EVAL-ADE7752EB datasheet(19/24 Pages) AD

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ADE7752/ADE7752A

Rev. C | Page 19 of 24

MODE SELECTION OF THE SUM OF THE THREE

ACTIVE ENERGIES

The ADE7752 can be configured to execute the arithmetic sum

of the three active energies, Wh = WhϕA + WhϕB + WhϕC, or the

sum of the absolute value of these energies, Wh = |WhϕA| +

|WhϕB| + |WhϕC|. The selection between the two modes can be

made by setting the ABS pin. Logic high and logic low applied

on the ABS pin correspond to the arithmetic sum and the sum

of absolute values, respectively.

When the sum of the absolute values is selected, the active

energy from each phase is always counted positive in the total

active energy. It is particularly useful in 3-phase 4-wire installa-

tion where the sign of the active power should always be the

same. If the meter is misconnected to the power lines, (for

instance, if CT is connected in the wrong direction), the total

active energy recorded without this solution can be reduced by

two-thirds.

The sum of the absolute values assures that the active energy

recorded represents the actual active energy delivered. In this

mode, the reverse power pin still detects when negative power is

present on any of the three phase inputs.

POWER MEASUREMENT CONSIDERATIONS

Calculating and displaying power information always has some

associated ripple that depends on the integration period used in

the MCU to determine average power as well as the load. For

example, at light loads, the output frequency may be 10 Hz.

With an integration period of 2 seconds, only about 20 pulses

are counted. The possibility of missing one pulse always exists

since the ADE7752 output frequency is running asynchro-

nously to the MCU timer. This would result in a 1-in-20 or

5% error in the power measurement.

EVAL-ADE7752EB 데이터시트(PDF) 19 Page - Analog Devices