ade7880 Analog Devices, Inc., ade7880 Datasheet - Page 30

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

ADE7880
Phase C, Phase B, or Phase A cannot come after zero crossings
from Phase A, Phase C, or respectively, Phase B zero crossings.
Once a phase sequence error has been detected, the time
measurement between various phase voltages (see the Time
Interval Between Phases section) can help to identify which
phase voltage should be considered with another phase current
in the computational datapath. Bits[9:8] (VTOIA[1:0]),
Bits[11:10] (VTOIB[1:0]), and Bits[13:12] (VTOIC[1:0]) in the
CONFIG register can be used to direct one phase voltage to the
datapath of another phase. See the Changing Phase Voltage
Datapath section for details.
Time Interval Between Phases
The ADE7880 has the capability to measure the time delay
between phase voltages, between phase currents, or between
voltages and currents of the same phase. The negative-to-positive
transitions identified by the zero-crossing detection circuit are
used as start and stop measuring points. Only one set of such
measurements is available at one time, based on Bits[10:9]
(ANGLESEL[1:0]) in the COMPMODE register.
When the ANGLESEL[1:0] bits are set to 00, the default value,
the delays between voltages and currents on the same phase are
measured. The delay between Phase A voltage and Phase A
current is stored in the 16-bit unsigned ANGLE0 register (see
Figure 29 for details). In a similar way, the delays between
STATUS1 REGISTER
BIT 19 (SEQERR) IN
VOLTAGES AFTER
A, B, C PHASE
Figure 27. SEQERR Bit Set to 1 When Phase A Voltage Is Followed by
Figure 28. Regular Succession of Phase A, Phase B, and Phase C
LPF1
IRQ1
ZX A
PHASE A
STATUS1[19] SET TO 1
ZX A
PHASE A
Phase C Voltage
ZX B
PHASE B
ZX C
PHASE C
STATUS1[19] CANCELLED
STATUS1 REGISTER WITH
BY A WRITE TO THE
ZX C
SEQERR BIT SET
PHASE C
ZX B
PHASE B
Rev. PrE | Page 30 of 103
voltages and currents on Phase B and Phase C are stored in the
ANGLE1 and ANGLE2 registers, respectively.
When the ANGLESEL[1:0] bits are set to 01, the delays between
phase voltages are measured. The delay between Phase A
voltage and Phase C voltage is stored into the ANGLE0 register.
The delay between Phase B voltage and Phase C voltage is
stored in the ANGLE1 register, and the delay between Phase A
voltage and Phase B voltage is stored in the ANGLE2 register
(see Figure 30 for details).
When the ANGLESEL[1:0] bits are set to 10, the delays between
phase currents are measured. Similar to delays between phase
voltages, the delay between Phase A and Phase C currents is
stored into the ANGLE0 register, the delay between Phase B
and Phase C currents is stored in the ANGLE1 register, and the
delay between Phase A and Phase B currents is stored into the
ANGLE2 register (see Figure 30 for details).
The ANGLE0, ANGLE1, and ANGLE2 registers are 16-bit
unsigned registers with 1 LSB corresponding to 3.90625 μs
(256 kHz clock), which means a resolution of 0.0703° (360° ×
50 Hz/256 kHz) for 50 Hz systems and 0.0843° (360° × 60 Hz/
256 kHz) for 60 Hz systems. The delays between phase voltages
or phase currents are used to characterize how balanced the
load is. The delays between phase voltages and currents are
used to compute the power factor on each phase as shown in
the following Equation 5:
where f
cosφ
Figure 29. Delay Between Phase A Voltage and Phase A Current Is
LINE
x
Figure 30. Delays Between Phase Voltages (Currents)
= cos
= 50 Hz or 60 Hz.
ANGLE2
PHASE A




VOLTAGE
PHASE A
ANGLEx
ANGLE0
Stored in the ANGLE0 Register
Preliminary Technical Data
ANGLE0
ANGLE1
×
PHASE B
360
CURRENT
PHASE A
256

×
kHz
f
LINE




PHASE C
(5)