1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

How do i calculate these phaors?

  1. Jun 20, 2012 #1
    First! i am taking a course called poly phase in electrical - control systems and i didn't take the math course prerequesite for it...i am completely stuck and have no idea what I'm doing!

    The lab was- Measure and record the following as magnitudes not as phasors

    It= 1.189
    L1= 1.158
    L2 = 0.633
    Source Voltage =100v
    Voltage across inductance load VL= 68.13v
    Voltage across Resistance Load R1 = 68.10v
    Voltage across capacitance load Vc= 94.88
    The Voltage Across the resistance load R2=35.90
    Total power Pt= 117.96
    Power over inductance load P1=10.46
    Power over capacitance load P2= 107.5

    Assume the following Values for calculation process
    Ac Freq = 60Hz
    XL = 100mH
    Re = 100 ohms
    Xc= 0.18 micro farad
    R1 = 60 ohm
    R2 = 60 ohm



    The question is

    Assume Vt = 100 < 0degree, calculate, showing steps, the current phasor L1.



    note: I've read that you guys HELP not DO my homework so if you can use the same idea and give me different numbers to understand he calculation i can do it my self, i just don't know where to start
     
    Last edited by a moderator: Jun 20, 2012
  2. jcsd
  3. Jun 20, 2012 #2

    berkeman

    User Avatar

    Staff: Mentor

    Welcome to the PF.

    You will need to provide a diagram, and define your terms better please. L1 is a current?
     
  4. Jun 20, 2012 #3
    image.jpg
    Thank you!

    Sorry, i realized i didn't put unites on my numbers :P. Here is the corrected version::



    It= 1.189 amps
    L1= 1.158 amps
    L2 = 0.633 amps
    Source Voltage =100v
    Voltage across inductance load VL= 68.13v
    Voltage across Resistance Load R1 = 68.10v
    Voltage across capacitance load Vc= 94.88 volts
    The Voltage Across the resistance load R2=35.90 volts
    Total power Pt= 117.96 volts
    Power over inductance load P1=10.46 Watts
    Power over capacitance load P2= 107.5 Watts

    Assume the following Values for calculation process
    Ac Freq = 60Hz
    XL = 100mH
    Re = 100 ohms
    Xc= 0.18 micro farad
    R1 = 60 ohm
    R2 = 60 ohm
     
  5. Jun 20, 2012 #4

    berkeman

    User Avatar

    Staff: Mentor

    I think what you are calling L1 and L2 are actually I1 and I2. And the units of Xc are Ohms, not uF.

    Just think of it as a simple resistive circuit and solve for the currents in the two branches. The only difference is that you will use complex numbers for the impedances, instead of just real numbers for resistances.

    Show us a start at writing the KCL for the top node...
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook