CS5467 datasheet(16/46 Pages) CIRRUS

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CS5467

DS714F3

4.8 Power and Energy Results

The instantaneous voltage and current samples are

multiplied to obtain the instantaneous power (P1, P2)

(see Figure 3 and 4). The product is then averaged over

conversions to compute active power (P1AVG,

P2AVG).

Apparent power (S1, S2) is the product of RMS voltage

and current as shown:

Power factor (PF1, PF2) is active power divided by ap-

parent power as shown below. The sign of the power

factor is determined by the active power.

Wideband reactive power (Q1WB, Q2WB) is calculated

by doing a vector subtraction of active power from ap-

parent power.

Quadrature power (Q1, Q2) are sample rate results ob-

tained by multiplying instantaneous current (I1, I2) by in-

stantaneous quadrature voltage (V1Q, V2Q) which are

created by phase shifting instantaneous voltage (V1,

) 90 degrees using first-order integrators. (See Fig-

ure 3 and 4). The gain of these integrators is inversely

related to line frequency, so their gain is corrected by

the Epsilon register, which is based on line frequency.

Reactive power (Q1Avg, Q2AvG) is generated by inte-

grating the instantaneous quadrature power over N

samples.

Active power (P1AVG, P2AVG), apparent power (S1, S2),

and reactive power (Q1AVG, Q2AVG) of the two channels

are summed up and then divided by 2. The calculation

results are placed in EPULSE, SPULSE, and QPULSE reg-

isters which can be configured to drive energy pulse

outputs. (See Figure 6.)

V1ACOFF

(V2ACOFF)

I1ACOFF

(I2 ACOFF)

P1OFF(P2OFF)

Figure 5. Low-rate Calculations

RMS



Active

------------------

Active

–

P1AVG

÷2

P2AVG

EPULSE

EACCM

OVF=

÷2

SPULSE

SACCM

OVF=

Q1AVG

÷2

Q2AVG

QPULSE

QACCM

OVF=

PulseRate

( E1, E2, E3 )

Figure 6. Two-channel Power Summation

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