ADE7878
ADE7878
P2 P1 P10 P12
P3
ICP
ICN Digital
LPC2368 USB Port
Isolators
Filter Network ADE78xx
INP
INN P13
P4 P15
Optional External
1.2V Reference ADR280 Optional External
Clock In
Connector to
PC COM Port
P5 P6 P7 P8 P9 J2 J3 J4
VN GND VCP GND VBP GND VAP GND VDD GND CF3 CF2 CF1
Rev. PrB
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EVAL-ADE7878EB Preliminary Technical Data
TABLE OF CONTENTS
Features .............................................................................................. 1 Front Panel Screen ....................................................................7
General Description ......................................................................... 1 PSM0 – Normal Power Mode..................................................8
Evaluation Board Power Supplies............................................... 3 Enter PSM1 Mode .................................................................. 15
Analog Inputs (P1, P2, P3, P4, P6, P7, and P8) ........................ 3 Enter PSM2 Mode .................................................................. 15
Current Sense Inputs (P1, P2, P3, and P4 Connectors) ...... 3 Enter PSM3 Mode .................................................................. 16
Using a Current Transformer as the Current Sensor .......... 3 Communication Protocol Between Microcontroller and
Votage Sense Inputs (P5, P6, P7, and P8 Connectors) ........ 4 ADE7878 ..................................................................................... 16
Setting Up the Evaluation Board as an Energy Meter ............. 5 Upgrading Microcontroller Firmware..................................... 19
Using the Evaluation Board with another microcontroller 7 Evaluation Board Schematic ..................................................... 23
the microcontroller and one side of the isocouplers, one that 100 1K
18000pF
18000pF
JP1A
C17
R1
supplies the other side of the optocouplers and one that supplies
C9
P1
ADE7878. The ground of the microcontroller’s power domain is IAP
connected to the ground of the PC through the USB cable. The IAN
18000pF
18000pF
ground of ADE7878 power domain is determined by the
JP2A
C10
C18
R2
ground of the phase voltages VAP, VBP, VCP and VN and must R10 R18
IAN
be different from the ground of the microcontroller’s power 100 1K
domain. TP2
JP4A JP6A
The microcontroller 3.3V supply is provided at P12 connector. Figure 2. Phase A Current Input Structure on Evaluation Board
ADE7878 3.3V supply is provided at P9 connector. The same
JP3A JP5A
supply should also be provided at P10 connector, the connector TP1
R17 ADE78xx
R9
that supplies the other side of the isocouplers. IAP
100 1K
18000pF
ANALOG INPUTS (P1, P2, P3, P4, P6, P7, AND P8) Imax=6 Arms
18000pF
JP1A
C17
R1
C9
50
CT
P1
1:2000
Current and voltage signals are connected at the screw
terminals P1 – P4 and P5 - P8 respectively. All analog input
18000pF
18000pF
signals are filtered using the on-board anti-aliasing filters before
JP2A
C10
C18
R2
50
being connected to ADE7878. The components used on the R10 R18 IAN
board are the recommended values to be used with ADE7878. 100 1K
TP2
Current Sense Inputs (P1, P2, P3, and P4 Connectors) JP4A JP6A
ADE7878 measures 3 phase currents and the neutral current. Figure 3. Example of a Current Transformer Connection
Current transformers or Rogowski coils can be used to sense The burden resistors R1 and R2 have to be chosen function of
the currents, but not mixed together. ADE7878 contains current transformer ratio and maximum current of the system.
different internal PGA gains on phase currents and on the The jumpers JP1A and JP2A should be opened if R1 and R2 are
neutral current, so sensors with different ratios can be used. used. The antialiasing filters should be enabled by opening
The only requirement is to have same scale signals at PGAs jumpers J5A and J6A (please see Figure 3).
outputs, otherwise the mismatch functionality of ADE7878 is
compromised (Please see Neutral Current Mismatch chapter in The transformer’s secondary current is converted to a voltage by
ADE7878 data sheet for more details). Figure 2 shows the using a burden resistor across the secondary winding outputs.
structure used for the phase A current: the sensor outputs are Care should be taken when using a current transformer as the
connected to P1 connector. The resistors R1 and R2 are the current sensor. If the secondary is left open, that is no burden is
burden resistors and by default, they are not populated. They connected, a large voltage could be present at the secondary
can also be disabled using JP1A and JP2A jumpers. The RC outputs. This can cause an electric shock hazard and potentially
networks R9/C9 and R10/C10 are used to provide phase damage electronic components.
compensation when a current transformer is being used. They Most current transformers introduce a phase shift that the
can be disabled using JP3A and JP4A jumpers. The RC manufacturer indicates in the data sheet. This phase shift can
networks R17/C17 and R18/C18 are the antialiasing filters. The lead to significant energy measurement errors, especially at low
default corner frequency of these low pass filters is 8.8KHz power factors. ADE7878 can correct the phase error using
(1KΩ/18nF). These filters can easily be adjusted by replacing APHCAL[9:0], BPHCAL[9:0] and CPHCAL[9:0] phase
the components on the evaluation board. calibration registers as long as the error stays between -6.732°
All the other current channels, that is phase B, phase C and and +1.107° at 50Hz. Please see ADE7878 data sheet for more
neutral current have similar input structure. details. The software supplied with the ADE7878 evaluation
board allows user adjustment of phase calibration registers.
Using a Current Transformer as the Current Sensor
For this particular example, burden resistors of 50 ohm signify
Figure 3 shows how a current transformer can be used as a an input current of 7.05 Arms at ADE7878 ADC full scale input
current sensor in one phase of a 3-phase 4-wire distribution (0.5V). In addition, the PGA gains for the current channel have
system (Phase A). The other two phases and the neutral current to be set at 1. For more information on setting PGA gains,
requires similar connections. please see ADE7878 data sheet. The evaluation software allows
the user to configure the current channel gain.
18000pF
1M 100K
C32
JP8B
R32
1K
network on the voltage channels is designed such that the
Phase A
corner frequency (3dB frequency) of the network matches that
Neutral
VN
1
A 2
COM 3
of the antialiasing filters in the current channels inputs. This JP9A
B
JP7N
prevents obtaining large energy errors at low power factors. P5
TP9
VN R25 VN
Figure 4 shows a typical connection of the phase A voltage
18000pF
1K
JP8N
C25
inputs: the resistor divider is enabled by opening JP7A jumper.
The antialiasing filter on VN data path is enabled by opening
JP7N jumper. JP8B and JP8N are opened. The analog input VN
Figure 4. Phase A Voltage Input Structure On Evaluation Board
is connected to AGND via the antialiasing filter R25/C25 using
JP8N connector. The maximum signal level permissible at VAP, VBP and VCP
pins of ADE7878 is 0.5V peak. Although ADE7878 analog
The attenuation networks can be easily modified by the user to
inputs can withstand ±2V without risk of permanent damage,
accommodate any input level. However, the value of R32 (1KΩ),
the signal range should not exceed ±0.5V with respect to
should be modified only together with the corresponding
AGND for specified operation.
SETTING UP THE EVALUATION BOARD AS AN and the control circuit, the power supplies should have floating
ENERGY METER voltage outputs.
Figure 5 shows a typical setup for the ADE7878 evaluation The evaluation board is connected to the PC using a regular
board. In this example, an energy meter for a 4 wire, three phase USB cable supplied with the board. When the evaluation board
distribution system is shown. Current transformers are used to has been powered up and is connected to the PC, the
sense the phase and neutral currents and are connected as enumeration process begins and the PC recognizes new
shown in Figure 5. The line voltages are connected directly to hardware and asks to install the appropriate driver. The driver
the evaluation board as shown. Note the state of all jumpers is found in VirCOM_Driver_XP folder of the CD. After the
must match the indication in Figure 5 and the fact the board is driver has been installed, the supplied evaluation software can
supplied from two different 3.3V power supplies, one for the be launched. The next section describes the ADE7878
ADE7878 domain, VDD, and one for LPC2368 domain, evaluation software in detail and how it can be installed and
MCU_VDD. As the two domains are isolated to ensure there is uninstalled.
no electrical connection between the high voltage test circuit
MCU_GND
MCU_VDD
GND
VDD
Phase C
P9 P12
P1
Neutral
R1
IAN JP3A, JP4A = closed
R2
IAN JP5A, JP6A = open
P2
IBP R3 IBP JP1B, JP2B = open
C32
P7
VBP R27 R30
VBP
JP7B, JP8B = open
R33
C33
P6
VCP R28 R31
VCP
JP7C, JP8C = open
R34
C34
Load
P5
VN R25
VN
JP7N, JP8N = open
C34
Neutral
Figure 11. CFx Configuration panel Figure 14. Fundamental Active Power panel
Apparent Power
Figure 12. Read Energy Registers panel
When “Apparent Power” is selected, a new panel is opened
(Figure 16). Similar to the other panels that deal with power
measurement, this panel is divided in two horizontal halfs: the
one below shows the apparent power data path of one phase
Power Quality
Power Quality panel is divided in two horizontal halfs. The
bottom one shows various registers that manage various power
quality measurements function of Active Measurement button.
The one above shows ADE7878 status and various buttons that
manage the measurements. When “Read Configuration” button
is pressed, all power quality registers (MASK1[31:0],
STATUS1[31:0], PERIOD[15:0], MMODE[7:0], ISUM[27:0],
OVLVL[23:0], OILVL[23:0], PHSTATUS[15:0], IPEAK[31:0],
VPEAK[31:0], SAGLVL[23:0], SAGCYC[7:0], ANGLE0[15:0],
ANGLE1[15:0], ANGLE2[15:0], COMPMODE[15:0],
CHECKSUM[31:0], PEAKCYC[7:0]) are read and the ones
belonging to the active window are visualized. Based on
PERIOD[15:0] register, the line frequency is computed and Figure 20. Zero Crossing Measurements panel
visualized in the Zero Crossing Measurement window. Based on
Figure 21. Neutral Current Mismatch panel Figure 24. Time Intervals Between Phases panel
Waveform Sampling
This panel (see Figure 25) uses HSDC port to acquire data from
the ADE7878 and visualize it. It can be accessed only if the
communication between ADE7878 and LPC2368 is I2C. See
Activating Serial Communication ADE7878 − LPC2368 section
for details on how to set I2C communication on the ADE7878
evaluation board.
The HSDC transmits data to LPC2368 at 4MHz because this is
the maximum speed the slave SPI of LPC2368 can receive data.
The panel contains some switches that must be set before
acquiring data:
-One switch chooses what quantities are visualized: phase
currents and voltages or phase powers. For every set of
quantities, only two can be acquired at a time. This choice is
done using the buttons “Select Waveform1” and “Select
Figure 22. Overvoltage & Overcurrent management panel Waveform2”.
-A second switch allows for acquired data to be stored in files
for further utilization.
-The acquisition time should also be set before an acquisition is
ordered. By default, this time is 150msec. It is limited for phase
currents and voltages for up to 1sec, but for phase powers is
unlimited. This difference appears because the LPC2368 must
execute in real time three tasks using the ping pong buffer
method: continuously receiving data from HSDC, storing it into
its USB memory, sending it to the PC. More time it takes the
HSDC to transmit data, more time LPC2368 has to transmit
data to the PC. As transmitting 6 phase currents and voltages at
4MHz takes 103.25μsec, less than 125 μsec, but transmitting 9
phase powers takes 133.25μsec, more than 125 μsec, the first
quantities are transmitted by HSDC at 8KHz update rate and
the second at 4KHz rate. This means the phase currents and
voltages can be acquired only for up to 1sec before the LPC2368
Figure 23. Peak management panel goes out of bandwidth and the powers can be acquired for an
unlimited time.
CHECKSUM Register
This panel gives access to all ADE7878 registers that are used to
compute CHECKSUM[31:0] register (see Figure 26). The user
can read/write the value of these registers by clicking on
“Read”/”Write” buttons. LabView program estimates the value
of CHECKSUM[31:0] register and visualizes it whenever one of
the registers is changed. When “Read” button is pressed, aside
from reading the registers, CHECKSUM[31:0] is also read and
visualized. In this way, the user can compare the value of
CHECKSUM[31:0] estimated by LabView with the value read
from ADE7878. They should always be identical.
NOTES