Datasheet
ADE7752/ADE7752A
Rev. C | Page 15 of 24
TYPICAL CONNECTION DIAGRAMS
CURRENT CHANNEL CONNECTION METER CONNECTIONS
Figure 19 shows a typical connection diagram for the current
channel (IA). A current transformer (CT) is the current trans-
ducer selected for this example. Notice the common-mode
voltage for the current channel is AGND and is derived by
center tapping the burden resistor to AGND. This provides the
complementary analog input signals for IAP and IAN. The CT
turns ratio and burden resistor Rb are selected to give a peak
differential voltage of ±500 mV at maximum load.
In 3-phase service, two main power distribution services exist:
3-phase 4-wire or 3-phase 3-wire. The additional wire in the
3-phase 4-wire arrangement is the neutral wire. The voltage
lines have a phase difference of ±120° (±2π/3 radians) between
each other. See Equation 5.
()
()
()
()
⎟
⎠
⎞
⎜
⎝
⎛
+××=
⎟
⎠
⎞
⎜
⎝
⎛
+××=
××=
3
π4
cos2
3
π2
cos2
cos2
tωVtV
tωVtV
tωVtV
l
CC
l
BB
l
AA
(5)
IAP
±500mV
R
b
Rf
Rf
CT
NEUTRALPHASE
IP
IAN
Cf
Cf
02676-A-019
where V
Figure 19. Typical Connection for Current Channels
VOLTAGE CHANNELS CONNECTION
Figure 20 shows two typical connections for the voltage
channel. The first option uses a potential transformer (PT) to
provide complete isolation from the main voltage. In the second
option, the ADE7752 is biased around the neutral wire, and a
resistor divider is used to provide a voltage signal proportional
to the line voltage. Adjusting the ratio of Ra, Rb, and VR is also
a convenient way of carrying out a gain calibration on the meter.
±500mV
Ra
*
Rb
*
VR
*
VAP
AGND
Rf
Rf
PT
NEUTRALPHASE
VN
Cf
Cf
VAP
Rf
NEUTRALPHASE
VN
Cf
Cf
*
Ra >> Rf + VR;
*
Rb + VR = Rf
02676-A-018
±500mV
Figure 20. Typical Connections for Voltage Channels
A
, V
B
, and V
C
B represent the voltage rms values of the
different phases.
The current inputs are represented by Equation 6.
()
(
)
()
()
⎭
⎬
⎫
⎩
⎨
⎧
++×=
⎭
⎬
⎫
⎩
⎨
⎧
++×=
+×=
C
l
CC
B
l
BB
A
l
AA
φtωItI
φtωItI
φtωItI
3
π4
cos2
3
π2
cos2
cos2
(6)
where I
A
, I
B
, and I
C
B represent the rms value of the current of
each phase and ϕ
A
, ϕ
B
B, and ϕ
C
represent the phase difference of
the current and voltage channel of each phase.
The instantaneous powers can then be calculated as follows:
P
A
(t) = V
A
(t) × I
A
(t)
P
B
(t) = V
B
B(t) × IB
B
(t)
P
B
C
(t) = V
C
(t) × I
C
(t)
Then:
(
)
()
(
)
()
()
()
()
⎟
⎠
⎞
⎜
⎝
⎛
++××−××=
⎟
⎠
⎞
⎜
⎝
⎛
++××−××=
+
××−
×
×
=
C
l
CCCCCC
B
l
BBBBBB
A
l
AAAAAA
φtωIVφIVtP
φtωIVφIVtP
φtωIVφIVtP
3
π8
2coscos
3
π4
2coscos
2coscos
(7)
As shown in Equation 7, in the ADE7752, the real power calcu-
lation per phase is made when current and voltage inputs of one
phase are connected to the same channel (A, B, or C). Then the
summation of each individual real power calculation gives the
total real power information, P(t) = P
A
(t) + P
B
(t) + P
C
(t).B