Analog Devices UG-061, Руководство пользователя

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UG-061 Evaluation Board User Guide
Rev. 0 | Page 8 of
USING A CT AS THE CURRENT TRANSDUCER
Figure 5 shows how a current transformer (CT) can be used as a
current transducer in a single-phase, 2-wire distribution system.
The CT secondary current is converted to a voltage by using a
burden resistance across the secondary winding outputs. Care
should be taken when using a CT as the current transducer. If
the secondary is left open, that is, no burden is connected, a
large voltage may be present at the secondary outputs. This can
cause an electrical shock hazard and potentially damage
electronic components.
When using a CT as the current sensor, the antialias filters
should be enabled by opening Jumper JP19 and Jumper JP1
(see Figure 8).
Most CTs have an associated phase shift of between 0.1° and 1°
at 50 Hz/60 Hz. This phase shift or phase error can lead to signifi-
cant energy measurement errors, especially at low power factors.
However, this phase error can be corrected by writing to the
phase calibration register (PHCAL[7:0]) in the ADE7169/
ADE5169. The software supplied with the ADE7169/ADE5169
evaluation board allows user adjustment of the phase calibra-
tion register. See the Evaluation Board Software section for
more information.
The maximum analog input range and gain for the current and
voltage channels are set via the gain register (see the respective
data sheet). The evaluation software allows the user to configure
the channel range and gain. This means that the maximum
peak differential signal on Channel 1 is 0.5 V (at gain = 1).
For an antitamper configuration, measuring both the phase and
neutral currents, two CTs can be used as shown in Figure 6. Other
antitamper current sensor options include one shunt and one
CT, as shown in Figure 7.
JP13
R11
1k
Ω
R43
0
Ω
R42
0
Ω
R17
51
Ω
JP16
JP14
R3
1k
Ω
JP1
C26
0.033µF
C23
0.033µF
R41
0
Ω
R16
51
Ω
JP11
R4
1k
Ω
JP19
C24
0.033µF
IP
IPA
IN
IPB/FP26
IN
IPB
IPA
IN
IPB
P11 1
P11 2
P11 3
08600-
059
PHASE
NEUTRAL
240V
LOA
D
ADE7169/
ADE5169
Figure 5. CT Sensor Connection to Current Channel
ADE7169/
ADE5169
JP13
R11
1k
Ω
R43
0
Ω
R42
0
Ω
R17
51
Ω
JP16
JP14
R3
1k
Ω
JP1
C26
0.033µF
C23
0.033µF
R41
0
Ω
R16
51
Ω
JP11
R4
1k
Ω
JP19
C24
0.033µF
IP
IPA
IN
IPB/FP26
IN
IPB
IPA
IN
IPB
P11 1
P11 2
P11 3
08600-
062
PHASE
NEUTRAL
240V
LOA
D
Figure 6. Connecting Two CTs to the Current Channels