ADE9430 datasheet(25/35 Pages) AD

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Data Sheet

ADE9430

THEORY OF OPERATION

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Rev. 0 | 25 of 35

Figure 42. Voltage Channel Datapath

RMS and Power Measurements

The ADE9430 calculates the total and fundamental values of rms

current, rms voltage, active power, reactive power, and apparent

power. The fundamental algorithm requires initialization of the net-

work frequency using the SELFREQ bit in the ACCMODE register

and the nominal voltage in the VLEVEL register. Calculate the

VLEVEL value according to the following equation:

VLEVEL = x × 1,144,084

Where x is the dynamic range that the nominal input signal is at

with respect to full scale.

For instance, if the signal is at ½ of full scale, x = 2.

VLEVEL = 2 × 1,144,084

See the ADE9430 Technical Reference Manual for additional infor-

mation.

Total and Fundamental RMS

The ADE9430 offers the total and fundamental current and voltage

rms measurements on all phase channels. The datapath is shown

in Figure 43.

Figure 43. Filter-Based Total RMS

The total rms calculations, one for each channel (AIRMS, BIRMS,

CIRMS, NIRMS, AVRMS, BVRMS, and CVRMS), are updated

every 8 kSPS. The fundamental rms calculations available in the

AIFRMS, BIFRMS, CIFRMS, AVFRMS, BVFRMS, and CVFRMS

registers are also updated every 8 kSPS. The fundamental rms is

not available for the neutral channel.

The xRMS and xFRMS value at full scale is 52,702,092 decimals.

The total and fundamental rms measurements can be calibrated for

gain and offset. Perform gain calibration on the respective current

and voltage channel datapath. The following equations indicate how

the offset calibration registers modify the result in the corresponding

rms registers:

xRMS= xRMS02+215×xRMOSOS

(4)

Where xRMS0 is the initial xRMS register value before offset cali-

bration.

xFRMS= xFRMS02+215×xFRMOSOS (5)

The ADE9430 also calculates the rms of the sum of IA + IB +

IC ± IN and stores the result in ISUMRMS. The ISUM_CFG bits

in the CONFIG0 register configure the components included in

summation.

See the ADE9430 Technical Reference Manual for additional infor-

mation.

Total and Fundamental Active Power

The ADE9430 offers total and fundamental active power measure-

ments on all channels. To calculate the total active power for Phase

A, see Figure 44.

Figure 44. Total Active Power, AWATT, Calculation for Phase A

The active power calculations, one for each channel (AWATT,

BWATT, and CWATT), are updated every 8 kSPS. The fundamental

active power is also updated every 8 kSPS and is available in the

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