Datasheet

Data Sheet ADE7880
Rev. A | Page 58 of 104
IA, VA
IB, VB
IC, VC
IN, ISUM
HXWATT
HYWATT
HZWATT
FWATT
HXVAR
HYVAR
HZVAR
FVAR
HXVA
HYVA
HZVA
FVA
HXVRMS
HYVRMS
HZVRMS
FVRMS
HXIRMS
HYIRMS
HZIRMS
FIRMS
HXVHD
HYVHD
HZVHD
VTHD
HXIHD
HYIHD
HZIHD
ITHD
HXPF
HYPF
HZPF
FPF
ADE7880 HARMONIC
CALCULATIONS
HXVRMS
HYVRMS
HZVRMS
HXIRMS
HYIRMS
HZIRMS
IN
RESULTS
ISUM
RESULTS
HXVHD
HYVHD
HZVHD
HXIHD
HYIHD
HZIHD
IN
RESULTS
ISUM
RESULTS
HPHASE BITS
HCONFIG[2,1]
SELECT THE PHASE
BEING MONITORED
OUTPUT REGISTERS USED WHEN ONE OF PHASES A, B, C IS ANALYZED
ACTPHSEL BITS HCONFIG[9,8] SELECT
THE PHASE USED TO AS TIME BASE
HX, HY, HZ REGISTERS SELECT THE
HARMONICS TO MONITOR
HRATE BITS HCONFIG[7:5] SELECT THE
UPDATE RATE OF HARMONIC
REGISTERS
HSTIME BITS HCONFIG[4,3] SELECT
THE DELAY IN TRIGGERING HREADY
INTERRUPT
HRCFG BIT HCONFIG[0] SELECTS IF
HREADY FLAG IN STATUS0 IS SET
IMMEDIATELY OF AFTER HSTIME
OUTPUT REGISTERS
USED WHEN NEUTRAL
CURRENT IS ANALYZED
10193-057
Figure 82. ADE7880 Harmonic Engine Block Diagram
When the neutral current and the sum of the three phase
currents represented by ISUM register are analyzed, the
following metering quantities are computed for both currents:
• RMS of fundamental and of up to 2 harmonics or rms of
up to three harmonics: I
x
, I
y
, I
z
, x, y, z = 1,2, 3,…, N.
• Harmonic distortions of the analyzed harmonics.
Configuring the Harmonic Calculations
The ADE7880 requires a time base provided by a phase voltage.
Bit 9 and Bit 8 (ACTPHSEL) of HCONFIG[15:0]register select
this phase voltage. If ACTPHSEL = 00, the phase A is used. If
ACTPHSEL = 01, the Phase B is used and if ACTPHSEL = 10,
the Phase C is used. If the phase voltage used as time base is
down, select another phase, and the harmonic engine continues
to work properly.
The phase under analysis is selected by Bit 2 and Bit 1
(HPHASE) of HCONFIG[15:0]register. If HPHASE = 00, the
Phase A is monitored. If HPHASE = 01, the Phase B is
monitored and if HPHASE = 10, the Phase C is monitored. If
HPHASE = 11, the neutral current together with the sum of the
phase currents represented by ISUM register are monitored.
Harmonic Calculations When a Phase is Monitored
When a phase is monitored, fundamental information together
with information about up to three harmonics is computed. The
indexes of the three additional harmonics simultaneously
monitored by the ADE7880 are provided by the 8-bit registers
HX, HY, and HZ. Simply write the index of the harmonic into
the register for that harmonic to be monitored. If the second
harmonic is monitored, write 2. If harmonic 51 is desired, write
51. The fundamental components are always monitored,
independent of the values written into HX, HY, or HZ.
Therefore, if one of these registers is made equal to 1, the
ADE7880 monitors the fundamental components multiple times.
The maximum index allowed in HX, HY, and HZ registers is 63.
The no attenuation pass band is 2.8 kHz, corresponding to a −3
dB bandwidth of 3.3 kHz, thus all harmonics of frequency lower
than 2800 Hz are supported without attenuation.
The rms of the phase voltage and phase current fundamental
components are stored into FVRMS and FIRMS 24-bit signed
registers. The associated data path is presented in Figure 83.
Similar to the rms current and voltage rms data paths presented
in Root Mean Square Measurement section, the data path
contains 24-bit signed offset compensation registers xIRMSOS,
xVRMSOS, x = A, B, C for each phase quantity. The rms of the
phase current and phase voltage three harmonic components
are stored into HXVRMS, HXIRMS, HYVRMS, HYIRMS,
HZVRMS, and HZIRMS 24-bit signed registers. The associated
data path is presented in Figure 84 and contains the following
24-bit signed offset compensation registers: HXIRMSOS,
HYIRMSOS, HZIRMSOS, HXVRMSOS, HYVRMSOS, and
HZVRMSOS.
It is recommended to leave the offset compensation registers at
0, the default value.