ADE7763 datasheet(32/56 Pages) AD

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ADE7763

Rev. A | Page 32 of 56

APPARENT ENERGY CALCULATION

The apparent energy is given as the integral of the

apparent power.

∫

Power

Apparent

Energy

Apparent

)

(

(26)

The ADE7763 achieves the integration of the apparent power

signal by continuously accumulating the apparent power signal

in an internal 49-bit register. The apparent energy register

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

equivalent to integration in continuous time. Equation 29

expresses this relationship.

⎪⎭

⎪

⎬

⎫

⎪⎩

⎪

⎨

⎧

∑

∞

→

)

(

Power

Apparent

Lim

Energy

Apparent

(27)

where:

is the discrete number of time samples.

is the time sample period.

The discrete time sample period (T) for the accumulation

Figure 66 shows this discrete time integration or accumulation.

The apparent power signal is continuously added to the internal

energy always remains positive in theory.

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

value in the VADIV register is 0, then the internal active energy

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

long) is provided to read the apparent energy. This register is

reset to 0 after a read operation.

Figure 67 shows this apparent energy accumulation for full-

scale signals (sinusoidal) on the analog inputs. The three curves

illustrate the minimum time for the energy register to roll over

when the VAGAIN registers content is equal to 0x7FF, 0x000,

and 0x800. The VAGAIN register is used to carry out an

apparent power calibration. As shown in the figure, the fastest

integration time occurs when the VAGAIN register is set to

maximum full scale, i.e., 0x7FF.

VADIV

APPARENT

POWER

VAENERGY[23:0]

APPARENT POWER IS

ACCUMULATED (INTEGRATED) IN

THE APPARENT ENERGY REGISTER

TIME (nT)

ACTIVE POWER

SIGNAL = P

Figure 66. Apparent Energy Calculation

0xFF FFFF

0x80 0000

0x40 0000

0x20 0000

0x00 0000

VAENERGY[23:0]

6.26

12.52

18.78

25.04

TIME

(minutes)

VAGAIN = 0x7FF

VAGAIN = 0x000

VAGAIN = 0x800

Figure 67. Energy Register Rollover Time for Full-Scale Power

(Maximum and Minimum Power Gain)

Note that the apparent energy register is unsigned—see Figure

67. By using the interrupt enable register, the ADE7763 can be

configured to issue an interrupt (IRQ) when the apparent energy

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.

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