ADE7761ARS-REF Analog Devices Inc, ADE7761ARS-REF Datasheet - Page 21

• Manufacturer Part Number: ADE7761ARS-REF
• Description: IC ENERGY METERING 20-SSOP
• Manufacturer: Analog Devices Inc

Specifications of ADE7761ARS-REF

• Rohs Status: RoHS non-compliant

The ADE7761 detects a missing neutral condition by continu-
ously monitoring the voltage channel input (V
FAULT pin is held high when a missing neutral condition is
detected. In this mode, the ADE7761 continues to bill the
energy based on the signal level on the current channel (see
Figure 30). The billing rate or frequency outputs can be adjusted
by changing the dc level on the MISCAL pin.
GENERATOR
V
V
V
MISCAL
1A
1N
1B
240V RMS
POWER
LOAD
Figure 30. Energy Calculation in Missing Neutral Mode
Figure 29. Missing Neutral System Diagram
ADC
ADC
ADC
IB
A > B
B > A
B <> A
MISSING NEUTRAL
GAIN ADJUSMENT
HPF
*RB + VR = RF
RA*
RB*
VR*
CT
CT
DETECTION
CROSSING
ZERO
RB
RB
R
C
F
C
F
T
V1A
0V
R
R
F
F
V
V
2P
2P
2N
–V
C
C
V
V
V
F
F
1A
1N
1B
CONVERTERS
CF F1 F2
2N
FREQUENCY
DIGITAL-
). The
TO-
LPF
Rev. A | Page 21 of 28
Important Note for Billing of Active Energy
The ADE7761 provides pulse outputs—CF, F1, and F2—
intended to be used for the billing of active energy. Pulses are
generated at these outputs in two different situations.
Case 1: When the analog input V
conditions described in Figure 32, CF, F1, and F2 frequencies
are proportional to active power and can be used to bill active
energy.
Case 2: When the analog input V
the conditions described in Figure 32, the ADE7761 does not
measure active energy, but a quantity proportional to kAh. This
quantity is used to generate pulses on the same CF, F1, and F2.
This situation is indicated when the FAULT pin is high.
Analog Devices Inc. cautions users of the ADE7761:
•
•
Missing Neutral Detection
The ADE7761 continuously monitors the voltage input and
detects a missing neutral condition when the voltage input peak
value is smaller than 9% of the analog full scale or when no zero
crossings are detected on this input (see Figure 31).
|V2|
AGND
9% OF FS
PEAK
Billing active energy in Case 1 is consistent with the
understanding of the quantity represented by pulses on
CF, F1, and F2 outputs (watt-hour).
Billing active energy while the ADE7761 is in Case 2 must
be decided knowing that the entity measured by the
ADE7761 in this case is ampere-hour and not watt-hour.
Users should be aware of this limitation and decide if the
ADE7761 is appropriate for their application.
V2
V
0V
FS
2P
< 9% OF FULL SCALE
–V
V
V
2P
2N
2N
Figure 31. Missing Neutral Detection
V
0V
FS
2P
OR
–V
ADC
2N
NO ZERO-CROSSING ON V2
2P
2P
– V
– V
THRESHOLD
FILTER AND
2N
2N
complies with the
does not comply with
V
FS
0V
2P
–V
2N
MISSING
NEUTRAL
ADE7761