ADE7880ACPZ-RL(RevA) View Datasheet(PDF) - Analog Devices
Part Name
Description
Manufacturer
ADE7880ACPZ-RL
(Rev.:RevA)
(Rev.:RevA)
Analog Devices
ADE7880ACPZ-RL Datasheet PDF : 104 Pages
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ADE7880
Data Sheet
ACTIVE (–)
REACTIVE (–)
PF (+)
ACTIVE (+)
REACTIVE (–)
PF (–)
CAPACITIVE:
CURRENT LEADS
VOLTAGE
θ = +60° PF = –0.5
V
θ = –60° PF = +0.5
enabled on both the active and apparent energies. This is done
by setting the xLWATT and xLVA bits in the LCYCMODE
register (Address 0xE702). The update rate of the power factor
measurement is now an integral number of half line cycles that
can be programmed into the LINECYC register (Address 0xE60C).
For full details on setting up the line cycle accumulation mode
see the Line Cycle Active Energy Accumulation Mode and Line
Cycle Apparent Energy Accumulation Mode sections.
ACTIVE (–)
REACTIVE (+)
PF (–)
I
ACTIVE (+)
REACTIVE (+)
PF (+)
INDUCTIVE:
CURRENT LAGS
VOLTAGE
Figure 81. Capacitive and Inductive Loads
Note that the power factor measurement is effected by the no
load condition if it is enabled (see the No Load Condition
section). If the apparent energy no load is true, then the power
factor measurement is set to 1. If the no load condition based
on total active and apparent energies is true, the power factor
measurement is set at 0.
As shown in Figure 81, the reactive power measurement is
negative when the load is capacitive, and positive when the load
is inductive. The sign of the reactive power can therefore be
used to reflect the sign of the power factor. Note that the ADE7880
computes the fundamental reactive power, so its sign is used as
the sign of the absolute power factor. If the fundamental
reactive power is in no load state, then the sign of the power
factor is the sign of the total active power.
The mathematical definition of power factor is shown in
Equation 47:
Power Factor = (Sign Fundamental Reactive Power) ×
Total Active Power
(47)
Apparent Power
As previously mentioned, the ADE7880 provides a power factor
measurement on all phases simultaneously. These readings are
provided into three 16-bit signed registers, APF (Address
0xE609 ) for Phase A, BPF (Address 0xE60A) for Phase B, and
CPF (Address 0xE60B) for Phase C. The registers are signed
twos complement register with the MSB indicating the polarity
of the power factor. Each LSB of the APF, BPF, and CPF
registers equates to a weight of 2−15, hence the maximum
register value of 0x7FFF equating to a power factor value of 1.
The minimum register value of 0x8000 corresponds to a power
factor of −1. If because of offset and gain calibrations, the power
factor is outside the −1 to +1 range, the result is set at −1 or +1
depending on the sign of the fundamental reactive power.
By default the instantaneous total phase active and apparent
powers are used to calculate the power factor and the registers
are updated at a rate of 8 kHz. The sign bit is taken from the
instantaneous fundamental phase reactive energy measurement
on each phase.
Should a measurement with more averaging be required, the
ADE7880 provides an option of using the line cycle accumulation
measurement on the active and apparent energies to determine
the power factor. This option provides a more stable power
factor reading. This mode is enabled by setting the PFMODE
bit (Bit 7) in the LCYCMODE register (Address 0xE702). When
this mode is enabled the line cycle accumulation mode must be
The ADE7880 also computes the power factor on the
fundamental and harmonic components based on the
fundamental and harmonic active, reactive and apparent
powers. See the Harmonics Calculations section for details.
HARMONICS CALCULATIONS
The ADE7880 contains a harmonic engine that analyzes one
phase at a time. Harmonic information is computed with a no
attenuation pass band of 2.8 kHz (corresponding to a −3 dB
bandwidth of 3.3 kHz) and it is specified for line frequencies
between 45 Hz and 66 Hz. Neutral current can also be analyzed
simultaneously with the sum of the phase currents. Figure 82
presents a synthesized diagram of the harmonic engine, its
settings and its output registers.
Theory of Operation
Consider an nonsinusoidal ac system supplied by a voltage, v(t)
that consumes the current i(t). Then
∞
v(t) = ∑Vk 2 sin (kωt + φk)
(48)
k=1
∞
i(t) = ∑ Ik
2 sin(kωt + γ k )
k =1
where:
Vk, Ik are rms voltage and current, respectively, of each
harmonic.
Φk, γk are the phase delays of each harmonic.
ω is the angular velocity at the fundamental (line) frequency f.
The ADE7880 harmonics calculations are specified for line
frequencies between 45 Hz and 66 Hz. The phase nominal
voltage used as time base must have an amplitude greater than
20% of full scale.
The number of harmonics N that can be analyzed within the
2.8 kHz pass band is the whole number of 2800/f. The absolute
maximum number of harmonics accepted by the ADE7880
is 63.
N
=
⎡
⎢
⎣
2800
f
⎤
⎥
⎦
,
N≤63
Rev. A | Page 56 of 104
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