Hi all,

I am using ade7880 for energy metering.I am using a** CT with max input current 63A and ratio is 1:252**

To calculate values of registers like **WTHR, VARTHR, VATHR, VLEVEL ****and VNOM**, we require following values:

**U,Ufs,I,Ifs**.

Firstly i have a doubt what is U,Ufs,I,Ifs?

In my opinion :

**U->**nominal rms phase voltage (which i need to decide** 220V/110V rms**)

**I->**Nominal rms phase current (i need to decide--- say **10A rms**)

**Ifs->**rms phase current for full scale adc input(**63/root2---rms**)

**Ufs->?How to calculate Ufs?**

**Acc to datasheet -->Ufs and Ifs are rms values of phase voltages and currents when the ADC inputs are at full scale**.

**and U and I are nominal rms values.**

Secondly:

How to choose **The meter constant (MC, in impulses/kWh)-1600/3200/4800**/arbitrary?

Thirdly,What is the **value of constant----- n------** used in calculation of **WTHR, VARTHR, VATHR?**

Please help me with the above issues and let me know where i am wrong?

Thanks

Anurag

Hi anur

Please find below the answers to your questions:

1.I accept with your understanding of U and I. Ufs and Ifs are the full scale voltage and current respectively when the ADC inputs are at full scale, i.e., + 500 mV. Usually, one sets this to be the maximum possible voltage and current in their application. It depends upon your attenuation network and CT ratio. For which current/voltage, the input to the IC is + 500 mV, that current/voltage is the Ifs/Ufs.

2. Generally MC is a target figure to which meter manufacturers adhere to. If you do not have such a target, pick one arbitrarily and try to use it uniformly in all your calculations.

3. n for WTHR corresponds to the degree multiple of Wh that one LSB of WATTHR represents. Say, if you need to assign weights to WATTHR register such that one LSB is in KWh or 10^3 Wh, then n is 3. It is a similar logic for 'n' in all other equations as well.

Regards

hmani