ADE7762_15 datasheet(22/28 Pages) AD

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ADE7762

Rev. 0 | Page 22 of 28

ACCUMULATION OF 3-PHASE POWER

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 integration period of 2 seconds, only about

20 pulses are counted. The possibility of missing one pulse

always exists because the ADE7762 output frequency is running

asynchronously to the MCU timer. This results in a 1-in-20

or 5% error in the power measurement. 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 ADE7762 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, that is,

if CT is 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. In this

mode, the reverse power pin still detects when the arithmetic

sum of the active powers is negative, but energy continues to

accumulate regardless of the sign.

Negative Total Power Detection

The ADE7762 detects when total power, calculated as the

arithmetic sum of the three phases, is negative. This detection

is independent of the mode of the sum of the three powers

(arithmetic or absolute). This mechanism can detect an incor-

rect connection of the meter or generation of negative active

energy. When the sum of the powers of the three phases is

negative, the REVP pin output goes active high. When the

sum of the powers of the three phases is positive, the REVP

pin output is reset to low.

The REVP pin output changes state at the same time that a

pulse is issued on CF. If the sum of the powers of the three

phases is negative, then the REVP pin output stays high until

the sum of the three phases’ power is positive or until all three

phases are below the no-load threshold.

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