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ADE7752 Fiches technique(PDF) 9 Page - Analog Devices |
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ADE7752 Fiches technique(HTML) 9 Page - Analog Devices |
9 / 10 page REV. PrB 08/01 –9– PRELIMINARY TECHNICAL DATA ADE7752 () () + ⋅ ⋅ ⋅ + ⋅ ⋅ − + ⋅ ⋅ + ⋅ ⋅ ⋅ + ⋅ ⋅ − ⋅ ⋅ = − × − + − × − = 3 2 cos 2 3 4 cos 2 3 2 cos 2 cos 2 3 4 cos 2 cos 2 ) ( ) ( ) ( ) ( π ω π ω π ω ω π ω ω t I t V t V t I t V t V P IBN IBP VC VB IAN IAP VC VA P l B l C l B l A l C l A For simplification, we assume that φA = φB = φC = 0 and VA = VB =VC = V. The equation above becomes: () () + ⋅ + ⋅ ⋅ ⋅ ⋅ + ⋅ + ⋅ ⋅ ⋅ ⋅ = 3 2 cos sin 3 sin 2 cos 3 2 sin 3 2 sin 2 π ω π ω π ω π ω π t t I V t t I V P l l B l l A (9) P then becomes: + + ⋅ ⋅ + + + ⋅ ⋅ = 3 2 sin 3 sin 3 2 2 sin 3 2 sin π ω π π ω π t I V t I V P l B BN l A AN (10) Where: VAN = V . sin(2 π/3) represents the RMS voltage between VAP and VN pins of the ADE7752 VBN = V . sin ( π/3) represents the RMS voltage between VBP and VN pins of the ADE7752. As the LPF on each channel eliminates the 2 ω l component of the equation, the Real power measured by the ADE7752 is: 2 3 2 3 ⋅ ⋅ + ⋅ ⋅ = B BN A AN I V I V P Where: VAN and VBN are the voltage RMS at the voltage inputs of the ADE7752 after voltage sensing IA and IB are the voltage RMS at the current input of the ADE7752 after current sensing If full scale AC voltage of ±125 mV peak are applied to the Voltage channels and Current channels, the expected output frequency is calculated as follows: F1–5 = 0.596 Hz, SCF = S0 = S1 = 1 VAN = VBN = IA = IB = 125 mV peak AC = 0.125/ 2 volts rms VCN = IC = 0 VREF = 2.5 V (nominal reference value). NOTE: If the on-chip reference is used, actual output frequencies may vary from device to device due to reference tolerance of ±8%. 14 . 0 2 3 5 . 2 2 2 596 . 0 125 . 0 125 . 0 2 . 109 2 2 = × × × × × × × = Freq Table III shows a complete listing of all maximum output frequencies when using all three channels inputs. Table III. Maximum Output Frequency on F1 and F2 Max Frequency Max Frequency SCF S1 S0 for DC Inputs (Hz) for AC Inputs (Hz) 1 1 1 0.48 0.24 0 1 1 62.52 31.26 - 1 0 15.6 7.8 - 0 1 3.9 1.95 - 0 0 0.96 0.48 Frequency Output CF The pulse output CF (Calibration Frequency) is intended for use during calibration. The output pulse rate on CF can be up to 160 times the pulse rate on F1 and F2. The lower the F1–5 frequency selected, the higher the CF scaling. Table IV shows how the two frequencies are related, depending on the states of the logic inputs S0, S1 and SCF. Because of its relatively high pulse rate, the frequency at this logic output is proportional to the instantaneous real power. As is the case with F1 and F2, the frequency is derived from the output of the low-pass filter after multiplication. However, because the output frequency is high, this real power information is accumulated over a much shorter time. Hence less averaging is carried out in the digital-to-frequency conversion. With much less averaging of the real power signal, the CF output is much more responsive to power fluctuations—see Signal Processing Block in Figure 8. Table IV. Maximum Output Frequency on CF SCF S1 S0 F1–5 (Hz) CF Max for AC Signals (Hz) 0 0 0 1.19 160 x F1, F2 = 78.12 1 0 0 1.19 8 x F1, F2 = 3.90 0 0 1 4.77 160 x F1, F2 = 312.51 1 0 1 4.77 16 x F1, F2 = 31.26 0 1 0 19.07 16 x F1, F2 = 130.56 1 1 0 19.07 8 x F1, F2 = 62.49 0 1 1 76.29 8 x F1, F2 = 250 1 1 1 0.596 16 x F1, F2 = 3.90 Hz Frequency Outputs Figure 1 shows a timing diagram for the various frequency outputs. The outputs F1 and F2 are the low frequency outputs that can be used to directly drive a stepper motor or electromechanical impulse counter. The F1 and F2 outputs provide two alternating high going pulses. The pulsewidth (t1) is set at 275 ms and the time between the rising edges of F1 and F2 (t3) is approximately half the period of F1 (t2). If however the period of F1 and F2 falls below 550 ms (1.81 Hz) the pulsewidth of F1 and F2 is set to half of their period. The maximum output frequencies for F1 and F2 are shown in Table III. The high frequency CF output is intended to be used for communications and calibration purposes. CF produces a 90 ms-wide active high pulse (t4) at a frequency proportional to active power. The CF output frequencies are given in Table IV. As in the case of F1 and F2, if the period of CF (t5) falls below 180 ms, the CF pulsewidth is set to half the period. For example, if the CF frequency is 20 Hz, the CF pulsewidth is 25 ms. |
Numéro de pièce similaire - ADE7752 |
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Description similaire - ADE7752 |
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