ADE7752B datasheet(21/27 Pages) AD

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Preliminary Technical Data

ADE7752B

Rev. PrA | Page 21 of 27

POWER MEASUREMENT CONSIDERATIONS

Calculating and displaying power information always have 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 can be 10 Hz. With an integra-

tion period of two seconds, only about 20 pulses are counted. The

possibility of missing one pulse always exists since the ADE7752B

output frequency is running asynchronously to the MCU timer.

This would result in a 1-in-20 or 5% error in the power measure-

ment. To remedy this, an appropriate integration time should be

considered to achieve the desired accuracy.

MODE SELECTION OF THE SUM OF THE THREE

ACTIVE ENERGIES

The ADE7752B 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

instillation where the sign of the active power should always be

the same. If the meter is misconnected to the power lines, that

is, CT connected in the wrong direction then 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.

Regardless of the mode selected using this pin, the reverse

power pin still detects when negative power is present on the

sum of the three phase inputs.

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