ADE7763ARSZ datasheet(31/56 Pages) AD

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Data Sheet

ADE7763

Rev. C | Page 31 of 56

LINE CYCLE ENERGY ACCUMULATION MODE

In line cycle energy accumulation mode, the energy accumu-

lation of the ADE7763 can be synchronized to the Channel 2

zero crossing so that active energy accumulates over an integral

number of half line cycles. The advantage of summing the active

energy over an integral number of line cycles is that the

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

eliminates ripple in the energy calculation. Energy is calculated

more accurately and in a shorter time because the integration

period is 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 ADE7763 is placed in line cycle energy accumulation mode

by setting Bit 7 (CYCMODE) in the mode register. In line cycle

energy accumulation mode, the ADE7763 accumulates the

active power signal in the LAENERGY register (Address 0x04)

for an integral number of line cycles, as shown in Figure 61. The

number of half line cycles is specified in the LINECYC register

(Address 0x1C). The ADE7763 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, the CYCEND

flag in the interrupt status register is set (Bit 2) at the end of a

line cycle energy accumulation cycle. If the CYCEND enable bit

in the interrupt enable register is enabled, the IRQ output also

will go active low. Therefore, the 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,















































)

cos(

)

(



(20)

where:

n is an integer.

T is the line cycle period.

Since the sinusoidal component is integrated over an integral

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

 



VIdt

(21)



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 of 65,535 half line cycles. At 60 Hz line

frequency, this translates to a total duration of 65,535/

120 Hz = 546 seconds.

POSITIVE-ONLY ACCUMULATION MODE

In positive-only accumulation mode, the active energy

accumulation is only done for positive power, ignoring any

occurrence of negative power above or below the no-load

threshold, as shown in Figure 62. The CF pulse also reflects this

accumulation method when in this mode. Positive-only

accumulation mode is activated by setting the MSB of the mode

default setting for this mode is off. 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 PPOS and PNEG

bits are set in the interrupt enable register. The corresponding

PPOS and PNEG bits in the interrupt status register show

which transition has occurred—see the register descriptions in

Table 9.

PNEG

PPOS

INTERRUPT STATUS REGISTERS

PPOS

PNEG

IRQ

NO-LOAD

THRESHOLD

ACTIVE POWER

NO-LOAD

THRESHOLD

ACTIVE ENERGY

Figure 62. Energy Accumulation in Positive-Only Accumulation Mode

NO-LOAD THRESHOLD

The ADE7763 includes a no-load threshold feature on the

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

is accomplished because energy does not accumulate 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 0.0167% of the full-scale

output frequency of the multiplier.

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