ADE7754_15 datasheet(25/44 Pages) AD

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REV. 0

ADE7754

–25–

and voltage gain registers. See the Current RMS Calculation

and Voltage RMS Calculation sections. Only the effect of the

apparent power gain is shown on Figure 35. The minimum

output range is given when the apparent power gain register

content is equal to 800h and the maximum range is given by

writing 7FFh to the apparent power gain register. This can be

used to calibrate the apparent power (or energy) calculation

in the ADE7754 for each phase and the total apparent energy.

See the Total Apparent Power Calculation section.

00000h

D1B71h

+ 100% FS

– 100% FS

F2E48Fh

+ 150% FS

+ 50% FS

– 50% FS

– 150% FS

13A929h

68DB9h

F97247h

EC56D7h

AVAGAIN[11:0]

000h

7FFh 800h

APPARENT

POWER

VOLTAGE CHANNEL AND

CURRENT CHANNEL 0.5V/GAIN

Figure 35. Apparent Power Calculation Output Range

Apparent Power Offset Calibration

Each rms measurement includes an offset compensation register

to calibrate and eliminate the dc component in the rms value.

See the Current RMS Calculation and Voltage RMS Calculation

sections. The voltage and current rms values are then multiplied

in the apparent power signal processing. Because no additional

offsets are created in the multiplication of the rms values, there

is no specific offset compensation in the apparent power signal

processing. The offset compensation of the apparent power

measurement in each phase is done by calibrating each indi-

vidual rms measurement.

TOTAL APPARENT POWER CALCULATION

The sum of the apparent powers coming from each phase gives

the total apparent power consumption. Different combinations

of the three phases can be selected in the sum by setting Bits 7

and 6 of the VAMode register (mnemonic VAMOD[1:0]). Figure 36

demonstrates the calculation of the total apparent power.

RMS

AAPGAIN

RMS

AVAGAIN

VARMS

AVGAIN

PHASE A

RMS

CAPGAIN

RMS

CVAGAIN

VCRMS

CVGAIN

PHASE C

RMS

BAPGAIN

RMS

BVAGAIN

BVGAIN

PHASE B

VARMS

VCRMS

TOTAL APPARENT

POWER SIGNAL

Figure 36. Total Apparent Power Calculation

The total apparent power calculated by the ADE7754 depends on

the configuration of the VAMOD bits in the VAMode register.

Each term of the formula used can be disabled or enabled by the

setting VASEL bits, respectively, to Logic 0 or Logic 1 in the

VAMode register. The different configurations are described in

Table IV.

Table IV. Total Apparent Power Calculation

VAMOD VASEL0

VASEL1

VASEL2

VARMS

× I

ARMS

+ VBRMS

× I

BRMS

+ VCRMS

× I

CRMS

VARMS

× I

ARMS

+(VARMS + VCRMS)

IBRMS

+ VCRMS

× I

CRMS

VARMS

× I

ARMS

+ VARMS

× I

BRMS

+ VCRMS

× I

CRMS

Note that VARMS, VBRMS, VCRMS, IARMS, IBRMS, and ICRMS represent

the voltage and current channels RMS values of the corresponding

registers.

For example, for VAMOD = 1, the formula used to process the

apparent power is

Total Apparent Power

AVAG

BVAG

CVAG

ARMS

CRMS

BRMS

CRMS

=×

× +









×× +









+×

× +









()

The polyphase meter configuration determines which formula

should be used to calculate the apparent energy. The American

ANSI C12.10 standard defines the different configurations of

the meter. Table V describes which mode should be chosen for

different configurations.

Table V. Meter Form Configuration

ANSI

Meter Form

VAMOD

VASEL

5S/13S

3-wire Delta

3 or 5 or 6

6S/14S

4-wire Wye

8S/15S

4-wire Delta

9S/16S

4-wire Wye

Different gain calibration parameters are offered in the ADE7754

to cover the calibration of the meter in different configurations.

The APGAIN, VGAIN, and VAGAIN registers have different

purposes in the signal processing of the ADE7754. APGAIN

registers affect the apparent power calculation but should be

used only for active power calibration. VAGAIN registers are

used to calibrate the apparent power calculation. VGAIN regis-

ters have the same effect as VAGAIN registers when VAMOD =

0 or 2. They should be left at their default value in these modes.

VGAIN registers should be used to compensate gain mismatches

between channels in VAMOD = 1.

As mentioned previously, the offset compensation of the phase

apparent power calculation is done in each individual rms mea-

surement signal processing. See the Apparent Power Offset

Calibration section.

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