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ADE7880 KWATT, KVAR, PF in Delta Mode

Question asked by Glenn_Wilson on Dec 27, 2016

I would LOVE Ap-Note 639 or other to show how to get KWATT, KVAR, and PF in Delta Mode.

I have worked on this for months and must not be as smart as most people .

At the moment, I do have the complete 3-phase Delta system Corner-grounded.

I have phase A and C currents feeding A and C currents through CTs.

Voltages A & C likewise go into Neutral.

B goes into Neutral (and B is of course grounded).

the B Voltage input is grounded near the ADE7880.

Voltage and Current have measured correctly for a long time.

I calibrated the power gains in wye mode so they worked but of course the individual AWATT, BWATT, CWATT, AVA, BVA, CVA, APF, BPF, and CPF all seem to be messed up in Corner Grounded mode - per figure 15.3.

I read somewhere to use FWATT and VFA.

This seems to give GREAT results and PF seems like it might be correct by dividing FWATT by FVA.

I used the cosine rule and measured the angle between A and C volts and calculated V(a-c) this works well.

All seems well but the magnitude of FWATT is definitely too large (330 when it should be 138).

Are FWATT and FVA ok to use in Delta Mode 15.3 configuration?

I also see where you need to measure angles between voltage and current.

I know how to do this - but can't do it real time like the ADE7880 needs to.

To sum it up, I am wired per 15.3 Delta Mode CONSEL = 0x01.

   I have read AVRMS 0x43C1 and obtained correct V(a-b) voltage.

   I have read CVRMS 0x43C5 and obtained correct V(b-c) voltage.

   I have set the angle to 0b01 and read the correct angle between V(a-b) and V(b-c).

   I have used the law of cosines A^2 = B^2 + C^2 -2ABcos(A) and correctly calculated V(a-c).

   I have read AIRMS 0x43C0 and obtained correct A current.

   I have read CIRMS 0X43C4 and obtained correct C current.

   I have not yet fought through calculating B current but believe I can.

   I have read FWATTS - these seem proportionally correct but wrong (2.4 times to large)

   I have read FVA - this again, seems proportionally correct but wrong (2.4 times to large)

   I've used pythagorean theorem to obtain VARS - seems reasonable relative to FWATTS and FVA.

   Dividing VWATTS but FVA seems to work - gives correct polarity and perhaps correct value for a motor,

capacitor and resistive load.

May I use FVA and FWATTS to derive total Watts, total VA, total VAR, and PF?

Thanks, Glenn Wilson wilson@stny.rr.com

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