ADE7758ARWRL datasheet(45/68 Pages) AD

45 / 68 page

ADE7758

Rev. A | Page 45 of 68

The AWG value is calculated to be 84 d using Equation 33,

which means the value 0x3F should be written to AWG.

0244

–

xWG

Phase Calibration Using Pulse Output

The ADE7758 includes a phase calibration register on each

phase to compensate for small phase errors. Large phase errors

should be compensated by adjusting the antialiasing filters. The

ADE7758’s phase calibration is a time delay with different

weights in the positive and negative direction (see the Phase

Compensation section). Because a current transformer is a

source of phase error, a fixed nominal value may be decided on

to load into the xPHCAL registers at power-up. During

calibration, this value can be adjusted for CT-to-CT error.

Figure 78 shows the steps involved in calibrating the phase

using the pulse output.

START

ALL

PHASES

PHASE ERROR

CALIBRATED?

END

YES

STEP 1

SET UP PULSE

OUTPUT FOR

PHASE A, B, OR C

AND ENABLE CF

OUTPUTS

STEP 2

SET UP SYSTEM

FOR ITEST, VNOM,

PF = 0.5

STEP 3

MEASURE %

ERROR IN APCF

STEP 4

CALCULATE PHASE

ERROR (DEGREES)

STEP 5

PERIOD OF

SYSTEM

KNOWN?

MEASURE

PERIOD USING

FREQ REGISTER

YES

CALCULATE AND

WRITE TO

XPHCAL

Figure 78. Phase Calibration Using Pulse Output

Step 1: Step 1 and Step 3 from the gain calibration should be

repeated to configure the ADE7758 pulse output.

Step 2: Set the test system for ITEST, VNOM, and 0.5 power factor.

Step 3: Measure the percent error in the pulse output, APCF,

from the reference meter using Equation 31.

Step 4: Calculate the Phase Error in degrees using the following

equation:

()

⎟⎟

⎠

⎞

⎜⎜

⎝

⎛

sin

Arc

–

ERROR

Error

Phase

(35)

Step 5: Calculate xPHCAL

()

Error

Phase

Period

μs

xPHCAL

360

–

(36)

If it is not known, the period is available in the ADE7758’s

frequency register, FREQ (0x10). Equation 37 shows how to

determine the value that needs to be written to xPHCAL using

the period register measurement. In Equation 37, the 2.4 µs is

for phase errors that are negative. For positive phase errors, the

2.4 µs is replaced by 4.8 µs (see the Phase Compensation

section).

[]

FREQ

Error

xPHCAL

⎟⎟

⎠

⎞

⎜⎜

⎝

⎛

360

sin

Arc

(37)

Example—Phase Calibration of Phase A Using Pulse Output

For this example, ITEST = 10 A, VNOM = 220 V, VFULLSCALE = 500 V,

IFULLSCALE = 130 A, MC = 3200 impulses/kWh, Power Factor = 0.5

inductive, and Frequency = 50 Hz.

With ITEST, VNOM, and 0.5 inductive power factor, the example

ADE7758 meter shows 0.9821Hz on the pulse output. This is

equivalent to 0.215% error from the reference meter value using

Equation 31.

The Phase Error in degrees using Equation 35 is −0.07°.

()

⎟⎟

⎠

⎞

⎜⎜

⎝

⎛

–

00215

sin

Arc

–

Error

Phase

If at 50 Hz the FREQ register = 2083d, the value that should be

written to APHCAL (0x15) is 0x15 using Equation 37.

2083

360

APHCAL

Power Offset Calibration Using Pulse Output

Power offset calibration should be used for outstanding

performance over a wide dynamic range (1,000:1). Calibration

of the power offset is done at or close to the minimum current

where the desired accuracy is required. The ADE7758 has

power offset registers for watts and VAR (xWATTOS and

xVAROS). Offsets in the VA measurement are compensated by

adjusting the rms offset registers (see the Calibration of IRMS

and VRMS Offset section). Figure 79 shows the steps to

calibrate the power offsets using the pulse outputs.

ADE7758ARWRL 数据表(PDF) 45 Page - Analog Devices

ADE7758ARWRL 数据表(HTML) 45 Page - Analog Devices

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68

数据表下载

链接网址

ADE7758ARWRL 数据表(PDF) 45 Page - Analog Devices

ADE7758ARWRL 数据表(HTML) 45 Page - Analog Devices

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68

数据表 下载

链接网址

数据表下载