How do i calculate these phaors?

  • Thread starter cbengineering
  • Start date
In summary, the current in the left branch is 1.189 amps and the current in the right branch is 1.158 amps.
  • #1
cbengineering
2
0
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:
Physics news on Phys.org
  • #2
cbengineering said:
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

Welcome to the PF.

You will need to provide a diagram, and define your terms better please. L1 is a current?
 
  • #3
image.jpg
berkeman said:
Welcome to the PF.

You will need to provide a diagram, and define your terms better please. L1 is a current?

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
 
  • #4
cbengineering said:
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

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...
 
  • #5



To calculate the phasor for L1, we first need to understand the concept of phasors and how they relate to electrical circuits. A phasor is a representation of a sinusoidal signal, such as voltage or current, in the complex plane. It is used to simplify the analysis of AC circuits by converting the time-domain signals into magnitude and phase angle in the frequency domain.

To calculate the phasor for L1, we need to use the following formula:

L1 = VL/XL

Where VL is the voltage across the inductance load and XL is the inductive reactance. In this case, we have already been given the values for VL and XL in the lab measurements. So we can substitute those values in the formula:

L1 = 68.13/100mH

Now, we need to convert the value of inductive reactance into ohms. We can do this by using the formula:

XL = 2πfL

Where f is the frequency and L is the inductance. In this case, we have been given the value for frequency (60Hz) and inductance (100mH), so we can substitute those values in the formula:

XL = 2π(60)(100mH) = 37.7 ohms

Now, we can substitute this value of XL into the previous formula to calculate the phasor for L1:

L1 = 68.13/37.7 = 1.807 < 0°

This means that the phasor for L1 has a magnitude of 1.807 and a phase angle of 0 degrees. This phasor represents the relationship between the voltage across the inductance load and the inductive reactance in the complex plane.

In summary, to calculate the phasor for L1, we used the formula L1 = VL/XL, where VL is the voltage across the inductance load and XL is the inductive reactance. We also had to convert the value of inductive reactance from mH to ohms using the formula XL = 2πfL. By substituting the given values and solving the equations, we were able to calculate the phasor for L1.
 

1. How do I calculate phasors?

To calculate phasors, you will first need to understand the concept of complex numbers. Phasors represent the magnitude and phase of a sinusoidal function, and can be represented by a complex number in rectangular form. To calculate the phasor, you will need to convert the sinusoidal function into its complex representation, and then use the appropriate formulas to find the magnitude and phase of the phasor.

2. What is the difference between a phasor and a sinusoidal function?

A phasor is a complex number that represents the magnitude and phase of a sinusoidal function. While a sinusoidal function is a mathematical representation of a waveform, a phasor is a simplified way of representing the same function in terms of its magnitude and phase, making it easier to analyze and manipulate mathematically.

3. How can phasors be used in electrical engineering?

Phasors are commonly used in electrical engineering to analyze and solve problems related to AC circuits. They allow engineers to easily calculate the magnitude and phase of voltages and currents in a circuit, making it easier to design and troubleshoot complex electrical systems.

4. Can phasors be used to analyze non-sinusoidal functions?

Yes, phasors can be used to analyze non-sinusoidal functions as well. By using Fourier series, any periodic function can be represented as a sum of sinusoidal functions, and each of these components can be represented by a phasor. This allows for the analysis of more complex electrical waveforms.

5. Are there any limitations to using phasors?

While phasors are a useful tool for analyzing AC circuits, they do have some limitations. Phasors assume that the circuit is in steady state, meaning that all voltages and currents are constant over time. They also do not take into account any non-linear components in the circuit, such as diodes or transistors, which can affect the accuracy of the analysis. Therefore, it is important to understand the limitations of phasor analysis and use it appropriately in engineering applications.

Similar threads

  • Engineering and Comp Sci Homework Help
Replies
3
Views
737
  • Engineering and Comp Sci Homework Help
Replies
26
Views
2K
Replies
2
Views
866
Replies
4
Views
1K
  • Electrical Engineering
Replies
3
Views
3K
  • Engineering and Comp Sci Homework Help
Replies
5
Views
3K
  • Electrical Engineering
Replies
1
Views
2K
  • Introductory Physics Homework Help
Replies
8
Views
2K
  • Introductory Physics Homework Help
Replies
15
Views
10K
Replies
33
Views
6K
Back
Top