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ADE7878 frequency changes afflicted  pulse error

Question asked by rajam on Nov 24, 2017
Latest reply on Nov 28, 2017 by Gary.Kang.AnalogDevices

Dear all,

In Three phase static watt hour meter we were using ADE7878 chip for measurement. Meter working voltage is 240V (+20 & -70%); Current Ib 10A ( 0.1A to 100A Imax.) and Frequency 47.5 to 52.5Hz.

 CT & Burden resistor details:

Phase current measurement: 2500 Turns (Metal enclosure);  Double burden = 3.6 + 3.6 ohm

Neutral current measurement: 1000 Turns (Plastic enclosure); Double burden = 1.2 + 1.2 ohm

 Please find attached measurement circuit for your reference.

 

As per attached test report, Meter is working fine with 50Hz frequency range & 0.5Lg, UPF

But with 47.5Hz & 52.5Hz frequency range and 0.5Lg error % goes to out of accuracy and angle also changed

                                                                                     

 

3P4W, AC STATIC WATTHOUR METER

S.No

Input Current

0.5Lg

50Hz %

47.5Hz %

52.5Hz %

ANGLE

60

57

63

1

0.5A

0.43

1.46

-0.55

2

1.0A

0.40

1.43

-0.60

3

5.0A

0.20

1.23

-0.73

4

8.0A

0.22

1.22

-0.78

5

10.0A

0.20

1.20

-0.79

6

50.0A

0.10

1.15

-0.90

7

100.0A

0.09

1.07

-0.91

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