ADE9078ACPZ datasheet(60/108 Pages) AD

60 / 108 page

Data Sheet

ADE9078

Rev. 0 | Page 59 of 107

APPLYING THE ADE9078 TO A 3-WIRE DELTA

SERVICE

For the highest level of performance when measuring a 3-wire delta

service, connect Phase B to ground, as shown in Figure 91. For this

configuration, write VCONSEL = 001 in the ACCMODE register.

Then, VB = VA − VC and the ADE9078 calculates the VAC potential

in the BVRMS register. To calculate the current flowing through IB

from the IA and IC measurements, set ICONSEL = 1 in the

ACCMODE register so that IB = −IA − IC.

VBC 220V

90°

0.353V

90°

VBA 220V

30°

0.353V

30°

VAC 220V

150°

0.353V

150°

VCONSEL = 001

VA, VB, VC

VAP

VBP

VCP

VAN

AGND

DGND

VBN

VCN

220V

–120°

220V

120°

PHASE C

PHASE A

PHASE B

220V

0°

Figure 91. 3-Wire Delta, Phase B Connected to Ground

Note that for this 3-wire delta, Phase B connected to ground

configuration, the phasor diagram of the AV_PCF, BV_PCF, and

CV_PCF waveforms inside the ADE9078 IC, shown in Figure 92,

is shifted compared to the service diagram given in Figure 84.

CV_PCF

AI_PCF

AV_PCF

CI_PCF

BI_PCF

BV_PCF

VCONSEL = 1

180°

0°

270° LAGGING

90° LAGGING

Figure 92. Phasor Diagram of xV_PCF and xI_PCF Waveforms Inside the IC

with 3-Wire Delta with Phase B as Ground and VCONSEL = 001

To use the same PCB for both 4-wire wye and 3-wire delta circuits,

another option is to wire Phase B to the neutral terminal of the

meter, keeping the same circuit as used in Figure 89 or Figure 90.

Note that VCONSEL bits in the ACCMODE register must be

set to 001 if it is desired to obtain the VAC rms value, which is

calculated in the BVRMS register, and to use the correct phase

sequence detection method for the 3-wire delta configuration.

To calculate the current flowing through IB from the IA and IC

measurements, set ICONSEL = 1 in the ACCMODE register so

that IB = −IA − IC.

Alternatively, a series impedance can be used on Phase B, as

shown in Figure 93. This configuration can be advantageous if

an isolated power supply is used; however, it has poor performance

if the phase voltages are not balanced. Use VCONSEL = 100 with

this configuration so that VA = VA − VB; VB = VA − VC; and VC =

VC − VB. To calculate the current flowing through IB from the IA

and IC measurements, set ICONSEL = 1 so that IB = −IA − IC.

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