Calculation of phase angle?

[metalboy]

Hi there,

Just a fundamental question which i hope someone may have the time to answer. I'm trying to do some complex number calculations. I'm not really familiar with this but have found some good tutorials and so have do ok so far! My question is: Is it possible to find the phase angle by knowing only the voltage, current and frequency in an AC analysis? The calculations which I've done so far have had the a + jb parts and so i've been able to find the phase angle - but not this time. I have a frequency of 70Hz, supply current of 212A and a voltage of 317V.Any help / hints would be appreciated!

Thanks,
m.

 

[edison123]

Hint: Power factor

*Why a man thinks he outrun a chasing dog when it has twice as many legs?*

 

[metalboy]

Hello edison123,

Thanks for your reply. OK, i've been doing some investigative work into power factors but i'm a bit confused. From what i can gather, i have a voltage and a current which enables me to calculate the 'apparent power'. However, i'm not sure how to go about calculating the voltage from the resistor and inductor which is necessary to find the phase angle. Can this information be found from the things i posted earlier, or would it depend on the machinery being powered etc?

Thanks again,
m.

 

[edison123]

If you have values of resistance R and Inductance L,

Impedance of the Inductance is = X = 2*pi*f*L

Total Impedance = Z = sqrt(R*R + X*X)

Power factor = R/Z

If this is a homework, this thread will be deleted by forum managers.


*Why a man thinks he outrun a chasing dog when it has twice as many legs?*

 

[metalboy]

no its not a homework question.

ok, thats great thanks, i'll give it a try and get back..

 

[waross]

Be aware that some components exhibit different apparent "R" on AC as compared to your simple solution.
Skin effect and different hysteresis of magnetic cores at different frequencies are two of the culprits.
Expect several percent error when checking your calculations experimentally in the lab.
respectfully