ade7880 Analog Devices, Inc., ade7880 Datasheet - Page 65

• Manufacturer Part Number: ade7880
• Description: Polyphase Multifunction Energy Metering Ic With Harmonic Monitoring
• Manufacturer: Analog Devices, Inc.

Preliminary Technical Data
When VARACC[1:0] = 11, the fundamental reactive powers are
accumulated in absolute mode. When the powers are negative,
they change sign and accumulate together with the positive
power in the var-hour registers and before entering the energy-to-
frequency converter. In this mode, the CFx pulses synchronize
perfectly with the fundamental reactive energy accumulated in
xVARHR registers because the powers are accumulated in the same
way in both data paths. Figure 70 shows how absolute
fundamental reactive power accumulation works.
Sign of Sum-of-Phase Powers in the CFx Datapath
The ADE7880 has sign detection circuitry for the sum of phase
powers that are used in the CFx datapath. As seen in the
beginning of the Energy-to-Frequency Conversion section, the
energy accumulation in the CFx datapath is executed in two
stages. Every time a sign change is detected in the energy
Figure 68. Fundamental Reactive Power Signed Accumulation Mode
ACTIVE ENERGY
ACTIVE POWER
xVARSIGN BIT
THRESHOLD
THRESHOLD
REVRPx BIT
THRESHOLD
THRESHOLD
IN STATUS0
REVAPx BIT
xWSIGN BIT
IN STATUS0
IN PHSIGN
REACTIVE
REACTIVE
NO-LOAD
NO-LOAD
IN PHSIGN
ENERGY
NO-LOAD
NO-LOAD
Figure 67. Active Power Absolute Accumulation Mode
POWER
SIGN = POSITIVE
SIGN = POSITIVE
VARNOLOAD
APNOLOAD
POS
POS
NEG
NEG
POS
POS
NEG
NEG
Rev. PrE | Page 65 of 103
accumulation at the end of the first stage, that is, after the
energy accumulated into the accumulator reaches one of the
WTHR, VARTHR, or VATHR thresholds, a dedicated interrupt
can be triggered synchronously with the corresponding CFx
pulse. The sign of each sum can be read in the PHSIGN register.
Bit 18, Bit 13, and Bit 9 (REVPSUM3, REVPSUM2, and
REVPSUM1, respectively) of the STATUS0 register are set
to 1 when a sign change of the sum of powers in CF3, CF2,
or CF1 datapaths occurs. To correlate these events with the
pulses generated at the CFx pins, after a sign change occurs,
Bit REVPSUM3, Bit REVPSUM2, and Bit REVPSUM1 are set
xVARSIGN bit
Figure 70. Fundamental Reactive Power Accumulation in Absolute Mode
Figure 69. Fundamental Reactive Power Accumulation in Sign Adjusted
THRESHOLD
THRESHOLD
in PHSIGN
in STATUS0
REVRPx bit
REACTIVE
REACTIVE
NO-LOAD
NO-LOAD
ENERGY
POWER
xVARSIGN BIT
THRESHOLD
THRESHOLD
THRESHOLD
REVRPx BIT
IN STATUS0
REACTIVE
REACTIVE
IN PHSIGN
NO-LOAD
NO-LOAD
NO-LOAD
ENERGY
POWER
POWER
ACTIVE
SIGN=POSITIVE
VARNOLOAD
SIGN = POSITIVE
VARNOLOAD
Mode
POS
POS
NEG
NEG
POS
ADE7880
POS
NEG