EVAL-ADE7816EBZ AD [Analog Devices], EVAL-ADE7816EBZ Datasheet - Page 25

• Manufacturer Part Number: EVAL-ADE7816EBZ
• Description: Six Current Channels, One Voltage Channel
• Manufacturer: AD [Analog Devices]

Data Sheet
ENERGY PHASE CALIBRATION
The
transducers, including those that induce inherent phase errors.
A phase error of 0.1° to 0.3° is not uncommon for a current
transformer (CT). These phase errors can vary from part to
part, and they must be corrected to achieve accurate power
readings. The errors associated with phase mismatch are
particularly noticeable at low power factors. The
provides a means of digitally calibrating these small phase
errors by introducing a time delay or a time advance.
Because different sensors can be used on each channel, sepa-
rate phase calibration registers are included all six channels.
The PCF_A_COEFF register (Address 0x43B1) can be used to
correct phase errors on Current Channel A. The PCF_B_COEFF
(Address 0x43B2), PCF_C_COEFF (Address 0x43B3), PCF_D_
COEFF (Address 0x43B4), PCF_E_COEFF (Address 0x43B5),
and PCF_F_COEFF (Address 0x43B6) registers control the phase
calibration on the B through F current channels, respectively. All
registers are 24-bit, unsigned.
The
and delays to the current channels with respect to the voltage
channels. A separate filter is included on each of the six current
channels. To adjust the time delay or advance, the coefficient of
these filters must be adjusted. Equation 12, Equation 13, and
Equation 14 show how the coefficients correspond to the phase
offset in radians.
If PCF_x_COEFF ≥ 0, then
If PCF_x_COEFF < 0, then
where θ is the required current-to-voltage phase adjustment.
ADE7816
ADE7816
PCF_x_COEFF
PCF_x_COEFF = 2
PCF_x_COEFF = (2
ω
=
2
π
Linefreq
uses all pass filters to accurately add time advances
is designed to function with a variety of current
8000
FRACTION
(
Hz
23
23
× PCF_x_COEFF
)
+ 23
=
sin(
28
) × PCF_x_COEFF
θ
sin(
+
θ
3
ω
+
)
4
−
ω
sin
FRACTION
)
ω
ADE7816
FRACTION
(12)
(13)
(14)
Rev. 0 | Page 25 of 48
To simplify this calculation, Analog Devices has a spreadsheet
file that calculates this value. To obtain this spreadsheet, contact
a representative of Analog Devices.
By default, the PCF_x_COEFF registers are set to 0. This setting
does not, however, result in a 0° phase shift. On startup, the
PCF_x_COEFF registers should be set to 0x400C4A for a 50 Hz
system and 0x401235 for a 60 Hz system.
RMS OFFSET CALIBRATION
The
each channel, as follows: IARMSOS (Address 0x438B), IBRMSOS
(Address 0x438C), ICRMSOS (Address 0x438D), IDRMSOS
(Address 0x438E), IERMSOS (Address 0x438F), IFRMSOS
(Address 0x4390), and VRMSOS (Address 0x438A). These 24-bit,
signed registers are used to remove offsets in the current and
voltage rms calculations. The rms offset compensation register
is added to the squared current and voltage signal before the
square root is executed. Equation 15 shows the relationship
between the rms measurement and the offset adjustment.
where I
measurement, respectively, without offset correction.
ADE7816
V
I
rms
rms
rms 0
=
=
and V
V
I
includes an rms offset compensation register for
rms
rms
rms 0
2
0
2
0
+
+
are the current and voltage rms
128
128
×
×
VRMSOS
IxRMSOS
ADE7816
(15)