ADE9178 datasheet(56/122 Pages) AD

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Data Sheet

ADE9178

APPLICATIONS INFORMATION

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Rev. A | 56 of 122

Power Gain Calibration

xPGAIN is the gain calibration register for phase x. The active and

apparent powers in each phase have a common gain register.

To configure the ADE9178, do the following steps:

1. Apply nominal voltage and current at power factor = 1.

2. Set EP_CFG = 0x15 and EGY_TIME = 999d (1 sec accumula-

tion).

3. Read the xWATTHR_SIGNED_HI register (throw away first

sample).

The expected xWATTHR_SIGNED_HI register value for nominal

inputs can be calculated as follows:

xWATTHR_SIGNED_HIEXPECTED=IFSP

×VFS_TP×POWFS_CODES

×Accumulation_Time×4000×2−13 (47)

where, IFSP is the nominal current as a fraction of full scale and

VFS_TP is the nominal voltage as a fraction of full scale.

The xPGAIN register value can be obtained as follows:

xPGAIN= xWATTHR_SIGNED_HIEXPECTED

xWATTHR_SIGNED_HIMEASURED

−1

×227

(48)

Example

With the given example system parameters, the following equations

show the calculations for APGAIN:

IFSP= 1044.188=0.22631

(49)

VFS_TP=220707=0.31117

(50)

AWATTHR_SIGNED_HIEXPECTED=0.22631

×0.31117×85829040×1×4000×2−13

=2951248 decimal

(51)

If AWATTHR_SIGNED_HIMEASURED = 2846714 decimal, then:

APGAIN= 2951248

2846714

−1 ×227=4928600

decimal=0×4B313D

(52)

Power Offset Calibration

Like the RMS offset calibration, the power offset calibration is

performed with a small current at 5000:1 or less dynamic range. In

this example, the offset calibration current is 20 mA and the voltage

is 220 V.

To configure the ADE9178, do the following steps:

1. Apply nominal voltage and offset calibration current at power

factor = 1.

2. Set EP_CFG = 0x15 and EGY_TIME = 9999d (10 sec accumu-

lation).

3. Read the xWATTHR_SIGNED_HI register (throw away first

sample).

The expected xWATTHR_SIGNED_HI register value for nominal

inputs can be calculated as follows:

xWATTHR_SIGNED_HIEXPECTED=IFSP

×VFS_TP×POWFS_CODES

×Accumulation_Time×4000×2−13 (53)

where, IFSP is the nominal current as a fraction of full scale and

VFS_TP is the nominal voltage as a fraction of full scale.

The xWATTOS register value can be obtained as follows:

xWATTOS

=xWATTHR_SIGNED_HIEXPECTED−xWATTHR_SIGNED_HIMEASURED

Accumulation

_Time×4000×2−13

Example

With the given example system parameters, the following equations

show the calculations for APGAIN:

IFSP= 0.0244.188=0.00045

(54)

VFS_TP=220707=0.31117

(55)

AWATTHR_SIGNED_HIEXPECTED=0.00045

×0.31117×85829040×10×4000×2−13

59025 decimal

(56)

If AWATTHR_SIGNED_HIMEASURED = 58134 decimal, then:

AWATTOS= 59025−58134

10×4000×2−13

182 decimal

=0×B6

(57)

Phase Calibration

It is recommended to keep the voltage channel xVPHCAL as

default value (0). To calculate xIPHCAL, apply a nominal current

and voltage at lagging power factor of 0.5, calculate phase error

from power factor xPF measured as follows:

ϕ= π3−cos−1 xPFMEASURED

227

×−1 (58)

The xIPHCAL register can be calculated as follows:

xIPHCAL=sinϕ−ω+sinω

sin2ω−ϕ

×227

, wℎere, ω

=2π×fLINE× 14000

(59)

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