ADE5166 datasheet(55/148 Pages) AD

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ADE5166/ADE5169

Rev. 0 | Page 55 of 148

ACTIVE ENERGY CALCULATION

As stated in the Active Power Calculation section, power is

defined as the rate of energy flow. This relationship can be

expressed mathematically, as shown in Equation 11.

∫

)

(

⎭

⎬

⎫

⎩

⎨

⎧

∑

∫

∞

→

)

(

lim

)

(

(11)

The active energy accumulation depends on the setting of

POAM (Bit 1) and ABSAM (Bit 0) in the ACCMODE register

(Address 0x0F). When both bits are cleared, the addition is signed

and, therefore, negative energy is subtracted from the active

energy contents. When both bits are set, the ADE5166/ADE5169

are set to be in the more restrictive mode, the positive-only

accumulation mode.

where:

P is power.

E is energy.

Conversely, energy is given as the integral of power.

(12)

When POAM (Bit 1) in the ACCMODE register (Address 0x0F)

is set, only positive power contributes to the active energy accumu-

lation. When ABSAM (Bit 0) in the ACCMODE register

(Address 0x0F) is set, the absolute active power is used for the

active energy accumulation (see the Watt-Absolute Accumulation

Mode section).

The ADE5166/ADE5169 achieve the integration of the active

power signal by continuously accumulating the active power signal

in an internal, nonreadable, 49-bit energy register. The register

(WATTHR[23:0], Address 0x01) represents the upper 24 bits

of this internal register. This discrete time accumulation or

summation is equivalent to integration in continuous time.

Equation 13 expresses the relationship.

(13)

The output of the multiplier is divided by the value in the WDIV

to 0, the internal active energy register is divided by 1. WDIV is an

8-bit, unsigned register. After dividing by WDIV, the active energy

is accumulated in a 49-bit internal energy accumulation register.

The upper 24 bits of this register are accessible through a read

to the active energy register (WATTHR[23:0], Address 0x01).

A read to the RWATTHR register (Address 0x02) returns the

contents of the WATTHR register, and the upper 24 bits of the

internal register are cleared. As shown in Figure 61, the active

power signal is accumulated in an internal 49-bit signed register.

The active power signal can be read from the waveform register

by setting the WAVMODE register (Address 0x0D) and setting

the WFSM bit (Bit 5) in the Interrupt Enable 3 SFR (MIRQENH,

Address 0xDB). Like the current and voltage channels waveform

sampling modes, the waveform data is available at sample rates of

25.6 kSPS, 12.8 kSPS, 6.4 kSPS, and 3.2 kSPS.

where:

n is the discrete time sample number.

T is the sample period.

The discrete time sample period (T) for the accumulation

addition to calculating the energy, this integration removes any

sinusoidal components that may be in the active power signal.

Figure 61 shows this discrete time integration or accumulation.

The active power signal in the waveform register is continuously

added to the internal active energy register.

WGAIN[11:0]

WDIV[7:0]

LPF2

CURRENT

CHANNEL

VOLTAGE

CHANNEL

TIME (nT)

MCLK

ACTIVE POWER

SIGNAL

WATTHR[23:0]

OUTPUTS FROM THE LPF2 ARE

ACCUMULATED (INTEGRATED) IN

THE INTERNAL ACTIVE ENERGY REGISTER

UPPER 24 BITS ARE

ACCESSIBLE THROUGH

WATTHR[23:0] REGISTER

FOR WAVEFORM

SAMPLING

WATTOS[15:0]

sgn

2–6 2–7 2–8

DIGITAL-TO-FREQUENCY

CONVERTER

WAVEFORM

VALUES

Figure 61. Active Energy Calculation

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