ade7880 Analog Devices, Inc., ade7880 Datasheet - Page 60

• Manufacturer Part Number: ade7880
• Description: Polyphase Multifunction Energy Metering Ic With Harmonic Monitoring
• Manufacturer: Analog Devices, Inc.

ADE7880
The harmonic distortions of the 3 harmonic components are
stored into HXVHD, HXIHD, HYVHD, HYIHD, HZVHD,
HZIHD 24-bit registers in 3.21 signed format. This means the
ratios are limited to +3.9999 and all greater results are clamped
to it.
As a reference, Table 20 presents the ADE7880 harmonic
engine outputs when one phase is analyzed and the registers in
which the outputs are stored.
Harmonic calculations when the neutral is monitored
When the neutral current and the sum of phase currents are
monitored, only the harmonic rms related registers are updated.
The registers HX, HY and HZ identify the index of the
harmonic, including the fundamental. When a phase is
analyzed, the fundamental rms values are calculated
continuously and the results are stored in dedicated registers
FIRMS and FVRMS. When the neutral is analyzed, the
fundamental information is calculated by setting one of the
harmonic index registers HX, HY or HZ to 1 and the results are
stored in harmonic registers. The maximum index allowed in
HX, HY and HZ registers is 63. The no attenuation pass band is
2.8KHz, corresponding to a -3dB bandwidth of 3.3KHz, thus all
CALCULATIONS
COMPONENTS
HARMONIC
Figure 61. Harmonic active and reactive powers signal processing
HPGAIN
HPGAIN
HPGAIN
HPGAIN
HPGAIN
HPGAIN
Rev. PrE | Page 60 of 103
harmonics of frequency lower than 2800Hz are supported
without attenuation.
HXIRMS, HYIRMS and HZIRMS registers contain the
harmonic rms components of the neutral current and
HXVRMS, HYVRMS and HZVRMS registers contain the
harmonic rms components of ISUM. Note that in this case, the
rms of the fundamental component is not computed into
FIRMS or FVRMS registers, but it is computed if one of the
index registers HX, HY and HZ is initialized with 1. As a
reference, Table 21 presents the ADE7880 harmonic engine
outputs when the neutral current and ISUM are analyzed and
the registers in which the outputs are stored.
Configuring harmonic calculations update rate
The ADE7880 harmonic engine functions at 8 KHz rate. From
the moment the HCONFIG register is initialized and the
harmonic indexes are set in the HX, HY and HZ index registers,
the ADE7880 calculations take typically 750 msec to settle
within the specification parameters.
The update rate of the harmonic engine output registers is
managed by bits 7:5 (HRATE) in HCONFIG register and is
independent of the engine’s calculations rate of 8 KHz. The
HXWATTOS
HYWATTOS
HZWATTOS
HXVAROS
HYVAROS
HZVAROS
Σ
Σ
Σ
Σ
Σ
Σ
2
2
2
2
2
2
2
2
2
2
2
2
Preliminary Technical Data
HXWATT
HYWATT
HZWATT
HXVAR
HYVAR
HZVAR