ADE7753ARS datasheet(33/60 Pages) AD

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ADE7753

Rev. C | Page 33 of 60

LINE CYCLE ENERGY ACCUMULATION MODE

In line cycle energy accumulation mode, the energy accumula-

tion of the ADE7753 can be synchronized to the Channel 2 zero

crossing so that active energy can be accumulated over an

integral number of half line cycles. The advantage of summing

the active energy over an integer number of line cycles is that

the sinusoidal component in the active energy is reduced to 0.

This eliminates any ripple in the energy calculation. Energy is

calculated more accurately and in a shorter time because the

integration period can be shortened. By using the line cycle

energy accumulation mode, the energy calibration can be

greatly simplified, and the time required to calibrate the meter

can be significantly reduced. The ADE7753 is placed in line

cycle energy accumulation mode by setting Bit 7 (CYCMODE)

in the mode register. In line cycle energy accumulation mode,

the ADE7753 accumulates the active power signal in the

LAENERGY register (Address 0x04) for an integral number of

line cycles, as shown in Figure 69. The number of half line

cycles is specified in the LINECYC register (Address 0x1C). The

ADE7753 can accumulate active power for up to 65,535 half

line cycles. Because the active power is integrated on an integral

number of line cycles, at the end of a line cycle energy accumu-

lation cycle the CYCEND flag in the interrupt status register is

set (Bit 2). If the CYCEND enable bit in the interrupt enable

IRQ line can also be used to signal the completion of the line

cycle energy accumulation. Another calibration cycle can start

as long as the CYCMODE bit in the mode register is set.

From Equations 13 and 18,

E(t) =

∫

⎪

⎭

⎪

⎬

⎫

⎪

⎩

⎪

⎨

⎧

⎟

⎠

⎞

⎜

⎝

⎛

−

cos

(2πft)dt

(20)

where:

n is an integer.

T is the line cycle period.

Since the sinusoidal component is integrated over an integer

number of line cycles, its value is always 0. Therefore,

E =

+ 0

(21)

∫

VIdt

E(t) = VInT

(22)

Note that in this mode, the 16-bit LINECYC register can hold a

maximum value of 65,535. In other words, the line energy

accumulation mode can be used to accumulate active energy for

a maximum duration over 65,535 half line cycles. At 60 Hz line

frequency, it translates to a total duration of 65,535/120 Hz =

546 seconds.

POSITIVE-ONLY ACCUMULATION MODE

In positive-only accumulation mode, the energy accumulation

is done only for positive power, ignoring any occurrence of

negative power above or below the no-load threshold, as shown

in Figure 70. The CF pulse also reflects this accumulation

method when in this mode. The ADE7753 is placed in positive-

only accumulation mode by setting the MSB of the mode

Transitions in the direction of power flow, going from negative

to positive or positive to negative, set the IRQ pin to active low

if the interrupt enable register is enabled. The interrupt status

registers, PPOS and PNEG, show which transition has

occurred—see the ADE7753 register descriptions in

Table 12

PNEG

PPOS

INTERRUPT STATUS REGISTERS

PPOS

PNEG

IRQ

NO-LOAD

THRESHOLD

ACTIVE POWER

NO-LOAD

THRESHOLD

ACTIVE ENERGY

02875-0-069

Figure 70. Energy Accumulation in Positive-Only Accumulation Mode

NO-LOAD THRESHOLD

The ADE7753 includes a no-load threshold feature on the

active energy that eliminates any creep effects in the meter. The

ADE7753 accomplishes this by not accumulating energy if the

multiplier output is below the no-load threshold. This threshold

is 0.001% of the full-scale output frequency of the multiplier.

Compare this value to the IEC1036 specification, which states

that the meter must start up with a load equal to or less than

0.4% Ib. This standard translates to .0167% of the full-scale

output frequency of the multiplier.

REACTIVE POWER CALCULATION

Reactive power is defined as the product of the voltage and

current waveforms when one of these signals is phase-shifted by

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