ADE7768ARZ-RL データシートの表示（PDF） - Analog Devices

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ADE7768ARZ-RL

Energy Metering IC with Integrated Oscillator and Positive Power Accumulation

Analog Devices 

Nonsinusoidal Voltage and Current

The real power calculation method also holds true for non-

sinusoidal current and voltage waveforms. All voltage and

current waveforms in practical applications have some

harmonic content. Using the Fourier transform, instantaneous

voltage and current waveforms can be expressed in terms of

their harmonic content.

( ) ∞

v(t) = V0 + 2 × ∑Vh × sin hωt + αh

(2)

h≠0

where:

v(t) is the instantaneous voltage.

V0 is the average value.

Vh is the rms value of voltage harmonic h.

αh is the phase angle of the voltage harmonic.

i(t) = IO +

2

×

∞

∑Ih

×

sin(hω t

+

βh

)

(3)

h≠o

where:

i(t) is the instantaneous current.

I0 is the dc component.

Ih is the rms value of current harmonic h.

βh is the phase angle of the current harmonic.

Using Equations 2 and 3, the real power (P) can be expressed in

terms of its fundamental real power (P1) and harmonic real

power (PH) as P = P1 + PH

where:

P1 = V1 × I1 cos φ1

(4)

φ1 = α1 − β1

and

∞

PH = ∑Vh × Ih cos φh

(5)

h≠1

φh = αh − βh

In Equation 5, a harmonic real power component is generated

for every harmonic, provided that harmonic is present in both

the voltage and current waveforms. The power factor calcul-

ation has previously been shown to be accurate in a pure

sinusoid. Therefore, the harmonic real power must also

correctly account for the power factor, because it is made up

of a series of pure sinusoids.

Note that the input bandwidth of the analog inputs is 7 kHz at

the nominal internal oscillator frequency of 450 kHz.

ADE7768

ANALOG INPUTS

Channel V1 (Current Channel)

The voltage output from the current sensor is connected to the

ADE7768 here. Channel V1 is a fully differential voltage input.

V1P is the positive input with respect to V1N.

The maximum peak differential signal on Channel V1 should

be less than ±30 mV (21 mV rms for a pure sinusoidal signal)

for specified operation.

V1

+30mV

VCM

DIFFERENTIAL INPUT

±30mV MAX PEAK

COMMON-MODE

±6.25mV MAX

V1P

V1 V1N

VCM

–30mV

AGND

Figure 18. Maximum Signal Levels, Channel V1

Figure 18 shows the maximum signal levels on V1P and V1N.

The maximum differential voltage is ±30 mV. The differential

voltage signal on the inputs must be referenced to a common

mode, such as AGND. The maximum common-mode signal is

±6.25 mV.

Channel V2 (Voltage Channel)

The output of the line voltage sensor is connected to the device

at this analog input. Channel V2 is a fully differential voltage

input with a maximum peak differential signal of ±165 mV.

Figure 19 shows the maximum signal levels that can be

connected to the ADE7768 Channel V2.

V2

+165mV

VCM

DIFFERENTIAL INPUT

±165mV MAX PEAK

COMMON-MODE

±25mV MAX

V2P

V2 V2N

VCM

–165mV

AGND

Figure 19. Maximum Signal Levels, Channel V2

Channel V2 is usually driven from a common-mode voltage,

that is, the differential voltage signal on the input is referenced

to a common mode (usually AGND). The analog inputs of the

ADE7768 can be driven with common-mode voltages of up to

25 mV with respect to AGND. However, best results are

achieved using a common mode equal to AGND.

Rev. A | Page 11 of 20

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