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Power Measurements

Hey all, I am an undergraduate electrical engineering student and I just had my first power lab relating to single phase AC electric circuit measurements. I have a huge doubt and it would be great if someone could help me out. we measured the VAM(A phase voltage magnitude), VAP( A phase voltage phase angle), VBM, VBP, VCM, VCP,VNM,VNP, IAM (A phase current magnitude),IAP(A phase current phase angle), IBM,IBP,ICM,ICP,INM and INP (B=B phase, C=C phase, N=neutral). I need to calculate the power factor, 3*P and 3*Q , P real power and Q apparent power.

Since this is a single phase measurement, would power factor be cosine(VAP-IAP) ??? And would P be equal to VAM * IAM * cosine (p.f) and Q=VAM*IAM* sine(p.f) ? Do i need to include the B and C phases in the calculations as well?and what about the N phase?

Thanks in advance, Farah

Reply to
farah727rash
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------------ I assume that this is the first experiment with 3 phase, not single phase. You can calculate the power and power factor for each phase, A,B,C. as if you were dealing with 3 single phase systems. However the purpose of the lab is to help you understand the theory. What makes a balanced 3 phase system different from 3 single phase systems? Have you done a phasor sum of the currents A,B,C and comparedthis to the neutral current?. Are the voltages balanced? Are the currents balanced? How much unbalance? what is the sum of the phase powers. Do you know the impedances of each branch? Look at all the data you have read or calculated and compare this with what you expect from 3 phase theory. By the way there is no N phase. It is apparently a star connection.

Reply to
Don Kelly

Reply to
farah727rash

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You can look at the P,Q and power factor of each phase individually (you can sum P and Q for the total but don't try to determine pf from this as pf is definitely a per phase concept and, strictly speaking, applies to 3 phase only if all 3 phases have the same pf. I would suggest that you are also to use a bit of KCL to check the sum of the pase currents against the neutral current and milk your data for all it is worth- trying to come to some conclusions from your experiment. BUT If it is a single phase experiment, then why are you measuring 3 phases?

Could it be a lead in to polyphase considerations?

Reply to
Don Kelly

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