ADE7754ARRL datasheet(21/44 Pages) AD

21 / 44 page

REV. PrG 01/03

PRELIMINARY TECHNICAL DATA

ADE7754

– 21 –

Reverse Power Information

The ADE7754 detects when the current and voltage channels

of any of the three phase inputs have a phase difference greater

than 90° i.e.

|Φ

A| or

|Φ

B| or

|Φ

C| > 90°. This mechanism can

detect wrong connection of the meter or generation of Active

Energy.

The Reverse power information is available for Phase A - B

and C respectively by reading bit12-14 of the CFNUM

sign of the active power of the corresponding phase. Logic

one corresponds to negative active power.

The AENERGY phase selection bits (WATSEL bits of the

WATMode register) enable the negative power detection per

phase. If Phase A is enabled in the AENERGY accumulation

-bit 5 of WATMode register sets to logic one- the negative

power detection for Phase A -bit 12 of CFNUM register-

indicates the direction of the active energy. If Phase A is

disabled in the AENERGY register, the negative power bit

for Phase A is set to logic zero.

TOTAL ACTIVE POWER CALCULATION

The sum of the active powers coming from each phase gives

the total active Power consumption. Different combinations

of the three phases can be selected in the sum by setting bits

7-6 of the WATMode register (mnemonic WATMOD[1:0]).

Figure 24 demonstrates the calculation of the total active

power.

The total active power calculated by the ADE7754 depends

on the configuration of the WATMOD bits in the WATMode

by setting WATSEL bits respectively to logic 0 or logic 1 in

the WATMode register. The different configurations are

described in Table I.

WATMOD

WATSEL0

WATSEL1

WATSEL2

VA x IA

+ VB x IB

+ VC x IC

VA x (IA

*-I

*)+ 0

+ VC x (IC

*-I

VA x (IA

*-I

*)+ 0

+ VC x IC

Table I -Total Active Power calculation

Note: IA

*, I

* and I

* represent the current channels samples

after APGAIN correction and High-Pass Filtering.

For example, for WATMOD = 1, when all the gains and

offsets corrections are taken into consideration, the exact

formula that is used to process the Active Power is:

Total Active Power

AAPGAIN

BAPGAIN

⋅+









⋅−









⋅

















⋅+









+⋅





AAPOS

AWG

CAPGAIN





⋅−









⋅

















⋅+





BAPGAIN

ICAPOS

CWG







Depending on the polyphase meter service, the appropriate

formula should be chosen to calculate the Active power. The

American ANSI C12.10 standard defines the different con-

figurations of the meter. Table II describes which mode

should be chosen in these different configurations.

ANSI Meter Form

WATMOD

WATSEL

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

Table II - Meter form configuration

Different gain calibration parameters are offered in the

ADE7754 to cover the calibration of the meter in different

configurations. It should be noticed that in Mode 0, APGAIN

and WGAIN registers have the same effect on the end result.

In this case, APGAIN registers should be set at their default

value and the gain adjustment should be done with the

WGAIN registers.

PHASE A*

LPF2

HPF

BAPGAIN

BWGAIN

Total Instantaneous

Power Signal

Active Power

Signal - P

2752545h

PHASE B*

HPF

LPF2

CAPGAIN

CWGAIN

PHASE C*

HPF

LPF2

AAPGAIN

AWGAIN

AAPOS

BAPOS

CAPOS

Figure 24 –Total Active Power Consumption Calculation

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