ADE7166 datasheet(60/148 Pages) AD

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ADE75xx/ADE71xx

Preliminary Technical Data

Rev. PrE | Page 60 of 148

maintained at 0 when no power is being consumed.

The 256 LSBs (VAROS = 0x100) written to the reactive power

offset register are equivalent to 1 LSB in the waveform sample

Sign of Reactive Power Calculation

Note that the average reactive power is a signed calculation. The

phase shift filter has –90° phase shift when the integrator is

enabled, and +90° phase shift when the integrator is disabled.

Table 42 summarizes the relationship between the phase differ-

ence between the voltage and the current and the sign of the

resulting VAR calculation.

Table 42. Sign of Reactive Power Calculation

Angle

Integrator

Sign

Between 0° to 90°

Off

Positive

Between –90° to 0°

Off

Negative

Between 0° to 90°

Positive

Between –90° to 0°

Negative

Reactive power sign detection

The ADE75XX/ADE71XX detects a change of sign in the

reactive power. A sign change can be monitored on the filtered

reactive power signal or on a per CF pulse basis, depending on

the configuration of the CFSIGN_OPT bit in the GAIN register

(0x1B). The VARSIGN flag in the Interrupt Status Register 1

SFR (MIRQSTL, 0xDC) record when a change of sign according

to bit VARSIGN in the ACCMODE register (0x0F) has

occurred. If the VARSIGN bit is set in the Interrupt Enable

ADE interrupt. The ADE interrupt stays active until the

VARSIGN status bit is cleared—see Energy measurement

interrupts section.

When VARSIGN in the ACCMODE register (0x0F) is cleared

(default), the VARSIGN flag in the Interrupt Status Register 1

SFR (MIRQSTL, 0xDC) will be set when a transition from

positive to negative reactive power has occurred.

When VARSIGN in the ACCMODE register (0x0F) is set, the

VARSIGN flag in the Interrupt Status Register 1 SFR

(MIRQSTL, 0xDC) will be set when a transition from negative

to positive reactive power has occurred.

Reactive power no-Load detection

The ADE75XX/ADE71XX includes a no-load threshold feature

on the reactive energy that eliminates any creep effects in the

meter. The ADE75XX/ADE71XX accomplishes this by not

accumulating reactive energy if the multiplier output is below

the no-load threshold. When the reactive power is below the

no-load threshold, the RNOLOAD flag in the Interrupt Status

set in the Interrupt Enable Register 1 SFR (MIRQENL, 0xD9),

the 8052 core has a pending ADE interrupt. The ADE interrupt

stays active until the RNOLOAD status bit is cleared—see

Energy measurement interrupts section.

The No-load threshold level is selectable by setting bits

RNOLOAD in the NLMODE register (0x0E). Setting these bits

to 0b00 disable the no-load detection and setting them to 0b01,

0b10 or 0b11 set the no-load detection threshold to 0.015%,

0.0075% and 0.0037% of the full-scale output frequency of the

multiplier respectively.

VARGAIN[11:0]

VARDIV[7:0]

LPF2

CURRENT

CHANNEL

VOLTAGE

CHANNEL

TIME (nT)

CLKIN

REACTIVE POWER

SIGNAL

VARHR[23:0]

OUTPUTS FROM THE LPF2 ARE

ACCUMULATED (INTEGRATED) IN

THE INTERNAL REACTIVE ENERGY REGISTER

UPPER 24 BITS ARE

ACCESSIBLE THROUGH

VARHR[23:0] REGISTER

WAVEFORM

VALUES

VAROS[15:0]

sgn

2-6 2-7 2-8

FOR WAVEF0RM

SAMPLING

HPF

90° PHASE

SHIFTING FILTER

PHCAL[7:0]

DIGITAL TO FREQUENCY

CONVERTER

Figure 45. ADE75XX/ADE71XX Reactive Energy Calculation

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