ADE9078ACPZ datasheet(41/108 Pages) AD

41 / 108 page

ADE9078

Data Sheet

Rev. 0 | Page 40 of 107

Energy Accumulation

Figure 61 shows how AWATT is accumulated into the AWATTHR

and AWATT_ACC registers. A no load threshold is applied and

the energy sign is checked to determine whether to accumulate

the AWATT sample into the internal energy accumulator. The

internal energy accumulator is either added to the AWATTHR

at a EGYRDY rate (see the Reloading or Accumulating User

Energy Register section for more details). The AWATT value is

directly accumulated into the internal power accumulator and

latched into AWATT_ACC at a PWRRDY rate. Set the

EGY_PWR_EN bit in EP_CFG register to run the energy and

power accumulator.

Signed Energy Accumulation Modes

Total Active Energy Accumulation Modes

In some installations, it is desirable to bill for only positive total

active energy. The ADE9078 offers a way to do so using the

WATTACC bits in the ACCMODE register. To set the total

active energy accumulation and any corresponding CF pulse

output for positive energy only, write 10 to WATTACC.

If WATTACC = 0, the energy accumulation is signed. The MSB

of the AWATTHR_HI register indicates whether the energy is

negative or positive.

Other accumulation modes include absolute accumulation

mode with WATTACC = 01, where the absolute value of

AWATT is accumulated, and negative only accumulation mode

with WATTACC = 11, where only negative active energy is

accumulated.

Reactive Energy Accumulation Modes

In some installations, because reactive energy may change

frequently between positive and negative values with inductive

and capacitive loads, it is desirable to bill for the absolute value

of reactive energy. The ADE9078 offers a way to do so using the

VARACC bits in the ACCMODE register. To set the total and

fundamental reactive energy register and any corresponding CF

pulse output to accumulate the absolute value of reactive

energy, write 01 to VARACC.

NO LOAD

CHECK

INTERNAL ENERGY

ACCUMULATOR

DIGITAL

FREQUENCY

CONVERTER

4.096MHz

AWATT

WATTACC[1:0]

ACT_NL_LVL

CHECK SIGN

TO DETERMINE

WHETHER

TO ACCUMULATE

ANOLOAD

EP_CFG.

NOLOAD_TMR

WTHR

CF1DEN

CF_LCFG

CFMODE

REVPSUMx

CFx

POWER

ENERGY

LOW-PASS

FILTERED

TOTAL ACTIVE

POWER

INTERNAL POWER ACCUMULATOR

fDSP

EGYRDY

031

AWATTHR_HI

EGY_LD_ACCUM

INTERNAL ENERGY ACCUMULATOR

VALUE ADDED TO AWATTHR

OR LATCHED INTO AWATTHR

AT EGYRDY RATE

PWRRDY

INTERNAL POWER ACCUMULATOR VALUE

LATCHED IN TO AWATT_ACC

WHEN PWR_TIMER SAMPLES

HAVE BEEN ACCUMULATED

fDSP

AWATTHR_LO

Figure 61. AWATT Accumulation into Energy and Power, Using No Load Threshold and Signed Accumulation Mode

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