. Setting LPFSEL to 1, the settling
time is 1300 ms and the ripple attenuation is 128 dB. Figure 68
shows the frequency response of the LPF2 when the LPFSEL bit
is set to 0, and Figure 69 shows the frequency response on the
LPF2 when the LPFSEL bit is set to 1.
–10
–15
–20
–25
0.1
1
3
10
FREQUENCY (Hz)
Figure 69. Frequency Response of the LPF2 Used to Filter Instantaneous
Power in Each Phase: LPFSEL Bit of CONFIG_A Register Set to 1
The ADE7854A/ADE7858A/ADE7868A/ADE7878A store the
instantaneous total phase active powers in the AWATT, BWATT,
and CWATT registers. The expression for the registers is
xWATT
Vk
k1 VFS
Ik
I FS
cos(φk − γk) × PMAX ×
1
24
(26)
where:
VFS, IFS are the rms values of the phase voltage and current when
the ADC inputs are at full scale.
Rev. C | Page 48 of 96
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