What is Phasor diagram: Definition and 24 Discussions

In physics and engineering, a phasor (a portmanteau of phase vector), is a complex number representing a sinusoidal function whose amplitude (A), angular frequency (ω), and initial phase (θ) are time-invariant. It is related to a more general concept called analytic representation, which decomposes a sinusoid into the product of a complex constant and a factor depending on time and frequency. The complex constant, which depends on amplitude and phase, is known as a phasor, or complex amplitude, and (in older texts) sinor or even complexor.A common situation in electrical networks is the existence of multiple sinusoids all with the same frequency, but different amplitudes and phases. The only difference in their analytic representations is the complex amplitude (phasor). A linear combination of such functions can be factored into the product of a linear combination of phasors (known as phasor arithmetic) and the time/frequency dependent factor that they all have in common.
The origin of the term phasor rightfully suggests that a (diagrammatic) calculus somewhat similar to that possible for vectors is possible for phasors as well. An important additional feature of the phasor transform is that differentiation and integration of sinusoidal signals (having constant amplitude, period and phase) corresponds to simple algebraic operations on the phasors; the phasor transform thus allows the analysis (calculation) of the AC steady state of RLC circuits by solving simple algebraic equations (albeit with complex coefficients) in the phasor domain instead of solving differential equations (with real coefficients) in the time domain. The originator of the phasor transform was Charles Proteus Steinmetz working at General Electric in the late 19th century.Glossing over some mathematical details, the phasor transform can also be seen as a particular case of the Laplace transform, which additionally can be used to (simultaneously) derive the transient response of an RLC circuit. However, the Laplace transform is mathematically more difficult to apply and the effort may be unjustified if only steady state analysis is required.

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  1. P

    MATLAB Phasor diagram - how to check angle in matlab?

    I have a problem with checking angle in phasor diagram. I print my phasor diagram and I don't know how to check angle in window. Have somebody any idea how to search that? Maybe it is not possible and I need to add function in my MATLAB code to get result.
  2. Cassy85

    Create a Phasor Diagram Easily: Step-by-Step Guide & Helpful Tips

    Hi, I'm struggling to find out how to create a phasor diagram. I have attached a photo of the question any help would be greatly appreciated. This is what I have attempted so far. It's question 2b I am really struggling with. I'm not looking for the answers just looking for some direction...
  3. nobodyjusttrying

    Create a Phasor Diagram for Steady State Circuits

    So all we have to do is find the current and power distribution in the steady state circuit. Create a phasor diagram. I don't exactly know how to tell it in english, but i think there is a thing I called c. & p. paths.
  4. B

    Engineering RLC Series Network: Impedance, Current, Power Factor, Phasor Diagram

    Hello. I have completed the following question. My answer: i) Circuit Impedance Reactance = XL = 2 x pi x F x L = 2 x pi x 50 x 0.15 = 47.12 Ohms Reactance of Capacitor = XC = 1/2 x pi x F x C...
  5. C

    What will the phasor diagram of this LCR circuit looks like?

    I know the current of capacitor and inductor must be parallel but pointing in opposite direction due to the fact they are connected in parallel thus having same voltage (please see attached screenshots). The current of resistor will simply be the sum of these two vectors, but what about its...
  6. Peter Alexander

    Understanding Transformer Phasor Diagrams: A Step-by-Step Guide

    Hello everyone! I'm currently studying transformers and a task related to phasor diagrams shows up. I'm having lots of problems with comprehension of the subject, so I'd like to ask for some help. I don't understand how the phasor diagram given as a solution could possibly be drawn out of the...
  7. J

    Power System Fault Phasor Diagram

    Homework Statement Homework Equations If load is inductive current lags voltage. If load is capacitive voltage lags current The Attempt at a Solution Current lags voltage since wire is inductive. So IF1 lags VF1 and IF2 lags VF2 But book says answer is C Why should VF1 lag IF1? This will...
  8. J

    Autotransformer phasor diagram

    I'm studying Auto Transformer phasor diagram, and am having some doubts. I'd be grateful if someone could help me out with them. Book has equation: I understand that using Kirchoff's law we get minus sign for (I2 - I1) term, but shouldn't it be positive as per concept? Negative sign means the...
  9. doktorwho

    Help understanding phasor solution

    Homework Statement From the given circuit and provided information draw a phasor and calculate the inductance. Homework Equations 3. The Attempt at a Solution [/B] The paper was given to me at class as a solution to our homework and i can't understand how they drew the phasor and drew the...
  10. J

    Engineering Synchronous Motor Phasor Diagram

    It's not really a problem but I was studying Sync Motors for assignment and didn't understand few things. 1. Homework Statement http://s1320.photobucket.com/user/ajaytulsiani/media/-%20ia_zps8oujbzrh.jpg.html http://s1320.photobucket.com/user/ajaytulsiani/media/synch_zps3bry0aah.jpg.html In...
  11. L

    Synchronous generator phasor diagram

    1. Problem Statement: A 4-pole, star-connected, 50 Hz, 11kV, 40 MVA turbogenerator, with a synchronous reactance of 0.8 p.i., is connected to a power network. This power network can be represented by 11-kV infinite bus with a series reactance of j 0.5 Ω. A voltage regulator adjusts the field...
  12. S

    Phase Difference between Voltage and Current

    Homework Statement The circuit above has a 29 resistor and a 11.1 mH inductor. Calculate the theoretical phase difference between the current CPA and voltage VPB if the circuit is driven by a sinusoidal voltage source with a peak amplitude of 3.5 V at the following frequencies: 20 Hz 420 Hz...
  13. M

    Need explanations about phasor diagram

    How do we know that the phase of I1 is faster than I0? And how do we know that I3 is faster than I2? How do we know that I2 is the slowest of them all??
  14. F

    Basic Trigonometry - Phasor Diagram

    Homework Statement Hello everyone, I am having difficulty with something that should be very basic knowledge for most engineers here. I cannot see how this trigonometric relationship is being made from the phasor diagram I attached... I remember the SohCahToa rule, but it's just not...
  15. S

    Phasor Diagram of No Load Ideal Transformer

    For a no load ideal transformer V1 is anti phase with E1? or in phase like this?
  16. G

    Engineering Parallel RLC circuit phasor diagram

    I am having difficulties with phasor diagram for Is and Vs of an parallel RLC circuit. I have calculated all values but not sure how to use phasors. Impedance Z has angle +65°. Current Isupply +30° and Vsupply is Z*Is= Vs at angle 95° But with parrallel network V is the reference so I guess it...
  17. J

    Three phase system phasor diagram

    Can anyone with knowledge of three phase system please explain the concept behind phasor diagrams and how to draw one based off given phase angles for both current and voltage? Thanks in advance for your time.
  18. I

    Understanding the Phases in the Double-Slit Experiment

    1. Homework Statement and all the rest This is from a take home exam we already had graded. Professor does not mark our papers or review and we have no tutors. :( Can someone point where I went wrong? The blues are the few markings he made that I went over again and the orange...
  19. S

    Engineering Phasor Diagram RLC Series AC Circuit

    Homework Statement I'm struggling to figure out what vectors I use for my phasor diagram for an RLC series circuit. Homework Equations VC = 1/j\omegaC VL = j\omegaL VR = IZ The Attempt at a Solution I know how to add vectors, so that's not a problem, transfer my circuit from the time...
  20. M

    Calculating Impedance and Drawing a Basic Phasor Diagram

    Homework Statement I have attached the problem and all my work. If someone can check my work for part a, that would be great. As far as part b, I need the most help here. Finally for part c, I think my work so far is correct, but I need help to graph it. Thank you in advance. Homework...
  21. C

    Finding voltage across elements in phasor diagram,

    Finding voltage across elements in phasor diagram, URGENT! Hi there, first time posting here, just caught up on a question with no worked solutions and it's driving me crazy! I've attached the question below,and the answer to b is v(t)= 5cos(2t-112). I can do part a but am struggling on...
  22. C

    Drawing a Balanced 3-Phase Resisitve-Capacitive Load Phasor Diagram

    Homework Statement From this diagram (see the attachment) I have to draw the phasor diagram showing the various voltages and current of balanced 3-phase resistive-capacitive load. Homework Equations I know from the capacitive current lead voltage by 90 degree The Attempt at a Solution...
  23. R

    Power Factor and Phasor Diagram

    OK, Hello! Have to make sure as I felt like I knew my stuff but failed my first exam, am I on the right tracks? Power Factor = Cosine of phase angle Phase angle = Tan Inverse ((XL-Xc)/R) (So you know) XL= Inductive Reactance Xc= Capacitive Reactance R = Resisstance Am I...