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ADE7768 数据表(PDF) 11 Page - Analog Devices |
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ADE7768 数据表(HTML) 11 Page - Analog Devices |
11 / 20 page ADE7768 Rev. A | Page 11 of 20 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. ( h 0 h h 0 α t hω V V t v + × × + = ∑ ∞ ≠ sin 2 ) ( ) (2) where: v(t) is the instantaneous voltage. V0 is the average value. Vh is the rms value of voltage harmonic h. i s the phase angle of the voltage harmonic. h α ( ∑ ∞ ≠ + × × + = o h h h O β t h I I t i ω sin 2 ) ( ) (3) where: i(t) is the instantaneous current. I0 is the dc component. Ih is the rms value of current harmonic h. is the phase angle of the current harmonic. h β 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: (4) 1 cos φ 1 1 1 I V P × = 1 1 1 β α φ − = and (5) h h 1 h h H I V P φ cos × = ∑ ∞ ≠ h h h β α φ − = 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. 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. +30mV –30mV VCM V1 DIFFERENTIAL INPUT ±30mV MAX PEAK COMMON-MODE ±6.25mV MAX V1P V1N V1 VCM 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. +165mV –165mV VCM V2 DIFFERENTIAL INPUT ±165mV MAX PEAK COMMON-MODE ±25mV MAX V2P V2N V2 VCM 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. |
类似零件编号 - ADE7768 |
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类似说明 - ADE7768 |
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