EVAL-ADE7752EB Analog Devices Inc, EVAL-ADE7752EB Datasheet - Page 2

• Manufacturer Part Number: EVAL-ADE7752EB
• Manufacturer: Analog Devices Inc

Specifications of EVAL-ADE7752EB

• Lead Free Status / Rohs Status: Not Compliant

EVAL-ADE7752EB
ANALOG INPUTS (P4, P5, P6, P7, P8 AND P11)
ANALOG INPUTS (P4, P5, P6, P7, P8 AND P11)
ANALOG INPUTS (P4, P5, P6, P7, P8 AND P11)
Voltage and current signals are connected at the screw
terminals P4-P6 and P7-P8 and P11 respectively. All analog
input signals are filtered using the on-board anti-alias filters
before being presented to the analog inputs of the ADE7752.
The default component values which are shipped with the
evaluation board are the recommended values to be used with
the ADE7752. The user can easily change these components,
however this is not recommended unless the user is familiar
with sigma-delta converters and also the criteria used for
selecting the component values for the analog input filters -
See ADE7752 datasheet.
Current sense inputs (P4, P5 and P6)
P4, P5 and P6 are two-way connection blocks which allow
ADE7752's current inputs of phase A, B and C respectively
to be connected to current transducers. Figure 1 shows the
connector P4 and the filtering network which is provided on
the evaluation board.
The resistors SH1A, SH2A, SH1B, SH2B, SH1C and
SH2C are by default not populated. They are intended to be
used as burden resistors when CTs are used as the current
transducers—see using a CT as a the current transducer.
The RC networks R9/C5, R7/C8, R15/C9, R13/C12, R21/
C13, R19/C16 are used to provide phase compensation when
a Current Transformer is being used as the current transducer
with the ADE7752—see using a Current Transformer as the
current transducer. These RC networks are easily disabled by
placing JP4, JP1, JP10, JP7, JP16 & JP13 and removing C5,
C8, C9, C12, C13 and C16 (socketed).
The RC networks R10/C6, R8/C7, R16/C10, R14/C11,
R22/C14 and R20/C15 are the anti-alias filters which are
required by the on-chip ADCs. The default corner frequency
for these LPFs (Low Pass Filters) is selected as 4.8kHz (1kΩ
& 33nF). These filters can easily be adjusted by replacing the
components on the evaluation board. However before adjust-
ing the component values the user should first review the
ADE7752 datasheet.
ANALOG INPUTS (P4, P5, P6, P7, P8 AND P11)
ANALOG INPUTS (P4, P5, P6, P7, P8 AND P11)
P4 1
P4 2
Figure 1 — Current Channel on the ADE7752 evaluation
SH1A
R11
SH2A
R6
JP2
JP3
JP4
JP1
100Ω
100Ω
R7
R9
board
C5
33nF
C8
33nF
JP6
JP5
R8
1kΩ
R10
1kΩ
PRELIMINARY TECHNICAL DATA
PRELIMINARY TECHNICAL DATA
C6
33nF
C7
33nF
TP2
TP4
ADE7752
IAN
IAP
– 2 –
Using a CT as the current transducer
Figure 2 shows how a CT can be used as a current transducer
in one phase of a 3-phase 4-wire distribution system (Phase
A). In a three phase distribution system Phase A, Phase B and
Phase C are nominally 120° phase difference to each other.
Each phase usually requires a connection of this type for
current sensing.
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, i.e., no burden is
connected, a large voltage could be present at the secondary
outputs. This can cause an electrical shock hazard and
potentially damage electronic components.
The anti-alias filters should be enabled by opening jumpers
JP5, JP6, JP11, JP12, JP17 and JP18—see Figure 2.
Most CTs will have an associated phase shift of between 0.1°
and 1° at 50Hz/60Hz. This phase shift or phase error can lead
to significant energy measurement errors, especially at low
power factors. However this phase error can be corrected by
adding some capacitors in parallel to C6 and C7.
The maximum analog input range on the Current channel of
the ADE7752 is 0.5V peak.
I max = 40A
1:1800
CT
Figure 2 — CT connection to Current Channel
Warning!
Using a CT without a burden resistor
can lead to electrical shock.
SH1A
SH2A
8Ω
8Ω
JP2
JP4
JP1
JP25
100Ω
100Ω
Full Scale
differential input = 0.5V
JP5
JP6
1kΩ
1kΩ
REV. PrB 06/02
33nF
33nF
TP2
TP4
ADE7752
IAP
IAN
355mV
rms