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

----------------------------
------------
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.

No, this is a single phase experiment. But, we got extremely high
values of voltage for A phase compared to B and C phases. I need to
calculate the real and apparent power for the values which i think is
P=V*I*cos(power factor) and Q=VIsin(power factor) where power
factor=cosine(angle V- angle I), right? I am confused because this is a
single phase experiment, so do I need to calculate the p.f. and power
for only the A phase and not take into consideration the other two
phases? Thanks again, Farah.
D> I assume that this is the first experiment with 3 phase, not single phase.

----------------------------
-----------------------
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?

PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.