EVAL-ADE7569F16EB datasheet(61/136 Pages) AD

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Preliminary Technical Data

ADE7566/ADE7569

Rev. PrA | Page 61 of 136

APPARENT ENERGY CALCULATION

The apparent energy is given as the integral of the apparent power.

∫

Power

Apparent

Energy

Apparent

)

(

(33)

The ADE7566/ADE7569 achieve the integration of the apparent

power signal by continuously accumulating the apparent power

signal in an internal 48-bit register. The apparent energy register

(VAHR[23:0]) represents the upper 24 bits of this internal

equivalent to integration in continuous time. Equation 34

expresses the relationship.

⎭

⎬

⎫

⎩

⎨

⎧

∑

∞

→

)

(

wer

ApparentPo

Lim

Energy

Apparent

(34)

where:

n is the discrete time sample number.

T is the sample period.

The discrete time sample period (T) for the accumulation

Figure 63 shows this discrete time integration or accumulation.

The apparent power signal is continuously added to the internal

energy theoretically remains positive.

The 49 bits of the internal register are divided by VADIV. If the

value in the VADIV register is 0, the internal apparent energy

The upper 24 bits are then written in the 24-bit apparent energy

provided to read the apparent energy. This register is reset to 0

after a read operation

Note that the apparent energy register is unsigned. By setting the

VAEHF and VAEOF bits in the Interrupt Enable Register 2 SFR

(MIRQENM, 0xDA), the ADE7566/ADE7569 can be configured

to issue an ADE interrupt to the 8052 core when the apparent

energy register is half-full or when an overflow occurs. The half-full

interrupt for the unsigned apparent energy register is based on

24 bits as opposed to 23 bits for the signed active energy register.

Integration Times Under Steady Load

As mentioned in the Apparent Energy Calculation section, the

discrete time sample period (T) for the accumulation register is

1.22 μs (5/MCLK). With full-scale sinusoidal signals on the

analog inputs and the VAGAIN register set to 0x000, the

average word value from the apparent power stage is 0x1A36E2

(see the Apparent Power Calculation section). The maximum

value that can be stored in the apparent energy register before it

overflows is 224 or 0xFF,FFFF. The average word value is added

to the internal register, which can store 248 or 0xFFFF,FFFF,FFFF

before it overflows. Therefore, the integration time under these

conditions with VADIV = 0 is calculated as follows:

Time =

min

sec

199

0xD055

FFFF

FFFF,

0xFFFF,

(35)

When VADIV is set to a value different from 0, the integration

time varies, as shown in Equation 36.

Time = TimeWDIV = 0 × VADIV

(36)

VADIV

APPARENT POWER

Irms

VAHR[23:0]

APPARENT POWER OR Irms IS

ACCUMULATED (INTEGRATED)

IN THE APPARENT ENERGY

TIME (nT)

APPARENT

POWER SIGNAL = P

Figure 63. Apparent Energy Calculation

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